In my last column, I wrote about what I saw and heard on the exhibit floor at the 2026 NAB Show; this month, I’ll talk about the NAB Show’s Broadcast Engineering and IT (BEIT) Conference sessions as well as the National Television Association (formerly National Translator Association) conference in Reno, Nev., that I attended in May.

Production and streaming sessions at NAB Show focused on content creation and distribution of TV programs. However, several sessions on over-the-air transmission focused on datacasting and alternative uses for our 6-MHz RF channel beyond TV broadcasting.

As in past years, sessions were devoted to the Broadcast Positioning System, showing BPS can be a worthy backup to GPS and the progress in testing and implementation.

In “Real World Coverage Analysis of ATSC 3.0 BPS,” Jim Stenberg and Paul Shulins of Over The Air RF Consulting showed how to calculate coverage from a BPS station using their table of “BPS UHF Reception Planning Factors” (Fig. 1). A map showed excellent coverage from WHUT Washington’s BPS signal. However, the map (Fig. 2) also showed spots blocked by terrain with no coverage. As more stations transmit BPS, these spots will likely have service from another station transmitting from a different location or market.

The Case for SFNs
“Only SFNs Deliver ATSC 3.0 Everywhere: Turning Broadcast Theory into Nationwide Reality,” a presentation from Louis Libin, Sinclair’s vice president of spectrum policy and engineering, showed how important is was for broadcasters to start planning for single-frequency networks now, as coverage from a single high-power, high-tower transmission site will not provide the coverage and reliability customers expect from today’s wireless services whether consuming data or video.

“Optimizing ATSC 3.0 networks requires balancing throughput, robustness, and coverage simultaneously, reinforcing the need for architectures such as SFNs to meet the diverse and competing service requirements at the edge of coverage,” Libin said.

SFNs require additional transmitter sites, many of which are already used by other wireless services. Libin warned that broadcasters will be competing for tower space with 5G and 6G providers, and the window for securing tower access is closing. Broadcasters need to secure critical tower positions and begin building SFNs without delay or risk, as SFNs will determine broadcasting’s long-term survival.

I did not hear any mention of 5G Broadcast (the Long Term Evolution version) in any of the BEIT sessions. A more universal evolution of ATSC 3.0 into and beyond the 3GPP/5G/6G domain called B2X (aka “Broadcast-to-
Everything”) was outlined in “ATSC 3.0 and B2X Interworking with 5G Core and IP-Based Service Discovery for End-to-End Broadcast Integration” by Michael Simon, director of advanced technology at ONE Media Technologies; Rashmi Kamran, senior technical adviser at Free Stream Technologies India; and Sangsu Kim, senior director, One Media.

The Broadcast Core Network component of B2X provides the functions needed to implement a B2X Radio Access Network (BRAN) using Open Radio Access Network (O-RAN) features. Use of O-RAN allows easier interworking with other networks using O-RAN principles and interfaces and decouples hardware and software, enabling new applications and reducing obsolescence.

ATSC 3.0 offers broadcasters the opportunity to become a wireless CDN (content delivery network). In “Hybrid Media Distribution Utilizing ATSC 3.0/NextGen TV,” Yuriy Reznik, chief technology officer at Streaming Labs, compared the cost of existing CDN services and the potential revenue from an ATSC 3.0 CDN to see if it is a viable business case. The analysis studied the various available ATSC 3.0 bandwidths and coverage.

In summary, the “main result under the right conditions, ATSC 3.0 offload can deliver meaningful savings and improve one-to-many availability,” Reznik found. But the transition path matters, he noted. “Receiver penetration, gateway adoption, and an eventual ATSC 1.0 sunset could improve the economics.”

Streaming as Backup
Rather than using a broadcast station as a CDN, how about using streaming as a backup to over-the-air reception? That was the theme of “Enhancing ATSC 3.0 Service Reliability By Combining Broadcast and Broadband Services,” by Peter Gogas, director of NextGen technology at Gray Media.

A broadband fallback mode could be useful in areas where the ATSC 3.0 signal is blocked by terrain, degraded by urban multipath or receives interference, as is often the case with indoor reception of VHF channels. Implementing a combined service requires some changes to the ATSC A/331 standard. Refer to the presentation for details.

A key point: Changes would be backwards-compatible, so any ATSC 3.0 set without internet would not lose over-the-air content. Synchronizing content delivery between over-the-air and broadband will be a challenge. It requires aligning media segments and maintaining the same presentation timeline and media segment time span. Gogas recommended formatting synchronization expectations as an ATSC Recommended Practice.

Recruiting New Talent
“Finding and Engaging New Talent for Broadcast/Media Engineering,” sponsored by the Radio Club of America, was hosted by Andy Gladding, vice chair of the Society of Broadcast Engineers Chapter 15 and engineering manager for Salem Media’s New York City stations, and Bud Williamson, president and chairman of SBE Chapter 15, leader of Digital Radio Broadcasting Inc. and managing member of Neversink Media Group.

The presentation discussed the challenges facing modern broadcast engineering, including the need for “advanced knowledge of electronic, audio and/or video systems, contemporary production and studio environments, IT systems, troubleshooting skills and communication abilities” and that “pay is often lower than similar technical fields.”

It also showed how to successfully recruit new talent into broadcast engineering by enlisting the help of local college radio stations—in this case, Hofstra University’s WRHU Hempstead, N.Y. The presentation showed students making audio cables, visiting transmission facilities at the Empire State Building, and working together on projects.

Key points were “create programs that the students can drive,” “provide progress reports for the student as well as your corporate leadership team,” “publicize success,” “keep it fun!” “bring friends (your friends and their friends)” and “buy pizza.”

While the focus was on radio, the ideas shown here should work for students interested in TV as well.

The View From Reno
A few weeks after NAB Show, the National Television Association met in Reno, Nevada. This was the first time I attended, and it was a pleasure to be around so many people passionate about over-the-air television.

Mike Schmidt from Heartland Video Systems presented an option I hadn’t thought of for reducing MPEG-2 bandwidth requirements: Rather than coding HD video in MPEG-4, with the resulting compatibility issues, simply reduce the horizontal resolution by half: 960×1080.

Surprisingly, many viewers watching the half-resolution video saw little difference between it and 1920×1080 video.

I gave a presentation on the impact that interference from post-freeze LPTV applications, if granted, will have on existing full-power and low-power station viewers, particularly those near and just outside the station’s protected contour. It is available here.

Here’s a short summary of this year’s NAB Show in Las Vegas: Fewer people, smaller booths and not much new on the RF and transmission side. However, there was a lot of excitement around the launch of TV 3.0 in Brazil, with some products designed specifically for that market. In addition, there was an obvious urgency to complete the transition to ATSC 3.0.

In addition to the lack of a defined date for the end of ATSC 1.0, the major impediment to an ATSC 3.0 switch is a lack of viewers, due to a relatively small number of compatible TV sets and limited low-cost options for receiving ATSC 3.0 on existing devices.

A quick search on walmart.com revealed pages of TV sets, including a “55-inch class” Hisense model for under $200. None show ATSC 3.0/NextGen TV capability. A search for “nextgen” gave no broadcast-related results, but a search on “ATSC 3.0” did list the HDHomerun Flex and the ADTH dongle. Set-top boxes or dongles are an option, but reviews indicate that viewers find them complicated to use if they require a separate remote control.

Reception Progress
The good news from the ATSC exhibit this year was that the low-cost dongle ($70) from ADTH, along with other low-cost devices, supports reception of stations with content protection and also enables broadcast applications.

When combined with a compatible streaming box, like the Onn. 4K Pro, the ADTH dongle allows a viewer to move between NextGen TV and streaming content with the same remote. I bought one and so far, I have been happy with it.

The dongle’s off-air reception of ATSC 3.0 signals via its Saankhya Labs chipset was better than that of my Airwavz Redzone receiver with the original LG chipset, and even better than my GTMedia HDTVMate ATSC 3.0 dongle with the Sony chipset.

I was able to get perfect reception of ATSC 3.0 stations, including protected content, in Honolulu, Reno, Nev., and Los Angeles with just a whip antenna. The other dongles had problems with KCOP’s Channel 13 signal in Los Angeles, even with a better antenna.

One problem that likely applies to any device that doesn’t provide an HDMI output is that the device it is connected to must support AC-4 audio, HEVC video and Widevine Level 1 content protection (DRM). It worked great on my Samsung S24, but not on my recent Lenovo M11 tablet (which has Dolby Atmos and Widevine L1, but not AC-4). This requirement also rules out compatibility with any Apple device.

This problem has been recognized and work is underway to support multiple digital rights management (DRM) formats, like Apple’s FairPlay Streaming, as well as to provide options for devices that do not support AC-4 audio. Ideally, this can be accomplished with firmware updates instead of hardware replacement.

Transmission Requirements
While Brazil’s TV 3.0 is based on ATSC 3.0, there are some major differences in transmitter and antenna requirements. TV 3.0 uses MIMO, which splits the signal into horizontally polarized and vertically polarized components, increasing capacity. It requires a dual-polarized antenna with dual feed lines, two individual high-power amplifiers, and a modified exciter. Both Rohde & Schwarz and GatesAir had TV 3.0 transmitters available and Dielectric was showing antennas for TV 3.0.

Another major difference in TV 3.0 compared to U.S. broadcasting is Brazil has opened up new spectrum around 300 MHz for TV, which requires unique antennas. Dielectric was exhibiting its designs on the show floor. Due to the dual polarization, each transmitter will require two mask filters in addition to two HPAs, including new designs for the 300 MHz channels.

While my focus is on RF, Brazil’s TV 3.0 not only requires new antennas, transmitters and exciters, but new baseband gear. Enensys Technologies showed a complete baseband solution, from encoder output through the exciter. Triveni also showed support for TV 3.0 in its Streamscope analyzer and Guidebuilder scheduler/gateway product line.

New Gear at NAB Show
Back in the U.S., D2D was showing new firmware/software for its advanced Flex video gateway. Flex can convert an ATSC 1.0 transport stream into an ATSC 3.0 STL-TP output. The device handles transcoding, scheduler and gateway functions, providing a low-cost (under $10,000) way for an LPTV or translator operator to transmit ATSC 3.0. D2D is also working on a box to receive an ATSC 3.0 signal and retransmit it as ATSC 1.0.

This is more complicated, given that ATSC 3.0’s HEVC compression and modulation provides much greater capacity than ATSC 1.0 and MPEG-2. This will likely require either reducing the resolution of the ATSC 3.0 stream when converting HEVC to MPEG-2 or dropping some program streams.

Avateq showed a line of products to support the ATSC 3.0 Broadcast Positioning Service (BPS). (I’ll have more on BPS in part two of my NAB Show review, which will look at the Broadcast Engineering and IT Conference sessions). It is difficult to conduct mobile reception studies with ATSC 1.0 due to Doppler and multipath preventing receiver sync.

That isn’t a problem for many ATSC 3.0 configurations, and Avateq showed software that took signal data from the Avateq AVQ-200 receiver and combined it with GPS data to plot signal strength on a map. I had some suggestions on how to improve the map display, which should appear in an update.

Anywave Broadcast was hoping to show its new liquid-cooled, low-to-medium power transmitter at NAB Show, but it didn’t arrive in time. Looking at photos, the design is interesting in that it doesn’t use an outdoor heat exchanger but one incorporated into the transmitter rack. Anywave said liquid cooling is better than air in removing heat from amplifiers.

Even with the liquid-to-air exchanger, fan and pump, the new transmitter is more energy-efficient and much quieter than force-air-only cooling. Anywave also showed its exciter line, which supports both ATSC 1.0 and 3.0. It can be configured as an ATSC 3.0 translator, using either an ATSC 3.0 or ATSC 1.0 input signal.

TRedess updated me on its exciter and transmitter, which are capable of simultaneously transmitting ATSC 3.0 and 5G Broadcast signals in a manner compliant with ATSC 3.0 standards. Castanet also showed ATSC 3.0 and 5G Broadcast in the ATSC booth (see story, page 17). The system uses time-division multiplexing and ATSC 3.0’s bootstrap to identify segments with ATSC 3.0 and 5G Broadcast content.

The demonstration used all but 10% of the channel capacity for 5G Broadcast. TRedess showed me an application that calculated data capacity and bandwidth for different ratios of ATSC 3.0 and 5G Broadcast time.

As I’ve written before, I have not seen any 5G Broadcast phones, dongles or receivers for sale to the public in the U.S. As with ATSC 3.0, the success of 5G Broadcast in the U.S. will depend on the availability and cost of receivers.

The flexibility of the ATSC 3.0 standard, which allows for interleaving with other standards like 3GPP, presents new possibilities for broadcasters. In my next column, I’ll review sessions covering these opportunities and what broadcasters will have to do to take advantage of them. I’ll also have a short report on the National Translator Association (NTA) conference in Reno.

As always, comments and questions are welcome. Email me at dlung@transmitter.com.

In the past, I’ve often used my New Year’s column to summarize the state of broadcasting and highlight last year’s developments and I what I expect to happen this year. I don’t have much to add to what I wrote in my 2025 columns covering the NAB Show, ATSC yearly meeting, and, recently, the FCC’s Fifth Further Notice of Proposed Rulemaking on NextGen TV.

In 2026, I’ll be looking to see if the transition to ATSC 3.0 accelerates. Whether it does, and at what rate, will depend on more viewers with antennas buying TV sets that have ATSC 3.0 capability. That will require more low-cost TVs and adapters. Will enough manufacturers make the effort to obtain the licenses and certifications required for sets to work with content-protected programming?

This month, I’ll share some of the free software I use to understand how TV signals make it from the transmitter to the receive antenna, both in numbers and maps. If you want to see how changing an antenna or transmitter location impacts coverage, these tools will help.

The two main tools are TVStudy, which has been significantly updated since I last wrote about it in TV Tech, and QGIS, a program that allows you to drag and drop shapefiles from TVStudy, Census.gov, or other sites for display on a map.

FCC’s TVStudy
In the past, you would have to spend thousands of dollars to get the software and databases needed to calculate a station’s terrain-limited, interference-free coverage. Today, you can download the FCC’s TVStudy for free, along with terrain and population databases and detailed technical data on every TV station in the U.S, for coverage and interference analysis.

TVStudy for MacOS and Linux is available for download here. A complete download is more than 10 GB in size—that’s large but workable with an internet connection of 50 Mbps or better. Download the manuals and follow the installation guide precisely. The documentation is excellent.

Most of the issues I’ve seen are with MySQL—TVStudy requires MySQL 5.7 or 8.0, and many Linux distributions install MariaDB by default. For Debian-based distributions like Ubuntu and Kubuntu, simply replace MariaDB with MySQL 8.0 before trying to install TVStudy. TVStudy requires Java 8. Most operating systems now default to later versions, so it may be necessary to install Java 8. Look for OpenJDK Runtime Environment build 1.8.0. Use it to open the TVStudy program.

TVStudy will download the latest TV and FM License and Management System (LMS) databases. With them, you can search for stations and study coverage and interference. This is important, as most online terrain-sensitive coverage maps do not show the impact of interference.

TVStudy 2.3.0 can create KMZ files that can be opened in Google Earth to see coverage and interference at a specific location. View the TVStudy KMZ file I’ve uploaded here. I’ve also displayed the undesired sources’ location and call signs on the map (Fig. 1).

If you are interested in learning more about TVStudy and how to use it, let me know and I’ll provide more details and tips by email or in future columns.

QGIS
QGIS is another program I currently use. Most Linux distributions have it available in their repositories. Versions are also available for MacOS and Windows. There are many QGIS tutorials online, but some are based on outdated versions or are targeted at people developing their own complicated maps, which isn’t necessary when just dragging and dropping existing shapefiles into the program. If you get frustrated with a tutorial, try another one. A well-worded question often brings a good response on Google search.

Most of the map issues I’ve seen come from using the wrong coordinate system. The spreadsheet output from TVStudy has west longitude as a positive number. If dropped into QGIS unmodified, it will end up on the other side of the Earth. When working with shapefiles, QGIS usually handles the coordinates correctly and makes the necessary conversions. Learning about coordinate systems and mapping on the web and QGIS helps answer questions like, “Why is my nondirectional contour an oval on my map?”

Spend some time getting comfortable with basic maps, then drag and drop the contours.shp and coverpts.shp files from a TVStudy study’s shapefile folder onto the map. You can use colors to display the “DSIGNAL” field strength on the map. Setting up styles can be complicated so to help you get started. I’ve uploaded some files you can use to get familiar with it here.

The map shown here (Fig. 2) was created with QGIS and some of the sample files I posted. TVStudy pulled all the data for the WDMR-LD study from the LMS files downloaded in the program. I’ve shown the areas with interference in red.

If you just want to see the areas with coverage or within a certain field strength range, that’s easy to do in QGIS. You can download my files and experiment with QGIS before doing your own studies with TVStudy. I used a 1-kilometer cell size for the example, but TVStudy allows the use of smaller cells for higher resolution.

Additional shapefiles are available here. For specific map items, search for “tigerline shapefiles” for additional U.S. shapefiles.” I’ve found maps online for Mexican roads and urban areas, as well as world oceans and U.S. water bodies. Note that some areas will be polygons, which QGIS may display with a filled-in color. That can be changed by selecting “Simple Line” in the “Symbology” section in the layer’s properties if needed.

QGIS isn’t limited to displaying geographic and TVStudy data. If data is available as a .csv file with coordinates, it can be displayed. Potential applications include mapping towers, microwave paths, etc., once the data is in .csv format. The “Processing Toolbox” allows counting the population covered in a TVStudy coverpts.shp file by county or ZIP code, for example, and outputting the data into a .csv file for analysis. I’m still finding new things I can do with it!

When I write about antennas, readers respond with questions on specific antennas or ask how the antennas I’ve described work (I still get email messages asking about the Gray-Hoverman and UHF rhombic antennas I wrote about two decades ago!). This month, I’ll review some antenna basics that will help you evaluate any antenna, although I doubt any readers are fooled by antenna ads claiming over 100-mile reception. Measurements are great, but an understanding of how antenna elements work will help to evaluate designs just by looking at them!

Size is important, but the correct size for the TV-frequency band is most important. The simplest antenna is a half-wave dipole, and when looking at any antenna—transmit or receive—you should see dimensions close to a half-wavelength at the lowest frequency of interest.

Table 1 (next page) shows the free-space half-wavelength at the upper and lower edges of the VHF and UHF TV bands. The element’s actual half-wavelength will be affected by surrounding elements. In a band, the antenna’s active element, the one connected to the coax or balun, should be close to half a wavelength. Combination VHF/UHF antennas will have multiple active elements to cover different bands.

Impedance match for receive antennas isn’t nearly as critical as it is for transmitting antennas, but it will impact signal level, particularly with a long cable between the antenna and the amplifier or tuner. Notice the difference in wavelength in each band. Ideally, the antenna will provide a reasonable impedance match across the TV channels. In addition to size, this is an area in which a look at the antenna can provide some clues.

Shape Matters, Too
At UHF frequencies, a fan dipole, like those seen on bow-tie antennas, will work over a wide frequency range. Decades ago, I made a test antenna to evaluate radiated TV third harmonics using a fan dipole made from copper-clad PC board. While a solid element is best, broadband TV antennas typically use a wire bow-tie or something similar. Larger diameter or thicker elements have a wider bandwidth than thin rods. New designs will have UHF active elements optimized for the post-repack UHF band from 470 to 608 MHz.

Elements with different lengths can be connected to increase bandwidth. Log-periodic antennas do this and offer excellent bandwidth. The “Silver Sensor” indoor antenna, popular when DTV broadcasting started, is one example. You’ll sometimes see multiple dipoles connected to improve VHF performance in an antenna. Note that in these cases I’m talking about active antenna elements—ones connected to the coax or matching network, not the directors or reflectors in front of them.

What about those directors and reflectors? A perfect reflector behind the active elements should double the signal into the element. For a TV antenna covering the entire UHF band, a single rod reflector isn’t going to be as effective as a screen with multiple rods or a wire grid.

Directors—the elements in front of the active element—act as a lens to focus more signal into it. Many directors can be added in front of the active element to improve gain, but as gain increases, bandwidth decreases. For TV antennas, this makes it difficult to obtain significant gain over the entire UHF band with a large number of directors.

The gain of an antenna is directly related to its directivity or beamwidth. When evaluating antennas, do not include gain from amplifiers. A high-gain antenna will require more careful aiming and could be a problem if the TV stations to be received are not in the same location. Gain can be achieved by reducing the azimuth (side-to-side) or elevation beamwidth (up-to-down) directivity. Receive antennas will reduce both to achieve higher gain. Most gain in high-power TV transmitting antennas comes from a narrow elevation beamwidth.

Let’s use some antennas to illustrate these points.

Real-World Examples
An example of an antenna that depends on the reflector for gain is the Scala Paraflector. These are used at frequencies from 450 MHz to over 900 MHz for both reception and transmission. The PR-TV operates in the UHF TV band and has over 16 dB gain at channel 36. It’s a simple antenna, with only two elements in front of the reflector and a very narrow beamwidth. It also has a narrow bandwidth so the desired frequency needs to be specified when ordering the antenna.

Channel Master claims a gain of 12 decibels for its 8-bay “EXTREMEtenna 80” bow-tie antenna. This number appears to be the sum of 9 dB from the 8 active elements and 3 dB from the reflector. The basic design is simple (broadband elements and a reflector) so performance shouldn’t vary much over the UHF TV band.

A low-cost TV antenna that’s widely available is the RCA ANT705E and, at less than $50, it performed impressively. As you can see from the image, it has a curved reflector and a wider active element shaped like two horseshoes to cover the UHF band. There are only two directors.

Using our size criteria, the only element that will be significant at VHF is the large folded dipole in front of the reflector. The UHF active element may help a bit as a VHF director, VHF but I doubt the reflector will have much impact. I no longer have my Los Angeles apartment for testing antennas over a wide range of channels, so I was unable to evaluate VHF performance.

The Televes Ellipse Mix is an excellent antenna that costs significantly more but worked well in a difficult environment (see slide 24 in the PDF here). It has a broadband UHF active element. Like the Paraflector and the RCA antenna, there is also a shaped UHF reflector. Unlike the RCA, Televes added a reflector for VHF at the back of the antenna. Rather than use a long boom with director elements in a row, Televes has three levels of directors arranged to focus energy from the upper and lower directors into the UHF active element.

The active UHF elements on both the RCA and Televes antennas don’t taper to a point at the center like traditional bow-tie antenna elements. Elements no longer have to work up to channel 69 (806 MHz), so having more area at the lower channels improves performance.

What about indoor antennas? The flat antennas made with copper film on a plastic sheet are easier to stick in a window than the ANT705E. I did some limited testing comparing the Walmart Onn Indoor High-Quality Clear HDTV Antenna with the RCA ANT1120E and Best Buy “Essentials Ultra-Thin” antennas. As expected, the larger RCA antenna provided the strongest signal and the smaller one from Best Buy was the weakest. At UHF channel 36, the difference wasn’t huge. The Onn antenna, at under $25, is the cheapest and the one I’ve been using while traveling.

Typically after an NAB Show, I’d be writing about new transmitter innovations, new antenna designs and new RF test equipment. This year, I didn’t find many. Existing products saw some improvements, but nothing like I saw at past shows, as transmission technology evolved from klystrons to IOTs to solid-state amplifiers, which in turn evolved to LDMOS transistors and Doherty amplifiers. DTV modulators evolved from card frames filled with circuit boards to a few chips taking up less than a postcard’s space on a circuit board.

While I didn’t see many new products, I did see existing products and software that had been improved to better support ATSC 3.0 and make conversion to ATSC 3.0 easier.

UDP Over IP Issues
Stations and station groups have started relying on internet connections and cloud-based encoding, and converting these distribution platforms will be more complicated. Fortunately, the ATSC STLTP (Studio-to-Transmitter Link Transport Protocol) standard works great for point-to-point distribution, but use of User Datagram Protocol (UDP) over the internet can cause problems.

With ATSC 1.0, if an ASI or UDP packet is lost, the viewer may experience a brief freeze in the picture or a short audio interruption. With ATSC 3.0, if an STLTP UDP packet is lost and STLTP’s forward error correction can’t fix it, transmitters today will kill the RF, which can take several seconds to return to full power when the next good packet is received.

Packet loss and latency variations on internet links require the use of additional protocols such as SRT and RIST. Papers in Broadcast Engineering and IT (BEIT) sessions from One Media Technologies and Amazon Web Services (AWS) described cloud-native ATSC 3.0 distribution systems.

See the AWS presentation “ATSC 3.0 and TV 3.0 in the Cloud,” available in the BEIT Proceedings, for an excellent description of the problems encountered in delivering reliable ATSC 3.0/TV 3.0 STLTP streams over the internet and how they were solved.

It was encouraging to see more real-world ATSC 3.0 issues being discussed at the show—we may not have much time to work out the bugs before ATSC 1.0 is shut down! There was a wide range of applications and devices on display in the ATSC booth in the West Hall, but there remains a long way to go until all TV receivers have ATSC 3.0 capability.

I was happy to see that MediaProxy—which uses the Silicon Dust HDHomerun tuner—was able to get A3SA approval for decrypting ATSC 3.0 content in its server. Ideally, other professional equipment vendors, such as
Airwavz, will be able to add decryption to their software. Handling decryption in an approved app or web browser should make it easier for device manufacturers such as Silicon Dust or GTMedia to support decryption.

5G Broadcast Makes Gains
Like year, 5G Broadcast equipment was on display with OMB and Televes showing 5G Broadcast systems. At the Televes booth, I saw a demo using phones from
One Plus and Samsung with the
Qualcomm chip. I’ve written about 5G Broadcast in the past, and while it has been shown that it is inferior to ATSC 3.0 in efficiency and coverage, proponents argue it will be easier to include in smartphones.

An OMB rep said they were finding interest in 5G Broadcast from Eastern European countries and in smaller countries where smartphones were the primary device for watching video and broadcast TV was still analog.

There was also discussion of improvements to 5G Broadcast, which is based on LTE technology, to incorporate some of the tools, such as interleaving, that make ATSC 3.0 more robust in upcoming 3GPP releases.

Before NAB Show, HC2 Broadcasting requested permission from the FCC to use 5G Broadcast on its LPTV stations. “SuperFrank” Copsidas recently received a construction permit to move his LPTV in San Diego from VHF to a UHF channel. Considering Qualcomm’s location in San Diego, I would expect him to request approval to use 5G Broadcast on that station after the move.

We will likely see more 5G Broadcasts on the air before next year’s NAB Show. The question, of course, is how many phones will be able to receive it and when will they be available? I’m using a $59 ATSC 3.0 USB tuner from eBay with my Samsung S24 now. While not yet available in the U.S., One Media has shown dongles and phones with ATSC 3.0 reception for a few years now.

New NextGen TV Tuner Tested
Back to my ATSC 3.0 phone: It is the GTMedia HDTV Mate ATSC 3.0 USB tuner (check Amazon, eBay and Aliexpress; price and availability may have changed since tariffs were imposed; I currently see unit prices from $40-$70). I had good results with it at the NAB Show and was able to pick up the Black Mountain ATSC 3.0 transmission in both the West Hall Food Court and behind the ATSC booth in the West Hall.

The device worked fine on my Samsung S24; the tuner was able to receive both ATSC 3.0 stations in Washington, D.C., WIAV-CD and WHUT-TV. The device uses the Sony tuner/demodulator chip; ATSC 1.0 performance is excellent. The HDTV Player app is the best Android tuner app I’ve seen, allowing tuning directly to a specific channel. Signal level in dBm and SNR in dB are displayed numerically and on bar graphs.

At present, the app only works on Android devices. It does not support content protection, although after tuning to a protected stream it displays a message indicating “DRM channels will work with a further version on DRM-certificated devices.”

In my next column, I’ll return to a popular topic—TV receive antennas. Like many of you, I often get asked to recommend an antenna. However, instead of focusing on specific antenna makes and models, I’ll show you how to use physics to evaluate a receive antenna not by its miles of coverage, but by its looks.

As always, your comments and questions are welcome! Email me at
dlung@transmitter.com.

NAB’s February petition to the FCC to shut off ATSC 1.0 in the top 55 markets less than three years from now focused increased attention on ATSC 3.0 at the 2025 NAB Show. I found no lack of products for broadcasters looking to switch to ATSC 3.0 and, as others and I have shown in articles on previous NAB Shows, there are now several low-cost options for encoding and transmitting ATSC 3.0 signals.

However, until enough viewers have ATSC 3.0-compatible TVs and the commission relaxes rules requiring stations to continue broadcasting on ATSC 1.0 shared channels, any ATSC 1.0 shutdown will be difficult. What broadcasters have been looking for since starting ATSC 3.0 broadcasts is a “killer app” that will drive the transition to NextGen TV.

At NAB Show, I got the impression that “killer app” is the Broadcast Positioning System. It provides precise timing—and with a sufficient number of stations—accurate positioning. The FCC’s notice of inquiry on “Promoting the Development of Positioning, Navigation, and Timing [PNT] Technologies and Solutions” (WT-Docket 25-110) outlines the need for an alternative PNT system.

Secure System
BPS is an alternative PNT system using ATSC 3.0 stations. One advantage of BPS is that it is very resistant to jamming or spoofing (substituting valid data with inaccurate data) due to the high power, large number and wide frequency range of TV transmitters (VHF and UHF). A nationwide BPS depends on nationwide ATSC 3.0 coverage. If the government wants BPS, broadcasters hope it will encourage the government to provide regulatory and perhaps financial support for the ATSC 3.0 transition needed for BPS.

Is BPS a good enough alternative? In Denver, the National Institute of Standards and Technology (NIST), TV station KWGN and the NAB worked together to test BPS reliability and accuracy. The results were presented in “Field Test of ATSC 3.0/BPS Precise Time Distribution” at the Broadcast Engineering and IT Conference at the NAB Show by Jeff Sherman, supervisory physicist at NIST.

The test found that BPS time was within plus or minus 10 nanoseconds of the UTC (NIST) standard time, except for a sudden time shift of approximately -25 nanoseconds, which the presentation said “is likely related to known operator maintenance activity that involved lower transmitter power and/or a possible change to undetermined interference in the NLOS [non-line-of-sight] propagation of KWGN to NIST Boulder.”

The paper, available in the NAB 2025 BEIT Conference Proceedings, includes details on testing and comparisons to GPS accuracy, with the results of the tests showing BPS comparable to GPS L1 band. Additional information is available in the paper “Time Transfer Performance of the Broadcast Positioning System.”

How difficult is it to deploy BPS? For a BPS station to provide accurate time, it requires its own traceable time standard. These are expensive, but two alternatives were covered at the show.

Follow the ‘Leader’
One option uses a station with a traceable time standard as a “leader” other stations, or “followers,” can use as a reference. A test setup, using stations WHUT in Washington, D.C., (the “leader”) and WNUV Baltimore (the “follower”), showed how this works. Details on the system and its configuration were provided in “BPS Mesh Network Initial Deployment Report,” a BEIT presentation by Mark Corl, senior vice president, emergent technology, Triveni Digital.

The other time reference, demonstrated in an NAB PILOT exhibit with Sinclair’s ATSC 3.0 station KVCW, used an eLORAN station as the reference. The NAB’s comments in FCC WT Docket No. 25-110 pointed out that BPS could be part of a “system of systems.” The eLORAN demonstration is an example of one system providing a reference for BPS; BPS could also provide a reference for other timing systems, such as the networking Precision Time Protocol (PTP).

For BPS to be a reliable backup for GPS, many more stations will have to transmit it. Monitoring will be required to ensure BPS stations are transmitting accurate time. A station transmitting BPS data will need to add a robust PLP (QPSK with 2/15 coding) to carry the broadcast time information. Less than 10 kbps is required, so the impact on total channel capacity is minimal.

Additional equipment is required to add the time data and adjust the timing of the transmitted signal. Avateq outlined a basic BPS configuration at Rohde & Schwarz’s tech talk at NAB Show. “BPS Network Application Diagram” from this presentation shows the components in a leader­follower BPS configuration. At this time, Avateq and Triveni are the only suppliers of BPS-compatible equipment, and only two transmitter companies—GatesAir and Rohde & Schwarz—have exciters that work with BPS. I talked with other gateway and transmitter vendors at NAB Show and got the impression that if a market develops for BPS products, they will support it.

During the session Q&A, the cost to add BPS to a station was quoted as “about $200,000.” That wasn’t broken down, but I expect the traceable time reference or stable holdover reference is a large part of this.

Keeping Track of Time Is Crucial
Will BPS work with a single frequency network of transmitters (SFN) or with translators? BPS depends not only on precise time transmission, but transmission of the precise location of the BPS station. That’s necessary to account for how long it takes the time transmitted from the station to reach the BPS receiver. A 6-meter error in distance will result in an error of approximately 20 nanoseconds.

Obviously, timing could be a problem if the original BPS station’s time is transmitted on multiple stations in an SFN or via translators. The good news is the ATSC 3.0 standard allows for each transmitter in an SFN to have its own identifier that specifies its location. Each translator or transmitter with BPS in an SFN will require a traceable reference time source. SFNs today rely on GPS for synchronizing transmission frequency and time, but if BPS is to be a backup for GPS, another reference will be needed. Since the BPS data will be transmitted in a very robust PLP, signals from other BPS stations should be available as a reference.

The added complexity for SFNs and translators needs to be considered when calculating the cost to broadcasters for implementing BPS. While having BPS on translators would provide coverage in remote areas, in the end it may be simpler to strip BPS data from the translator’s signal, especially if robust streams from distant full-power stations are receivable in those areas.

Receivers will have to identify individual transmitters on the same channel, whether transmitters in an SFN or other co-channel stations. With a BPS PLP signal-to-noise ratio of -5 dB, there will be locations where two or more stations’ coverage overlaps, so this will be important. When multiple transmitters are received on the same channel, Avateq’s receiver uses the signal that arrives first for the time reference.

Please share your comments at dlung@transmitter.com.

I’m sure any remaining technical issues will be resolved and, if there is government and broadcaster support for BPS, equipment will be available from multiple vendors.

We’re seeing increasing interest in data transmission as a potential revenue source (a “broadcast CDN”). Where does BPS fit in? Can broadcasters charge BPS users for the service? During one of the NAB sessions on BPS, it was estimated that loss of GPS for a period of 90 days would result in costs of over $1 billion per day. Will power companies, financial institutions and other critical users that depend on a precision time reference, including the government, be willing to pay broadcasters to transmit BPS as insurance against GPS loss?

Can we count on individual broadcasters to successfully deploy BPS? Larger station groups have the resources to do this, but some sort of a prepackaged solution that can be installed, maintained and remotely monitored at smaller stations will be necessary. Engineers have done a great job developing the technology that enables BPS. Let’s hope the government and business lets us take advantage of it.

In my next column, I’ll cover other topics from the 2025 NAB Show as well as some testing I did with a $59 (as this was written) USB ATSC 3.0 receiver that can plug into an Android phone while in Las Vegas. As always, your comments are welcome!

While going through items I’d saved from my former apartment in Los Angeles, I came across a copy of “TV Technology” with my first article, dated November 1984. It included my user report on the Abekas 52 digital-effects unit I’d selected for KSCI, where I was working at the time. Looking through that issue, the articles and the ads showed how much broadcast technology has changed and how some things remain the same.

The photo below shows the front page of that issue. A full-resolution view, with readable text, is available here.

One thing that hasn’t changed in 40 years is the demand for spectrum. The article “TV, Land Mobile Vie for UHF” was about the Federal Communications Commission giving the Los Angeles Sheriff’s Department the use of Channel 19. As I was the chief engineer at KSCI, which was on Channel 18, I was concerned about that. As a consequence, not only was this issue the one with my first article, I was also quoted in the spectrum article: “ ‘We are very concerned about it,’ said Doug Lung, CE at KSCI TV/Channel 18 San Bernardino, CA. ‘How are they defining ‘undue’ interference?’ ”

I added that when Channel 19 was used by the Los Angeles Olympic Coordinating Committee during the 1984 Summer Olympics, I noticed intermittent herring-bone interference on a high-quality demodulator and mild interference on a Sony receiver.

Other articles in that issue that may bring back memories include the front-page article “MTS Use Surveyed,” on stations’ stereo TV plans, and a guest editorial by George E. DeVault Jr. (president and general manager of WKPT-TV and then-chairman of the NAB’s UHF Committee) titled “UHFers Fight for True Parity.”

The comments are interesting in that they point to issues with cable carriage of UHF stations and competition from out-of-market “superstations.” DeVault Jr. was also concerned that the presence of LPTV stations would limit full-power stations’ ability to improve existing service through the use of translators.

I recall that UHF TV stations didn’t get as much respect as the established VHF stations back then. Since the DTV transition, broadcasters have found UHF works better given the poor performance of indoor VHF antennas and the huge amount of noise in the VHF band coming from motors, switching power supplies, solar inverters, LED lights and other electric devices.

Greg Best’s article, “Improve Specs for MTS Xmtr,” described how to optimize analog-TV transmitter performance for stereo and how to test stereo performance. Hans Schmid’s article, “Nonlinear Waveform Distortion,” explained the different types of distortion that can occur when processing or transmitting analog video.

There were no ads for TV transmitters in that issue! However, Modulation Sciences had a two-page spread describing its TV-stereo generator. “Broadcast Engineering” had a much smaller ad with its TV-stereo generator.

Computer Revolution
Looking back at the changes over the last four decades, two things stand out as contributors to the transformation in TV broadcasting—computers, including digital processing, and connectivity.

That Abekas 52 had circuit boards filled with ICs, including the large TRW A/D converter I mentioned in the article. Comparing that chip with today’s technology, it was bigger than a 2 TB SSD or a complete Raspberry Pi Pico Zero 2W computer. The Abekas 52 and other digital video-processing gear did amazing things in 1984 but finding a defective IC, bad capacitor or bad solder joint when these units started acting weird could be difficult.

Today, there is no need to convert analog to digital and back again in production. What used to take racks of equipment, patch bays and waveform monitors to maintain can be done on a few local servers or in the cloud. A hardware user interface is still required, but it likely has a generic processor under the hood.

Reporters upload content to the cloud over the internet and editors and the production crew at the station can edit it in the cloud and ship it to master control, which increasingly is also operating in the cloud. From there it can go to the transmitter or final microwave link to the transmitter, wherever it is located.

I don’t recall seeing any digital components handling RF in transmitters or microwaves 40 years ago. Transmitter exciters had a large chassis filled with tunable inductors, variable capacitors and over a dozen potentiometers, in addition to transistors and crystal-controlled oscillators.

Fortunately, the inductors and capacitors didn’t require much if any routine adjustment, but the corrections for differential gain and phase and other distortions often had to be adjusted as the transmitter tube aged or was replaced. There were no high-power solid-state TV transmitters 40 years ago.

Today, an entire digital TV exciter can fit on a circuit board the size of a sheet of paper. With perhaps one or two one-time settings, all adjustments and corrections are done in software, many automatically. A large FPGA chip generates the waveforms and handles the corrections. There is even code available to create an ATSC 3.0 transmitter using an off-the-shelf SDR, as I wrote about in my January 2023 article, “Learning About ATSC 3.0—on the Web or on the Bench.”

The other big change is connectivity. Forty years ago, content distribution had largely moved from terrestrial telco circuits and shipped (“bicycled”) video tapes to satellite. As fiber connections became more affordable, distribution moved from the sky back to the ground.

Today, content is increasingly delivered over the Internet, using protocols like SRT and RIST. The cost has dropped to the point where internet connectivity can replace microwave links, assuming the reduction in reliablity is acceptable. For remote sites, space is an option, using Starlink. As other low-latency, low-earth-orbit satellite constellations are launched, the cost of these connections is likely to drop. An important caveat is satellite Internet bandwidth is likely to remain limited, so this option may not be available in densely populated areas.

In 1984, I couldn’t have imagined the technology TV production and broadcasting is using today. I don’t expect to be around 40 years from now, but I expect broadcasting will change more in the next 40 years than it has in the last 40.

ATSC 3.0 allows broadcasting to merge with internet distribution platforms through virtual channels. At some point in the future, the user may not realize if the program they are watching is coming from a broadcast tower or the internet.

What’s Next?
Of course, 40 years from now, will we still be using the internet to deliver video and audio or will it look as out-of-date as AOL, CompuServe and dial-up connections do now?

One thing that hasn’t changed in 40 years is TV stations still require a transmitter with sufficient power and an antenna at sufficient height to reach viewers. Forty years from now, will broadcasters still need their own transmitter and antenna?

I’m interested in hearing what those of you who do expect to be around 40 years from now expect TV broadcasting to look like in 40 years! Email me at dlung@transmitter.com.

Stations wanting to convert to ATSC 3.0 have had trouble finding an ATSC 1.0 home for their high-definition (HD) and standard-definition (SD) streams. Using MPEG-4 (AVC) for ATSC 1.0 has been tried but created problems for viewers with older TV sets or old “coupon” converter boxes. I’ll suggest some options that might work, if the FCC allows it.

Finding Space for Homeless ATSC 1.0 Program Streams
There is much support for ATSC 3.0, including recent interest from the U.S. government, which is studying the standard’s Broadcast Positioning System utility as a backup for GPS. New features are being added, including standards based (DRM) radio. Work has started on developing ways for 3.0 to work with 3GPP wireless technology.

While LG is no longer selling ATSC 3.0 TV sets, other manufacturers such as Sony, Samsug, Hisense and now TCL are offering them, and consumers now have a variety of inexpensive set-top box receivers to choose from. Features like virtual channels (delivered by internet to the TV rather than over-the-air) and broadcaster applications that provide additional content and the ability to restart programs (using the internet) will make 3.0 even more attractive to viewers.

However, spectrum and data bandwidth for ATSC 3.0 are limited. Converting existing stations to 3.0 requires finding a home for their ATSC 1.0 programs on the stations remaining on 1.0. The popularity of ATSC 1.0 “diginets” has made it difficult to find a space for a new 3.0 host’s streams. One obvious solution is to improve the efficiency of the existing ATSC 1.0 capacity by using MPEG-4 video, which has roughly twice the efficiency of MPEG-2.

By The Numbers
Table 1 shows an example of average bandwidth allocation for a station carrying two HD streams and four SD streams in their 19.392 Mbps ATSC 1.0 stream. The HD streams are assumed to have a primary 5.1 audio and a secondary stereo audio stream for audio description or second language.

Extra bandwidth is allowed for null packets and PSIP data. Quality will vary depending on program content and use of aggressive statistical multiplexing is required to give an HD stream more bandwidth when needed and let the SD streams have more bandwidth when the HD streams don’t need it.

Early tests used MPEG-4 (AVC) encoding on one or more SD streams. Table 2 shows the result of converting all the SD streams in Table 1 to MPEG-4, keeping the same audio bit rates and reducing the video bit rate to 650 kbps.

That allows equal or greater video quality than a 1,000 kbps MPEG-2 stream. This configuration provides an extra 1,400 kbps of bandwidth, which could be used for one more MPEG-4 SD streams. Reducing the MPEG-4 SD bit rate to 50% of the MPEG-4 bit rate would allow two additional MPEG-4 SD streams at the lower rate.

Unfortunately, attempts to use MPEG-4 have resulted in complaints that the program had audio but no video from viewers with older TVs or NTIA coupon set-top boxes. If there was a way to hide the MPEG-4 content from the older TVs, it would likely eliminate the complaints, but I haven’t found a way to do that. As a result, use of MPEG-4 by full power stations has been limited.

There is a way to add significantly more capacity to lighthouse stations without leaving any viewers behind—transmit the HD content in MPEG-4 with a simulcast in SD in MPEG-2—leave all existing SD diginets in MPEG-2. Viewers with older TVs would not lose any programs, but the main program would be in SD on those sets. This would not matter for anyone using the NTIA coupon set-top boxes as their output is SD only.

Table 3 shows the bandwidth allocation for MPEG-4 only HD and MPEG-2 SD, assuming a 50% reduction in bandwidth for the HD streams compared to MPEG-2. Audio is 5.1 for the MPEG-4 HD streams and stereo for the SD MPEG streams, with room for a stereo secondary audio on the SD simulcasts. This scenario provides over 3,600 kbps of extra bandwidth, enough for three more MPEG-2 SD streams with stereo audio.

Simulcast Issues
If you’re interested in this approach, take some time to build a spreadsheet and test other scenarios. Consider dropping one of the MPEG-2 SD diginets—that would provide enough bandwidth for another MPEG-4 HD and its companion MPEG-2 SD. Another option would be to use stereo audio on the MPEG-4 HDs and a 96-kbps mono secondary audio tracks. With a small reduction in video bandwidth that would also allow an additional HD and companion SD.

Encoder experts may notice a potential problem with the simulcast approach. Statistical multiplexing allocates bandwidth based on stream content and priority. If two streams are airing complex content requiring extra bandwidth at the same time it may limit the bandwidth available to other streams. However, if the HD and SD companion streams can share the same audio (5.1 main and stereo secondary) the bandwidth gained could offset that effect and perhaps work better than delaying the video one of the streams.

The FCC has made it clear they want no viewers left behind. Allowing conversion of HD streams to MPEG-4 while providing an SD stream (with secondary audio and audio description) to viewers with older sets is one way to accomplish that goal. It will require approval from the FCC and likely negotiations with cable companies, if the SD MPEG-2 stream alone remains the “primary stream.”

Ideally, the FCC would consider both streams, MPEG-2 and MPEG-4, if both were identical, as “primary” for regulatory purposes.

Updates
I’ve received emails from readers interested in building the Pi-OTA DTV monitor I described in my November 2023 column at I’ve put all the files and instructions on how to build it on Github at https://github.com/DougLung2000/OTA-Pi-Monitor .

Since publishing the article I’ve made the web server more robust by adding the gunicorn WSGI and modifying the way the displayed data is updated. I also have tested it on the Raspberry Pi 5.

Long time readers will recall that “Kaffeine” was my favorite application for viewing and recording DTV broadcasts on my Linux laptop. Linux distributions are moving from X.org to the Wayland desktop server and Kaffeine does not work under Wayland.

Now I use “w_scan” (available in most Linux distributions) to scan for available channels wherever I happen to be and save them as a VLC “xspf” playlist file. An improved version, “w_scan2”, is available at https://github.com/stefantalpalaru/w_scan2. You can edit the source code to stop it from scanning UHF channels above 36. Load the xspf file into VLC to view the programs and program guides.

VLC allows recording, but I found it easier to install “tvheadend”, also available in most Linux distributions, for recording. It runs in the background as a systemd process and thus I don’t miss as many recordings as I did with Kaffeine.

As always, your comments and questions are welcome. Email me at dlung@transmitter.com.

I attended several sessions at the 2024 NAB Broadcast Engineering and IT Conference (BEIT). Many of the presentations were about signals modulating the RF, focusing on ATSC 3.0 and ATSC 3.0 applications rather than the generation and transmission of RF. 

We’ve seen ATSC 3.0 can do more than provide video and audio to TV sets. As I’ve said before, the transition to ATSC 3.0 depends on the availability of devices to receive ATSC 3.0. Demand for these ancillary services could provide an incentive for broadcasters to switch to ATSC 3.0 and for devices to include ATSC 3.0 capability. 

Precision Navigation and Timing
One service that is receiving attention is precision navigation and timing—PNT—and how broadcast transmission can support it.

Judah Levine, NIST Fellow, Time and Frequency Division, National Institute of Standards and Technology showed how unmodified broadcast TV signals could be used to provide precision time and frequency in “Transmitting Time and Frequency Data by Using Broadcast TV Signals Observed in Common-View.” 

In the Common-View system, the transmitter is not modified but the receive time of a known pattern in the signal (i.e. bootstrap in ATSC 3.0) is compared with a local clock at two or more receivers to determine the transmitted time and frequency of the signal. Propagation delay and multipath will introduce some errors but the error can be calculated. 

The method is similar to one used in the early days of color TV when the 3.579 MHz color subcarrier frequency of network affiliates was locked to that of the network. This technique stopped working when broadcasters started using digital frame synchronizers and with their own local reference. 

There were several presentations on the Broadcast Positioning Service (BPS). The presentations reiterated the need for a backup for GPS and outlined the progress being made in developing and testing BPS in different locations. BPS is one of the systems for GPS backup under consideration. Comments from experts at the sessions indicated BPS was at or near the top of the list. 

One presentation, “ATSC 3.0 Broadcast Positioning System (BPS) Mesh Network” by Vladimir Anishchenko, president and CTO at Avateq, and Mark Corl, senior vice president, Emergent Technology Development at Triveni Digital, showed how multiple transmitters could form a mesh network, with “leader” transmitters having traceable time references and “followers” that would compare their clocks with those from neighboring transmitters, including the leader transmitters. The paper in the NAB BEIT Proceedings has detailed drawings and tables showing how this works. Fig. 1 shows a simplified diagram from a Humber College presentation.

Emergency Alerting & 5G
The BEIT presentation “ATSC 3.0 and Wireless Emergency Alerting – A Great Match” by Fred Engel at PBS North Carolina and Chris Lamb at Device Solutions showed how ATSC 3.0 can provide alerts when the cellular system is down, as was the case during the Maui fires. It is easier to protect a high-power, high-tower transmission site than cell sites distributed in the area experiencing the disaster. 

The other advantage, which utilizes the paging receivers developed by Device Solutions, is reduced latency. Conventional paging systems using digital radios employed by public safety agencies can have minutes of delay compared to seconds with systems using ATSC 3.0. This video shows how ATSC 3.0 is used to deliver emergency dispatch information over a large area. 

While there was interest in 5G Broadcast transmission and there were products on display to transmit 5G Broadcast, I heard more discussions about how ATSC 3.0 and 5G (both 5G Broadcast and New Radio) could complement each other. I did not see any papers devoted to 5G Broadcast, but there were presentations showing how 5G (both 5G Broadcast and 5G New Radio) and ATSC 3.0 could work together. 

In her presentation “How IP-based Broadcast Meets 5G for Resilient and Sustainable Media Distribution,” Emily Dubs, head of technology at the DVB Project, explained how the DVB-I standard works with existing broadcast standards, not only DVB-T2 but ATSC 3.0 and others, to give devices multiple options for receiving content via broadcast if available and if not, ways to obtain the content over an IP connection (wired or wireless). 

The DVB-I service discovery can show receivers the optimum path for receiving program content. As part of the explanation, Dubs also discussed the challenges broadcasters face getting their content to mobile devices and how broadcasters and mobile network operators can help each other with distribution. More information is available in the presentation and at https://dvb-i.tv/.

Mapping 5G Frames into ATSC 3.0
One of the most interesting technical presentations was from Louis Libin and Mike Simon from ONE Media Technologies showing how 5G frames could be mapped into ATSC 3.0 signals to allow a broadcaster to deliver data in both an ATSC 3.0 format and a 5G compatible format and take advantage of receive device power saving options available in both. 

Even though the ATSC 3.0 standard is extremely flexible, there are differences with 3GPP 5G standards that make it difficult to add time-multiplexed 3GPP 5G frames. Libin and Simon explained how an extension to the ATSC 3.0 standard and update to 5G New Radio (perhaps in 3GPP Release 20) could allow a station to transmit a signal with portions available on both ATSC 3.0 receivers and 5G devices.  

The presentation, “The Convergence Opportunity for ATSC 3.0 and 5G NR Multicast Broadcast Service” is available in the Proceedings and with a password (available from ONE Media) at https://onemediallc.com/libinsimon/. 

I did catch a presentation that focused on transmitting RF, “An Innovative In-Service Antenna Monitoring System to Protect Your Antenna and Transmission Line” by Heidi Stamm, Anton Lindner, Christoph Neumaier and Todd Loney from Spinner. The system uses the DTV signal from the transmitter and directional couplers to analyze reflections in the transmission line and antenna system. The paper shows how the distance to fault (or degradation) is calculated and some examples of how it works, including detecting a problem inside a slot antenna. 

The NAB BEIT proceedings are available for purchase ($100) and download at https://nabpilot.org/beitc-proceedings/. 

I made a presentation to the Public Media Venture TechConnect 24, held on Friday before the NAB BEIT. Billed as the “Master Class with Doug Lung: Analyzing TV Coverage – ATSC 1.0, ATSC 3.0 and 5G Broadcast,” I covered the different methods for calculating coverage, some of the software available for calculating coverage and how techniques used for calculating ATSC 1.0 coverage can be modified for calculating ATSC 3.0 and 5G Broadcast coverage. 

The presentation showed how different propagation models and different transmission systems performed under different circumstances. It also includes an extensive reference section with links for further study. The presentation is available at https://www.transmitter.com/tc2024/ 

As always, your comments and questions are welcome. Email me at dlung@transmitter.com. 

This month I’ll focus on what I saw on the exhibit floor at NAB Show. This isn’t a comprehensive overview of all the RF and transmission exhibits and show news—other articles in TV Tech do that well. Instead, I’ll be looking at a few exhibits I found interesting. Next month I’ll discuss other RF technology topics from the show, including BPS and 5G Broadcast.

Rohde & Schwarz
Many broadcasters purchased Rohde & Schwarz THU-9 transmitters during and after the repack, so I wasn’t surprised that Rohde’s unveiling of its new UHF TV transmitter, the TE1, attracted a large crowd Monday afternoon despite its location in the South Hall, far away from other transmitter and distribution exhibits.

Some of the changes are apparent looking at the transmitter. Unlike the THU9, which was designed for worldwide use, the TE1 was designed specifically for the U.S. market where higher power transmitters are required. The exciters mount horizontally in the rack, allowing up to 14 amplifiers per cabinet and increasing the per-cabinet output power to 24.5 kW. Looking at the back of the transmitter, you can see the changes in the combiner output and load. 

Also, the power input is now at the top of the cabinet, cleaning up the wiring on the right side (from the rear) power distribution panel. (The colorful LED cabinet lighting in the photo is not available as an option.) 

The exciter includes the ATSC 3.0 modulator—a separate SDE-900 unit is not required. Reflecting the TE1 North American market focus, the specifications show ATSC and ATSC 3.0 as the only supported standards. The product brochure says it is “Prepared for 5G Broadcast.” 

End-to-End ATSC 3.0 Transmission System
Anywave showed a complete ATSC 3.0 signal chain that will make it easy for broadcasters, particularly LPTVs, to switch to ATSC 3.0. It includes the encoder, gateway and scheduler, and exciter. 

A key feature of the gateway/scheduler is a custom design using FPGAs rather than software running on a server. This enables a complete ATSC 3.0 encoder, gateway/scheduler and exciter in three rack units of space to consume a fraction of the power required for a server-based system. 

Their AW9200 Exciter+ can be configured for use as a translator for ATSC 3.0 with a gateway option that allows modification of signaling at the translator site without additional gateways.

Smart Dummy Load
As transmitters become more efficient, engineers are taking a closer look at the power consumed by dummy loads in systems with multiple transmitter cabinets. When one of the cabinets shuts down, the combiner becomes unbalanced. 

In a two-cabinet system, this results in half the remaining power going into a reject load. This doesn’t happen that often, so any power used to cool the dummy load while both cabinets are operating normally is wasted. 

Dielectric’s solution is the “OptiLoad,” which turns on the cooling pumps only when required. This is more complicated than it sounds. If the reject load fails, it will shut down the entire transmitter. Worse, if it fails to shut down the transmitter and a cabinet fails, the coolant pressure and steam generated by the load can cause a mess before the reflected power takes down the transmitter. The OptiLoad includes RF sensors and other features designed to prevent such disasters. 

Simplifying ATSC 3.0 Station Configuration
Most ATSC 3.0 stations set their modulation and coding and PLP configura-tions once and don’t change them. Triveni showed its “Station Manager,” which makes setting, storing and restoring ATSC 3.0 configurations easier. 

Anyone who has looked at the ATSC 3.0 standard knows there are an almost infinite number of configurations available. Changing one parameter can require changing another parameter to maintain a legal ATSC 3.0 stream. The Station Manager interface makes this easier. 

I can also see how Station Manager could become an important part of the broadcast core network, which will allow broadcasters to offer excess data capacity for other uses, such is IoT. This will likely require participating broadcasters to change their transmission parameters to accommodate demand for data delivery with different bandwidth and robustness requirements. 

Broadcast Positioning Service Solution
Many engineers see the ATSC 3.0 Broadcast Positioning Service (BPS) as a key driver of ATSC 3.0 support from the government and perhaps device manufacturers as well. I’ve discussed BPS before and will have more on it next month, but wanted to highlight one product that will make it easier for broadcasters to add BPS capability to their transmission systems. Stations that want to transmit BPS signals will need to precisely time the transmission of the ATSC 3.0 bootstrap. 

The Avateq AVQ-1050 consists of a BPS receiver and a BPS synchronizer, which together compare the received signal with a reference clock and adjust the transmission time to make it a stable, precise time source. It can directly control the transmission time from a Rohde & Schwarz exciter without connection to the gateway and scheduler, which may not be located at the transmitter site. 

ATSC 3.0 for Legacy Cable Systems
As the transition to ATSC 3.0 progresses, there will be a need for cable companies to receive ATSC 3.0 signals. While the ideal scenario would be for the cable companies to deliver a stream that enables most of the ATSC 3.0 features, during the transition, they will need to convert the ATSC 3.0 to a form that will work with their existing set-top boxes. 

To that end, the Sencore TXS3800 ATSC 3.0 to ATSC 1.0 transcoder can provide decryption and transcode video and audio from ATSC 3.0 to ATSC 1.0 formats in an ATSC 1.0 transport stream. 

NextGen-Compliant Dongles
I was happy to see several low-cost set-top box devices displayed in the ATSC booth that support A3SA content protection. However, I’m still looking for an ATSC 3.0 NextGen-compliant tuner I can plug into a USB port of my laptop to view ATSC 3.0 protected content on the road.

Dongles have been available for a few years, but none made it to the consumer market and none I’ve found support A3SA content protection. It doesn’t appear that will happen soon, but after seeing compliant set-top boxes based on Android TV, perhaps it will be possible to create an ATSC 3.0 dongle that will work with Widevine-enabled Android tablets. ATSC 3.0 has many advantages when it comes to mobility so I expect there would be demand for portable ATSC 3.0 receivers, especially in areas prone to hurricanes and other natural disasters. l

As always, your comments and questions are welcome. Email me at dlung@transmitter.com. 

While 5G is, and has been for several years, a household word, a technology that this fifth-generation of personal wireless communication has spawned may be new to many: “5G Broadcast” (or “LTE-based 5G Terrestrial Broadcast” as it’s officially referenced).

5G Broadcast is based on the use of wireless broadband network technology for distribution of media to consumers on mobile devices. However, this version of 5G is not based on the current one-to-one (unicast) distribution for streaming, but rather a one-to-many (broadcast) dissemination scheme using the “high-tower/high-power” approach that conventional broadcasters rely on.

Another big difference is that 5G Broadcast primarily targets mobile devices, instead of TVs as the current ATSC 3.0 transmission does. 5G Broadcast and conventional broadcast do have something in common though: use of UHF TV broadcast spectrum. 

Learn More
Although the jury is still out as to the ultimate future of 5G Broadcast, it behooves broadcasters to learn about it, as it could be a gamechanger in the broadcast industry. 

“5G has promised to revolutionize the mobile telecommunications world, offering unprecedented speed, capacity and reliability,” says Sam Matheny, NAB CTO. “5G Broadcast technology is a subset aimed at enhancing live streaming mobile TV services.”

The NAB Show, April 14-17 in Las Vegas, will feature opportunities for an up close and personal look at 5G Broadcast, beginning with a demonstration of the technology in a special booth where “5G Broadcast is spoken.”

Frank Copsidas, the CEO of XGen Network, an advocacy organization for 5G Broadcast will be in the West Hall (W3849) promoting  5G Broadcast. “We’ll be showing new exciters and transmitter equipment, as well as receivers,” he said. “And we will have a demo on the floor for directly receiving 5G Broadcast transmissions.”

XGen Network launched the first U.S. experimental 5G broadcast operation in 2023 at Boston DMA WWOO-LD, operating on TV Ch. 28, and has applied for two additional 5G Broadcast experimental licenses in Connecticut.

One of the big advantages of 5G Broadcast—aside from offloading content with high viewership levels from the conventional cellular “one-to-one” infrastructure—is that it operates on a direct-to-mobile basis, Copsidas said. “The beauty of 5G Broadcast is that it goes from a standard broadcast tower straight to a user’s smartphone,” said Copsidas. “There’s no SIM card, Wi-Fi, or Bluetooth needed.”  

And while one-to-many dissemination of entertainment programming is definitely part of the grand plan for 5G Broadcast, Copsidas says that’s not the main focus right now. 

“Our number one priority in the U.S. for 5G Broadcast is first responder and emergency alerts,” he said. “We can put out emergency alerts in the 17 languages that the FCC wants within one-half second. We do plan to show some solutions for first responders at NAB. We can put out streams of data (directed to first responders) to smartphones; all you need is an app on the phone. 

“Qualcomm, which is one of our partners, has also developed a CPE [customer premises equipment] box for 5G Broadcast, which we’ll have at the show,” he added. “Qualcomm has been a phenomenal partner. They keep coming up with 5G Broadcast ideas for us and we keep coming up with ideas for them.”

Although there are yet no commercially-marketed products (smartphones) specifically designed for receiving 5G Broadcasts, Copsidas says this is not really a problem.

“I can buy a phone directly from the OnePlus 11 internet website,” said Copsidas. “When we get it here, we have Qualcomm software that can access the phone’s chip and open up our frequency. There are 5G, satellite and 5G Broadcast, along with other services in that chip, and they are all independent of one another.”

In addition to the demos and exhibits, the LPTV Broadcasters Association’s annual meeting during the show (Rm. W1202 in the West Hall, April 14), will include a 5G Broadcast monetization session.

Industry Experts Weigh In
While no one knows for certain where 5G Broadcast’s footprint will land in the broadcasting ecosphere, it could augment ATSC 3.0 broadcasting to reach both big screen TVs in the home and handheld mobile devices. 

Jordi Giménez, head of technology at the 5G Media Action Group (5G-MAG), an international non-profit group established to encourage collaboration in connection with mobile media services, strongly encourages broadcasters to learn as much as possible about the new transmission modality.

“I believe it is time to pay more attention to the technology from the service and application point of view,” said Giménez. “5G Broadcast is a 3GPP technology, meant to operate in the mainstream device market, and aligned with streaming workflows. 

“With the blooming of streaming apps for video/TV and audio/radio, it is time to play with them,” Giménez added. “Broadcast works; it has worked for a century. But this time service providers and operators have the opportunity to embed it in streaming applications with a protocol stack aligned with the internet and with a technology that works in the 3GPP ecosystem of devices, operating systems and apps.

“Support for 5G Broadcast has grown significantly over the last few years, and our historic accomplishment further exemplifies the broad interest and growth,” said Lorenzo Casaccia, vice president of technical standards and IP at Qualcomm Technologies. “The collaboration between Ateme, WWOO-LD, and Qualcomm Technologies is a major step forward in how content can be delivered to a wide array of devices.”

Doug Lung, vice president of Broadcast Technology for NBCUniversal Local and long-time writer of TV Tech's RF Technology column, also advises attendees to use the NAB Show to learn more about 5G, especially as it could augment the NextGen TV standard that’s being deployed. 

(Read: What is 5G Broadcast?)

“Transmission of ATSC 3.0 and 5G Broadcast on a single channel was demonstrated last year,” said Lung. “But practical implementation will depend on modification of one or both standards. At the NAB Show we may have a better idea of whether this ‘dual transmission’ will ever be practical.”

Lung said that in making the rounds at this year’s NAB Show he’ll be looking to see what’s out there in the way of 5G Broadcast receivers, and what 3GPP standard they support, “even if they are protypes.” 

Knowledge is Power
With the support of proponents such as XGen, 5G Broadcast could well become the favored way of delivering content to the masses, especially to those wanting to consume it on mobile devices. Only time will tell.

One thing is certain, however, if 5G Broadcast does wind up in a dominant position, those primed with as much knowledge about it as possible will definitely have the ball in their court. As expressed by the English philosopher Francis Bacon more than 400 years ago, “knowledge is power,” and you’ll want to be in the front row if and when 5G Broadcast takes center stage, and there’s no better place right now to learn about the new standard than the NAB Show.

“For broadcasters, understanding the nuances of the various facets of 5G technology and how they will integrate into current infrastructures is vital,” said the NAB’s Matheny. “The 2024 NAB Show (will serve) as an essential gathering place for industry leaders to delve into 5G broadcast's innovations, challenges and the potential opportunities it presents for augmenting content delivery and viewer experiences." 

With the support of proponents such as Qualcomm and XGEN, 5G Broadcast could well become the favored way of delivering content to the masses, especially to those wanting to consume it on mobile devices. Only time will tell.

One thing is certain however—if 5G Broadcast does wind up in a dominant position, those primed with as much knowledge about it as possible will definitely have the ball in their court. 

“For broadcasters, understanding the nuances of the various facets of 5G technology and how they will integrate into current infrastructures is vital,” said Matheny. “The 2024 NAB Show (will serve) as an essential gathering place for industry leaders to delve into 5G broadcast’s innovations, challenges and the potential opportunities it presents for augmenting content delivery and viewer experiences.” 

To register for the NAB Show, visit nabshow.com/2024/

As we start a new year, I thought it would be interesting to look back at 2023 and offer some comments on what I expect lies ahead for 2024 and beyond.  

A Quiet 2023
After the activity surrounding the FCC incentive auction channel repack and the post-repack antenna and transmitter upgrades, the past year was quiet when it came to spectrum issues. The RF spectrum scene, however, is changing.  

When the FCC lifted its freeze on channel changes, many TV stations, (31 at last count), filed channel change petitions to move from VHF channels to UHF TV channels. While VHF channels can work well to cover large areas if viewers are using outdoor antennas, reception of VHF with indoor antennas has been problematic for reasons I’ve discussed before. As of Nov. 24, 2023, 481 stations were still transmitting on VHF channels, 51 of them on low-VHF Channels 2–6. 

After rushing to get red and blue C-band interference filters installed on satellite dishes, wireless operators started using the 3.7 GHz to 3.98 GHz band that used to be devoted to C-band satellite down-links. From what I’ve seen, there have only been a few problems with interference­—which may be due to program distribution moving from satellite to terrestrial distribution via fiber and even the internet. 

As the year ended, broadcasters faced a Nov. 29 deadline to certify that their microwave links in the 12.7 GHz band were operating as licensed; file an application to modify the license to correct any errors or omissions; or cancel the license. The FCC is looking to allocate this spectrum for wireless broadband use, but it isn’t clear exactly how this will be used. One possibility is fixed wireless internet.

Transition to NextGen TV
The slow rollout of ATSC 3.0 continued in 2023. Available spectrum to allow simultaneous transmission of primary programming in both 3.0 and 1.0 is still a problem, although stations continue to learn how to trade capacity to make it work. One potential solution is to move from MPEG-2 to AVC (MPEG-4) encoding, but incompatibility with older TV sets has frustrated that effort (viewers hear the audio but get a black screen from MPEG-4 on older TVs). 

More stations switched on content protection in 2023. While this caused few problems for large-screen ATSC 3.0 TV sets, viewers with early set-top boxes like SiliconDust’s HDHomerun lost reception of protected channels. 

Fortunately, as the year ended, set-top boxes that support content protection became available—the ZapperBox and the ADTH box, for example. Except for ATSC 1.0, almost all video delivery today is content protected, whether streamed or over fiber or cable TV. The challenge for the ATSC 3.0 roll out will be making that content protection as easy for viewers and device manufacturers as it is for cable and streaming services.  

Unfortunately, LG, a major supplier of ATSC 3.0 TV sets, has stopped selling sets with ATSC 3.0 tuners after losing a patent battle with Constellation Designs over non-uniform constellations. 

Fig. 1 shows a non-uniform 64-QAM constellation generated by my software-defined ATSC 3.0 transmitter. Non-uniform constellations are more efficient than the uniform (rectangular) constellations used in other digital TV COFDM systems. 

Constellation’s patent would appear to apply to equipment that generates ATSC 3.0 RF signals as well as receivers. Readers may remember that similar patent battles erupted during the rollout of the original ATSC (1.0) DTV and affected both receiver and transmitter manufacturers. In the end it had very little impact on the rollout of DTV in the United States. I don’t expect it to be a major issue for ATSC 3.0. 

For more information on non-uniform constellations, see the complaint filed by Constellation Designs LLC at https://drive.google.com/file/d/1I5-nhg3MMcR8peqIEei8XVM5kNpwVHOc/view 

Non-TV uses of ATSC 3.0 received more attention. The Broadcast Position Standard (BPS) that would provide a backup for GPS, which many services depend on for accurate timing was tested, as well as radio over ATSC 3.0. I covered both topics in detail in my 2023 NAB Show coverage in TV Tech. 

I’m often asked, “When will broadcasters complete the transition to ATSC 3.0?” My usual answer is I don’t see it happening for at least 5-7 years. The key factor will be the widespread availability of ATSC 3.0 tuners in TV sets, set-top boxes or other devices.

It's usually followed up by “What can broadcasters do to speed the adoption of ATSC 3.0?” Almost all 3.0 programming is a duplicate of what stations are airing in ATSC 1.0. Better encoding and the addition of HDR provide a better picture, but is that enough? Broadcast applications and “virtual channels” delivered over the internet are attractive, but support varies among devices.  

While the focus has been on the benefits that ATSC 3.0 provides consumers, don’t ignore the benefit it provides broadcasters. More bandwidth (about 20% more for similar coverage) and encoding that’s 4x more efficient is equivalent to getting additional ATSC 1.0 channels! It gets better—a broadcaster can use LDM to add a very robust signal for mobile TV, data or other applications like radio with little impact on the main channel coverage. 

Perhaps rather than relying on consumer pull, we need a stronger broadcaster push. This push could be funding an ATSC 3.0 set-top box program, either by building and distributing converters or providing discount coupons. 

Financial incentives for device manufacturers (not only TV sets but streaming devices and set-top boxes) to include ATSC 3.0 capability, just as streaming services do now, could drive adoption. Since smart TVs know what the consumer is watching, offering manufacturers a bonus when the set tunes to an ATSC 3.0 service would help ensure over-the-TV wasn’t buried deep in the menus. 

We’ve seen stations move away from using two-way radio systems and microwave ENG systems in favor of cell phones and bonded cellular. Will the same transition happen to broadcasting? 

We can’t ignore the possibility that TV “broadcasting” will eventually move to the internet and 5G wireless. I don’t see this happening in the next five years, but if the ATSC 3.0 transition fails and as transmitters bought during the repack need replacement, the idea of relying on internet delivery, perhaps supplemented with 5G broadcast, might look attractive, especially if it allows broadcasters to avoid the regulatory burdens associated with an FCC license. More likely, we’ll see multiple broadcast platforms, with over-the-air continuing to exist in some form. 

Viewers are discovering free over-the-air TV to avoid the cost of cable TV and streaming subscriptions. Antenna sales are strong. For broadcasters to take full advantage of this trend, we need to push the transition to ATSC 3.0 technology to be able to both complement and compete with other platforms like internet streaming (wired and wireless) and 5G broadcast for both viewers and content.

IEEE BTS Returns
Finally, I was happy to see that IEEE Broadcast Technology Symposium was back in 2023. The last Symposium was in 2019 and I wondered if it would return after the 2022 Symposium was canceled. 

Thanks to the efforts of Jim Stenberg, Paul Shulins and the presenters and volunteers supporting it, the symposium was a success, with approximately 90 people attending the two-day session at NAB headquarters in Washington, D.C. Visit https://bts.ieee.org/ for more information on the IEEE Broadcast Technology Society. I’ll be covering the 2023 Symposium’s papers in a future column. 

As always, your questions and comments are welcome. Email me at dlung@transmitter.com.

WASHINGTON—After a four-year pandemic-driven hiatus, the IEEE Broadcast Technology Society’s Fall Symposium—a forum for the exchange of information about the latest developments in broadcasting technology—has re-emerged, with little indication that there had been an interruption in what has been a fall tradition since the 1950s. The Nov. 14-15 event, by the NAB at their new headquarters building, attracted nearly 90 engineers, equipment manufacturers and academics from 10 states and six foreign nations, with some travelling from as far away as Italy, Switzerland, and Argentina. 

Sessions covered a wide range of topics focused on the latest in content delivery technologies, as well as problems and issues challenging today’s broadcasters. While some subject matter—such as keeping a broadcast facility safe from hackers—was common to both sides of the aisle, television was definitely out in front in terms of the number of presentations, with more than half being TV-specific. And while ATSC 3.0 was a big topic of discussion, it was not the exclusive focus.

The Tale of Télé-Québec
Guy Bouchard, a broadcast consultant formerly in charge of the digital delivery infrastructure at Canadian broadcaster, Télé-Québec, addressed an issue created by the FCC’s reapportioning of C-band satellite spectrum used by broadcasters.

In February 2020, the FCC adopted new rules for the 3.7 to 4.2 GHz C-Band that allocated the lower 280 MHz of that band for terrestrial wireless use. This forced existing satellite operators to repack their operations into the upper 200 MHz of the band, from 4.0 to 4.2 GHz, according to Bouchard, who noted that this forced move created an operational problem for some broadcasters, including Télé-Québec, a public TV network in Montreal with a government-funded educational mandate to air all programming in French. 

Télé-Québec is available on cable, over-the-air, and now via OTT, covering 96% of the Quebec population and Bouchard said that although only about 7% of its viewers receive Télé-Québec via antennas, that audience was important. “That number is very stable; it hasn’t shrunk (and) we wanted to keep those who grew up watching us,” he said.

To serve the OTA audience, Télé-Québec uses 18 transmitter sites, all connected to the broadcast center by C-Band satellite, with two-thirds of those transmitters in remote locations without access to fiber or high-speed internet connectivity. All of the sites were equipped with 4.5-meter satellite antennas and that these had proved adequate until the C-Band repack. 

“The sites receive their feeds from Galaxy 19,” he said, adding that while Télé-Québec services shared a transponder with another user, the reduced power density had not really been a factor in delivering reliable signals to the OTA transmitters.

“We had a four to six dB link margin, which was acceptable under most conditions,” said Bouchard.

Télé-Québec’s studio-to-transmitter problems arose when the sharing of C-Band spectrum with 5G terrestrial wireless carriers began.

“Sharing bandwidth with a cellphone company is a bit like sharing a banana with a gorilla,” he observed, stating that to minimize interference from nearby wireless devices on adjacent frequencies, heavy filtering had to be added to satellite dish LNBs (low-noise block downconverters), and these filters considerably reduced the link margin.

“Ordinarily, there’s no real filtering at the input of an LNB,” said Bouchard. “That’s why you can get a really low noise figure,” he added, noting that while the 12-pole band-stop filters that were installed ahead of the LNBs were very effective in blocking 5G interference, they reduced the LNB gain by about a dB.

“This lowered the effective aperture of the satellite antenna,” he said.

While the performance reduction could be tolerated under most conditions, a wet snowfall was now the death knell when it came to delivering programming to the transmitter sites.

“Sticky snow is the worst factor affecting low-margin C-Band service,” he said. “It distorts the shape of the receive dish, lowering its gain and causes outages lasting anywhere from 20 minutes to an hour.” Bouchard said that while dish deicers worked, they could be overwhelmed by heavy snowfalls.

“While they reduced the duration of outages, the deicers didn’t eliminate them.”

SRT to the Rescue
Bouchard said that while the obvious solution would be to increase satellite delivery link margins by installing larger dishes, this was not a particularly viable option.

“We had 18 transmitter sites to consider,” he said. “And based on the relatively small audience served, the large expense associated with installing larger dishes would be difficult to justify.”

Bouchard said that after some investigation, Télé-Québec opted to try out a fairly new technology—secure reliable transport or “SRT”—as a more cost-effective solution. He explained that SRT, which combines low-latency streaming with advanced technology to handle missing packets to ensure data transmission quality and continuity of service, seemed ideal for delivering programming over the marginal internet delivery paths that existed at the majority of its transmitter sites.

“With SRT, the payload is sent via UDP (user datagram protocol) and flow control packets are sent via TCP (transmission control protocol),” he explained. “A flow control feature permits the use of error detection and provides retransmission of missing packets.”

Bouchard reported that in a trial implementation at Télé-Québec, SRT had proven to be very reliable as an alternative for delivering programming to transmitter sites. 

“We did have questions about how well it would perform, but after the initial trial no artifacts were reported and no alarms were received” he said, noting that reliability was proven even over the poorly performing Internet paths at some of the transmitter sites.

“Our solution to the reduced link margin issue was to continue to send programming via C-Band satellite, but to back this up with an SRT-encoded compressed feed going via the public Internet,” said Bouchard, explaining that the main delivery path continues to be via satellite, but when the dish signal becomes unstable, the transmitter feeds failback to the Internet-delivered video and audio.

He said that while more testing is needed, it seems that the SRT-encoded feeds are for now a viable alternative to retrofitting transmitter sites with larger satellite dishes.

Asked about whether he thought that Télé-Québec might eventually discontinue satellite linkage to their transmitter sites, Bouchard said that while this was not a consideration at present, given the success of the SRT-implemented delivery so far, it might be something to consider. 

“For now, SRT transmission is a viable option to improve low-margin satellite site reliability.”

Other television-related presentations at the symposium included the addition of DRM (Digital Radio Mondiale) digital radio service to ATSC 3.0 television transmissions, methodologies for flash-cutting to NextGen TV delivery, seamless insertion of ads in streamed video, ATSC 3.0’s datacasting potential, considerations in retrofitting or replacing of transmission systems, and determining the impact of adjacent channel interference in ATSC 3.0 transmissions.   

Special Recognition
A special feature of all BTS Symposiums is the recognition of an individual who has made significant contributions in the industry, with the presentation of the Jules Cohen Award for Outstanding Broadcast Engineering. 

The 2023 recipient was H. Douglas (Doug) Lung, vice president of Broadcast technology for NBC Universal Local, and also a long-time TV Tech columnist. The award is based on an engineer’s integrity and professionalism, along with the quality and thoughtfulness of his or her work, and was established in 2015.

This is Lung's second industry recognition received this year; at the NAB Show, he received the NAB TV Engineering Excellence Award.  

Long-time readers know I like to experiment with remote monitoring projects. A few decades ago, I described my “Cheap Remote” based on a Blue Earth Microcomputer, as an inexpensive device about the same size as today’s Raspberry Pi and other single board computers. I needed the money I’d budgeted for a commercial remote control to cover the cost of an air conditioner for the shelter for a translator I was installing in Midland, Texas. 

Lately I’ve been looking for an inexpensive way to monitor a remote transmitter over a limited bandwidth internet connection. 

The result is the OTA (Over-the-Air) Pi Monitor. Using an Orange Pi 4 LTS and a Hauppauge WinTV-dualHD Dual USB tuner, the whole setup, with case and power supply, can be put together for less than $200. It requires about 2 Mbps of upload bandwidth (adjustable) when viewing the video clips. 

Hardware
Fig. 1 shows part of the web page available after connecting to the device. There is a real-time display of signal level, SNR and a continuity count (10-minute interval). Video is available for the main HD program and the SD programs. A short segment is recorded at the top and bottom of each hour. 

I designed the box to work without high-speed internet. HD video is transcoded from MPEG-2 to AVC (MPEG-4) at quarter resolution (960x540) and frame rate is reduced to 15 fps. SD video is also converted to AVC at 15 fps. The peak bitrate for playback of the downconverted HD stream is under 2 Mbps and around 1 Mbps for the SD streams. The video plays in a web browser. Below the video is transport data with PID data and bit rates (not visible on the screenshot). 

The OTA Pi Monitor should also work with a Raspberry Pi 4, Orange Pi 5B or other single-board computer running a Linux operating system. The Orange Pi 4 LTS I used has 16 GB eMMC storage and 4 GB of RAM. Whether using an Orange Pi or other SBC, be sure the power supply can deliver enough current; otherwise, as I learned the hard way, the computer will crash when transcoding the video. 

Program Flow
The OTA Pi Monitor programs are simple. As you can see from Fig. 2, it isn’t fancy! Operation is simple: A one-line script, sigdata2.sh, uses dvbv5-zap to grab the tuner data and provide the signal level, SNR and continuity error count. A small Python program, sigdata.py (only 3,905 bytes), runs that script every second to obtain the readings for the web page. A Flask module in the sigdata.py program provides a web server using a small index.html template. Flask’s socketio module receives the data from sigdata2.sh. A 656-byte javascript app, signalapp.js, displays the real-time data on the web page. 

I wasn’t able to find a way to easily stream live video over an internet connection, so I decided instead to use dvbv5-zap, the same program used to obtain the data from the tuner, to do a 60-second transport stream capture every 30 minutes. The system timer, available on most Linux distributions, sets the recording times. 

Once recorded, FFmpeg is used to extract program streams from the transport stream and transcode them for lower bit-rate playback. Finally, the tsanalyzer program from TSDuck is run to analyze the transport stream and generate a text file. All of this is done in the 15-line (including comments) tscapproc.sh script. The Flask web server displays the transport stream analysis text file and provides HTML5 links to the transcoded program streams (video and audio).

There isn’t room to include program listings in this column but I’m happy to share them; email me and I’ll send you the latest version. If there is enough interest, I’ll make them available for download. 

The most complicated part of this project was getting all the pieces working together. Google searches helped and eventually I was able to assemble a working program. I’d been working on this project for a few years and I found when I tried to use my original software as a starting point it failed due to slightly different syntax in the updated libraries. When stuff fails, the error messages are not always clear, but copying the error message to Google and doing a search often provides a solution.

Program Component Details
Here are some more details on the software components in the OTA Pi Monitor.

Flask simplifies creating a website with real-time data and video. There are several tutorials online. The trickiest part was getting Flask SocketIO working with signalapp.js (delivered by the Pi) and socket.io.min.js (downloaded from cloudflare.com by the browser) to display the real-time data to the screen. I’m happy to share the solution I came up with.

The DVBv5-tools provide an easy way to interface with PCIe or USB DTV tuners. The OTA Pi Monitor relies on the dvbv5-zap tool. Most Linux distributions offer dvbv5-zap but the package name may vary. I found the best way to record the transport stream was to tune the signal with dvbv5-zap in the record mode, which sends the transport stream to a software DVR device, which can be dumped into a file using the “cat” command. 

The dvbv5-zap program works well with the Hauppauge WinTV-dualHD tuner. Because the dualHD has two tuners, it is possible to do transport stream captures without stopping the signal quality readings. 

TSDuck is a very powerful toolkit that can analyze and edit transport streams among other things. I’m using it as a text-based version of TSReader (learn more about it and download versions for most operating systems, including Windows, macOS, and common Linux distributions, including Ubuntu, Fedora, Debian and the Raspberry Pi OS at https://tsduck.io/). 

I had to compile the program from source for use on the Orange Pi 4 LTS, but the build instructions on the TSDuck web page made that easy.

Transcoding is done with FFmpeg. All it takes is one command line to extract a program’s video and audio from a transport stream and output a file with different resolution (if needed), frame rate, and video and audio codecs at different bit rates and quality. I had trouble extracting specific program streams until I found the “-map p:#” command line option where “#” is the program ID number. That option will transcode the video as well as all audio streams under that program ID. 

I hope you find this useful for monitoring remote translator sites or perhaps even as a simple way to check on your station when you don’t have access to a TV or antenna or are traveling out of the coverage area. I’m happy to share the files I used to create the OTA Pi Monitor and look forward to hearing from readers who’ve built one and improved it! I continue to update it as time permits and as noted, am happy to share the files and help you build one. 

As always, your questions and comments are welcome. Email me at dlung@transmitter.com.

Part I

This month I conclude my coverage of the centennial NAB Show with a look at the impact of content protection on ATSC 3.0 test equipment, transmission system innovations, the disappearance of RFS, and compatible MIMO for ATSC 3.0.

ATSC 3.0 Equipment and Content Protection
Broadcasters introducing ATSC 3.0 content protection noticed their test gear stopped displaying audio and video. The good news at the NAB Show was that Sencore is working with A3SA, the ATSC 3.0 security authority, and will add the ability to decrypt protected signals to their ARD3000 series ATSC 3.0 receiver/decoders. Triveni will also support display of content protected video and audio in its ATSC 3.0 Streamscope XM products. 

At its booth in the West Hall, Tolka showed its new ATSC 3.0 set-top box and dongle being sold by ADTH with support for content protection. It wasn’t clear if the dongle would work on a laptop, but with the right application it should work on Android devices using the Stagefright media playback engine that supports Widevine L1. 

The ADTH set-top box uses Android and is the NextGen TV-certified to support ATSC 3.0 with content protection o the U.S. market. Widevine is also supported in the Chrome and Firefox browsers. I haven’t seen any ATSC 3.0 devices using browsers to display protected content and wouldn’t expect to until there is more support for Dolby AC-4 audio. 

Airwavz is working on support for content protection on its Redzone ATSC 3.0 tuner and associated TVXplorer software but was not ready to say when it would be available. 

Last year I reported on the Promax ATSC 3.0 and ATSC 1.0 analyzer and 6 GHz spectrum analyzer. The “Atlas” is now available for $10,800 and was on display at the show. While there are less expensive options for ATSC 3.0 signal analysis, the unit’s spectrum analyzer capability and features could be useful in some applications. I was able to use the spectrum analyzer in the unit on display to find one of the ATSC 3.0 signals in the West Hall and tune to it to see what it contained. Content protection was not available but video and audio demodulation isn’t the main use of this unit.  

Transmission Innovations
Although I spent little time with transmitters, Anywave’s “all-in-one” DTV exciter caught my attention. It can generate ATSC 1.0 or 3.0 signals and seems ideal for broadcasters looking for a simple way to deploy ATSC 3.0. The exciter is available with ATSC 3.0 gateway as well as GPS reference options. It pairs with Anywave’s new ATSC 3.0 H265 route encoder. It was hard to believe Anywave had squeezed that much capability into a one rack unit enclosure.

At mountain-top transmission sites and where interference is an issue, optimizing coverage can require different beam tilt in different directions. One way to achieve this is through an array of panel antennas. However, as Dielectric’s John Schadler described in his paper “Broadcast Travelling Wave Antenna with Azimuthal Beam Tilt,” Dielectric’s solution using four pylon cylinders, each of which can be designed with different amounts of electric beam tilt, allows a much simpler feed system. 

This antenna would be ideal for locations like Farnsworth Peak in Utah where less tilt is needed north and south to cover Ogden and Provo and more tilt is needed to reach the populations in metro Salt Lake City to the east and Tooele to the west. The white paper provides more detail than was what was presented at the Dielectric NAB breakfast and is available at www.dielectric.com/technical-resources/.

Dielectric demonstrated its Apollo monitoring service for RFHAWKEYE, which provides an in-service TDR (time domain reflectometry) sweep of a station’s antenna and transmission line. Resolution is sufficient to see individual line flanges. While the RFHAWKEYE has been available for a few years, the new Apollo service remotely monitors a station’s antenna and transmission line for small changes and is capable of alerting the station. 

I saw an example of this in Los Angeles on Mount Wilson after heavy snow and ice bent a rigid transmission line but did not break it. Dielectric’s remote monitoring detected the small change and the location of the change and alerted the station so that the snow and ice could be removed from the line. Because the RF sweep takes place in the high-VHF TV band I was concerned it wouldn’t work in a high RF environment like the Los Angeles Mount Wilson site where there is a full power station on every high-VHF channel except 8 and 10. So far that hasn’t been a problem. 

What Happened to RFS?
One name familiar to TV transmitter engineers was absent from this year’s show, RFS which announced that it would shut down its broadcast division at the end of 2022 and put its intellectual property up for sale. As of the show, no one had purchased it. Fortunately RFS developed a very good step-by-step procedure for tuning its filters and engineers who have learned the procedure are available to re-tune filters if needed. Most of the full UHF power stations in New York are transmitting on an RFS antenna fed from an RFS combiner at One World Trade Center. Fortunately the filters are rugged passive devices that will likely outlast the transmitters. 

When I asked some of the companies I thought might be interested in the RFS IP why they hadn’t purchased it, I was asked how many high-power filters and combiners I expected to buy in the next few years. The repack and subsequent upgrade of non-repacked stations in the last five years has resulted in most stations being set for the next decade or so, which means far fewer sales of high-power equipment. Low- and medium-power sales may increase if the ATSC 3.0 roll out leads to more construction of distributed transmission systems to increase coverage and data capacity. 

RFS also made microwave dishes, semi-rigid coaxial cable and waveguide at its plant in Meriden, Conn. The cable manufacturing business was sold to Amphenol, which sells the products under the RFS Technologies name. Alive Telecom bought some of the dish manufacturing equipment, but not the intellectual property, and is now selling microwave dishes as well as broadcast antennas. 

ETRI's DEMO of ATSC 3.0
One item that I did not mention in my previous article was ETRI’s demonstration of compatible ATSC 3.0 MIMO. Last year they showed a system using dual polarized transmit and receive antennas that was capable of delivering data rates near 100 Mbps. However, it could not deliver content to non-MIMO receivers. This year, ETRI in cooperation with KBS, Cleverlogic, and Televes showed how LDM could be used to provide a low data-rate, very robust signal in addition to the high data-rate MIMO enhanced layer. 

The parameters demonstrated would only provide enough capacity for one 720p program stream, 1.3 Mbps, in the non-MIMO core layer but it was using QPSK and a 2/15 code rate which resulted in a less than 0 dB signal-to-noise ratio (SNR) threshold.  A robust layer with less error correction would allow more program streams. The MIMO enhanced layer required an SNR of 30 dB and provided 64.7 Mbps data capacity. 

Broadcasters and engineers are still discovering what’s possible with the ATSC 3.0 standard. Look for more on the technology and products in future columns. 

Interest in over-the-air reception of TV in the U.S. continues to grow as evidenced by sales of antennas, with CTA estimating that the total antenna marketplace in the U.S. will exceed 53 million homes by 2025. While the ATSC 3.0 build out continues, a new concept, “5G Broadcast” is now being considered as another option for high-power, high-tower “next generation” TV broadcasting. 

There is already one experimental 5G Broadcast station on the air (WWOO-LD in Westmoreland, NH, announced in July), and broadcasters in other parts of the world are testing 5G Broadcast deployment. 

Will it replace ATSC 3.0 as the “next generation” broadcast technology? The major factor, in my opinion, will be whether or not consumers and broadcasters drop over-the-air TV in favor of streaming programming over the internet. 

5G Broadcast is targeted primarily at mobile devices, where data capacity for video distribution is still a concern. Consumer adoption of ATSC 3.0, so far, has been limited to fixed TV sets. While more people are cutting the cord and discovering (or rediscovering) over the air broadcasts, far more of these sets are connected to the internet alone than to antennas. 

Will wireless operators, who largely control distribution of mobile devices in the U.S., allow reception of 5G Broadcasting without a government mandate? If there is a government mandate, perhaps that mandate could require ATSC 3.0 devices instead. 

That raises some questions: Which technology is better? Which is easier to implement? I’ll provide some information and links to resources to help you answer those questions. 

A 3GPP Standard
5G Broadcast today is defined in 3GPP Release 17 (for an overview on the evolution of 5G Broadcast within 3GPP, check “Broadcast, multicast technologies,” by Dongwook Kim, 3GPP MCC. 

The current standard has features that support high-power, high-tower broadcasting. These include Receive-Only-Mode (no SIM card required) and a cyclic prefix of up to 200 microseconds, allowing larger distances between sites in a single frequency network (SFN). 

The major components of the 5G Broadcast signal are the CAS (cell acquisition subframe) which contains the PBCH (physical broadcast channel); PDCCH (physical downlink control channel), and the PDSCH (physical downlink shared channel) necessary to decode the PMCH (physical multicast channel). In order to receive a 5G Broadcast signal, a receiver must be able to decode the PBCH, the PDCCH, the PDSCH, and the PMCH. 

The PBCH, PDCCH and PDSCH are control channels that can be compared to the bootstrap, L1-basic and L1-detailed in ATSC 3.0, while the PMCH is similar to the PLP subframe in ATSC 3.0. The coding and modulation of  these components determines the robustness and capacity of the system. 

More information on the 5G Broadcast physical layer is available in “ETSI TS 103 720 Technical Specification” and in the IEEE Transactions on Broadcasting paper “Evaluation of ATSC 3.0 and 3GPP Rel-17 5G Broadcasting Systems for Mobile Handheld Applications.”

5G Broadcast Hardware/Software
Rohde and Schwarz has developed a 5G Broadcast platform that has been used for tests around the world. Fig. 1, taken from the company’s “5G Broadcast for Automotive” presentation by Dr. Nik Dimitrakopoulos, shows a R&S BSCC2.0 (broadcast service and control center) feeding a R&S SDE900 (the same model number unit used for ATSC 3.0 signal generation) into a TCE901 exciter and THU9evo transmitter. 

With the exception of the BSCC2.0, this configuration will be familiar to U.S. broadcasters. Fig. 2, from the BSCC2.0 product brochure, shows the internal architecture of that unit. 

The OpenAirInterface5g initiative has developed software that will run on a UHD/USRP based SDR. The last information I have on this is from 2019 for a configuration based on 3GPP Release 14. Details are available in the “FeMBMS/eMBMS E2E Prototyping using OpenAirInterface5G” presentation by Javier Morgade at Vicomtech. 

Fig. 3 shows a system using two Ettus B210 SDRs, the same model used in the GNU Radio ATSC 3.0 transmitter I described in a previous article.  

Comparing 5G Broadcast and ATSC 3.0 Performance
As in the 5G Broadcast system described earlier, ATSC 3.0 has elements that allow receivers to lock to the channel, get information on how to tune the channel, and decode the data. How these elements are implemented affects performance under different conditions. 

Table XI in the IEEE Transactions on Broadcasting paper Evaluation of ATSC 3.0 and 3GPP Rel-17 5G Broadcasting Systems for Mobile Handheld Application shows ATSC 3.0 performance gains for TU-6, India-Urban, India-Rural, and Seoul-SFN-3 channels for ideal estimation and linear estimation at speeds of 3, 40, and 120 km/hr. 

Performance gain of the ATSC 3.0 bootstrap versus 5G PBCH varied from a worst case -4.1 dB for linear estimation of a TU-6 channel at 120 km/hr to a best case +10.5 dB for linear estimation of the Seoul-SFN-3 channel at 3 km/hr. Bootstrap performance was better than PBCH in 20 of the 24 scenarios.

A comparison of PDSCH versus L1-Detail showed ATSC 3.0 performance gain varied from -3.0 dB to +5.0 dB. PDSCH was undecodable in 3 of the 24 scenarios. L1-Detail was worse than PDSCH in 8 of the 24 scenarios, although in six of these the difference was less than 1 dB. 

When comparing ATSC 3.0 subframe with PMCH, the subframe performed better at 5 Mbps, 10 Mbps and 15 Mbps in every channel, with PMCH undecodable in 8 of the 24 scenarios at 15 Mbps. The performance gain ranged from +15 dB linear estimation in a 10 Mbps TU-6 channel at 120 km/hr to +0.6 dB ideal estimation at 10 Mbps at 3 km/hr and 40 km/hr in an India-Rural channel. 

The study presented in the IEEE paper explains the ATSC 3.0 performance gain comes from the superiority of its BICM (bit interleaved coded modulation) components and, depending on the propagation channel, the time interleaver. The bootstrap performs worse than PBCH in non-line-of-sight channels with high mobility but otherwise bootstrap has better performance. In the comparison of PDSCH, L1-Detail performed better over line-of-sight but PDSCH was able to take advantage of the diversity provided by combining two PDSCH in non-line-of-site situations. 

Practical Implications: 5G Broadcast vs. ATSC 3.0
Broadcasters have ATSC 3.0 transmission infrastructure, but at this time don’t have consumer equipment beyond fixed TV sets and gateway devices. Qualcomm is adding 5G Broadcast support to its mobile device chipsets but no devices supporting 5G Broadcast are currently available to consumers. Prototype devices are available for both standards. When will consumers be able to purchase these devices? 

ATSC 3.0 broadcasts are already on the air in more than 70 markets in the United States. Currently there is only one 5G Broadcast station in the U.S., the experimental LPTV mentioned earlier. The 5G Media Action Group’s web site has details on 5G Broadcast trials as well as links to a GITHUB with 5G Broadcast reference tools. Expect to hear more about 5G Broadcast deployments around the world at the 2023 IBC Show. 

5G Broadcast can build on existing modems and 5G mobile device components. This should make it relatively easy for manufacturers to implement in mobile devices. ATSC 3.0 has an incompatible physical layer and requires additional hardware, which implies extra cost for mobile devices. Many ATSC 3.0 performance advantages come from time-interleaving which requires more memory. I’m not aware of 5G capability in any TV set. If 5G Broadcast is required in TV sets, what will that cost?  

The IEEE Broadcast Transactions paper shows ATSC 3.0 has a significant cost advantage for network deployment—fewer transmitters are required for equivalent or better coverage. Will that matter in the U.S.? 

5G Broadcast & ATSC 3.0 Together
What if we end up in a scenario where 5G Broadcast is available on newer mobile devices but not in TV sets and ATSC 3.0 is available in TV sets but not on mobile devices? What about automobiles? We’ve seen interest in using ATSC 3.0 for delivering content to automobiles and as shown in the IEEE paper, ATSC 3.0 has a performance advantage there, but if 5G wireless devices are already in the vehicle, that may give 5G Broadcast an advantage.  

One solution would be for a TV station to transmit both 5G Broadcast and ATSC 3.0 on the same channel. This would require using time division multiplexing (TDM) to share the channel. I described the demonstration at the 2023 NAB Show in my two-part review of the show in my June and July columns. 

For this to work, either or both the ATSC 3.0 or 5G Broadcast standards will require changes to their frame structure. Given the number of ATSC 3.0 TV sets already in use, any change to that standard will have to be compatible with existing TV sets. 

Will it Become a Reality?
FCC rules require broadcasters to deliver at least one free channel to the public in standard definition. During the transition to ATSC 3.0, the FCC has required broadcasters to ensure programming remains available to all viewers, including simulcasting on ATSC 1.0. It is unlikely the FCC will allow broadcasters to shut down both ATSC 1.0 and ATSC 3.0 and move to 5G Broadcast any time soon. Assuming interest in OTA TV continues, the number of ATSC 3.0 sets will continue to rise making a full transition to 5G Broadcast difficult.  

Without new spectrum, I don’t expect a significant number of 5G Broadcast signals on the air in U.S. broadcast bands until enough ATSC 1.0 spectrum has transitioned to ATSC 3.0 to allow 5G Broadcast to share spectrum with ATSC 3.0. At that time, some stations may be able to move to 5G Broadcast entirely while other stations carry their programming on ATSC 3.0 channels, similar to the way stations are transitioning to ATSC 3.0 now. Stations may also use TDM (time division multiplex) to share their channel between ATSC 3.0 and 5G Broadcast. Both assume FCC approval. 

Several visions for the future for 5G Broadcast/Multicast Rohde and Schwarz described in their presentations could apply to the ATSC 3.0 system. In the end, the choice will likely depend as much on marketing, business plans and consumer preferences as it will on technology. 

5G Broadcasting is continuing to evolve. 3GPP Releases 18 and 19 should make it easier for high-power, high-tower broadcasters to begin 5G Broadcast, either by itself or time shared with ATSC 3.0 when (and if) 5G Broadcast reception becomes available in mobile devices. 

The 2023 NAB Show exhibits and sessions demonstrated the future of ATSC 3.0 can extend beyond traditional over-the-air TV broadcasting. I’ll focus on three ATSC 3.0 innovations: Use of ATSC 3.0 to provide precision time and positioning services; efficient data transmission for radio over ATSC 3.0; and sharing an ATSC 3.0 channel with a 5G signal. 

Broadcast Positioning System
The topic of using ATSC 3.0 as a backup for GPS was discussed in the session “Delivering Traceable Reference Time for ATSC 3.0-based Broadcast Positioning System (BPS),” by Patrick Diamond of Diamond Consulting and co-authored with Tariq Mondal and Robert Weller from NAB and Andrew Hansen at Volpe Center. 

During the session they listed some of the critical services that depend on precise timing from GPS, including mobile wireless networks, equity trading systems and power grid synchronization as well as multiple services requiring precise position information. Loss of GPS timing, whether due to failure or intentional disruption, will have a significant impact on the systems we depend on—indeed, high-precision position, navigation and timing (PNT) has been recognized as a national security concern.

The concept of using ATSC 3.0 to provide precision time and positioning is not new. One of the questions I had about precision timing was how the differences in timing in the transmission chain were accounted for. For example, the length of the transmission line on a 2,000-foot tower will change with temperature, and timing in the path from where ATSC 3.0 time is generated to the transmitter site may also change. 

The system presented uses data from an Avateq receiver to compare the received signal timing with a precision reference—GPS if available, a local cesium or rubidium clock, or another ATSC 3.0 station with a precision reference are possible options—and send that information to the Triveni Digital Broadcast Gateway, which adjusts ATSC 3.0 clocks to within 200-nanosecond accuracy required by critical applications. By placing the timing data on a robust physical layer pipe (PLP), reception should be possible at signal-to-noise ratios below zero dB, allowing the BPS to work indoors where GPS signals aren’t available. 

This presentation and another one with details on the system used, “BPS ATSC 3.0 Broadcast Emission Time Stabilization System Proof-of-Concept” by Mark Coril of Triveni, Vladimir Anishchenko from Avateq and Tariq Mondal, are available in the NAB BEIT Conference Proceedings. The presentation, “Broadcast Positioning System (BPS) Using ATSC 3.0,” by NAB's Tariq Mondal, Robert D. Weller and Sam Matheny  featured at a recent meeting of the National Space-Based Positioning, Navigation, and Timing Advisory Board, is available online at gps.gov. Fig. 1 from the presentation shows the system configuration.  

Radio Over ATSC 3.0
At first, the idea of sending audio broadcasts (radio) over ATSC 3.0 sounds simple. The ATSC 3.0 standard includes options for Dolby AC-4 and MPEG-H multichannel audio. 

However, as Liam Power from ONE Media pointed out in the paper “Audio Services Over ATSC 3.0: A Proof of Concept,” transmitting audio to receivers in vehicles in a bandwidth-efficient manner is not that simple. Designing an efficient ATSC 3.0 radio system requires selecting an audio codec compatible with a wide range of clients that delivers sufficient quality using the least amount of bandwidth, finding a method for transmitting the audio in the ATSC 3.0 signal with the least amount of overhead and complexity on the receiver side, and selecting physical layer parameters that provide a reliable signal in a mobile environment. 

ONE Media found the xHE-AAC codec met audio requirements at bit rates as low as 24 kbps. Dolby AC-4 performed well at 48 kbps but due to encoder restrictions could not be tested at less than 48 kbps. Support for Dolby AC-4 is also limited in client devices, particularly on computers and mobile devices, compared to the HE-AAC family of codecs. For the proof-of-concept, HE-AACv2 was used as it currently has wider support than xHE-AAC. 

The proof-of-concept used the “UserDefined” table in the ATSC 3.0 standard to provide signaling information for the audio transmitted as a transport stream embedded in RTP UDP data. 

The demonstration used 16.66% of the total ATSC 3.0 signal capacity to provide 15 radio services at 45 kbps each (675 kbps total). A QPSK 11/16 modcod physical layer pipe (PLP) with a calculated 6.3 dB SNR requirement was used for audio. Test drives showed reception comparable (or better) than local FM radio stations.  Refer to the paper in the BEIT Proceedings for more detail on how the parameters were selected and potential improvement in future designs. 

ATSC 3.0 and 5G MIMS
In my last column I expressed doubts about support for combining ATSC 3.0 and 5G in a TV channel. At this year’s NAB Show it was clear the technology for sharing a TV channel with ATSC 3.0 and a 5G-compatible signal was still in active development.

In the NAB Futures Park, Korea's ETRI showed an ATSC 3.0 and 5G-MBMS signal sharing a single 6 MHz TV channel in a time-division-multiplex (TDM). The ATSC 3.0 and 5G signals were generated at different power levels to allow the switching to be displayed on a spectrum analyzer, (Fig. 2).

The 5G signal used 50% of the transmission time. For the demonstration, a single stream was transmitted on each signal at 5.77 Mbps for ATSC 3.0 and 5.21 Mbps for 5G-MBMS. The ATSC 3.0 signal used a non-uniform 64-QAM constellation with 8K FFT while the 5G signal used 64-QAM and 12K FFT. The code rates were similar so I would expect both signals to be close in robustness, with the ATSC 3.0 stream having a slight advantage. 

Rohde and Schwarz did not have a live demonstration of 5G/ATSC 3.0 channel sharing, but did show their work using TDM to share a TV channel with 5G. Rohde and Schwarz has experience in 5G transmission systems and at the 2022 NAB Show showed a high-power UHF 5G-MBMS transmitter. 

(Also read: What Can Broadcasters Do with 5G?)

Why would broadcasters be interested in sharing their channel with a 5G-compatible signal? If broadcasters are able to convince cell phone manufacturers and the wireless companies to include ATSC 3.0 capability in their phones there would be little advantage in transmitting content twice. 

However, the difficulty in getting FM radio enabled on cell phones—even when a device has the circuitry to receive it—shows broadcasters are likely to struggle to get ATSC 3.0 on mobile devices. Transmitting a signal in a compatible, physical layer format would make it easier for device manufacturers. Qualcomm, a major mobile device chip supplier, has indicated it will support 5G over UHF TV channels in its new modem chips. 

Transmitting a 5G physical layer signal along with a compatible ATSC 3.0 signal may be allowed under current FCC rules, and from what I saw at the show, equipment to do that will be available if customers demand it. That won’t happen unless devices become available that support 5G on UHF TV channels and wireless companies allow it on their devices. Until the transition to ATSC 3.0 is complete, ATSC 3.0 capacity is likely to remain scarce. How many stations will be willing to give up channel capacity to add a 5G signal? 

These technologies show ATSC 3.0 is ready to provide services beyond delivering TV to screens. Adding Broadcast Positioning Service capability requires little extra capacity, especially if LDM is used for the robust layer, and adding more than a dozen radio services over ATSC 3.0 can be done effectively in much less bandwidth than a 1080P HD signal as ONE Media demonstrated. 

Other work not mentioned here is being done to optimize data delivery over ATSC 3.0. When considering the role these “beyond TV” services could play in the future of broadcast TV, notice how cable TV has evolved from a service providing TV to consumers who could not receive TV on an antenna to a service most customers depend on for broadband internet. l

In Part 2 of my 2023 NAB Show coverage I’ll look at some of the interesting products I saw for RF transmission, reception and measurement. I welcome your comments, question, and observations on the future of broadcast TV. Email me at dlung@transmitter.com.

Last month the National Association of Broadcasters recognized something that TV Tech readers have known for decades: Doug Lung, long-time columnist for this brand and a member of the team that helped build the Telemundo network, has achieved the kind of career excellence that is worthy of this year’s NAB Television Engineering Achievement Award. 

When I arrived at TV Tech more than 20 years ago, Doug had already established himself as an expert on broadcast television, and in particular, RF technology through his monthly columns. As the fortunes of free over-the-air TV broadcasting have ebbed and waned over the years, Doug recently wrote in his 300th column that, despite all of this, “the good news is over-the-air TV broadcasting is still going strong.”

It’s hard to believe then, that Doug’s career path was not so certain when he started out nearly 50 years ago. As a practitioner of Transcendental Meditation, which was popularized in the late 1960’s by the Maharishi Yogi and the Beatles, Doug was in line to become a teacher of “TM.” When that didn’t work out, he chose another passion of his: broadcasting.  

Doug had gotten his start in radio and had gained a wealth of experience in the technical side of things. When there was an opening in 1974 for an engineer at the TM video facility in Livingston Manor, NY, Doug left Easton Pa., where he had just finished his third year at Lafayette College to take the job. 

From there, he moved to Los Angeles where he helped put KSCI-TV—which at the time was a non-profit TV station owned by the TM organization—on the air. “That was the first TV broadcast station I worked at,” Doug said.  

Eventually Doug ended up at the place he has called home for decades—Hawaii—when he helped fellow TV Tech writer Bill Hayes build out the transmission facility for KSHO, the state’s first full-powered UHF TV station. Doug fell in love with the area, partly because who wouldn’t, but also for the natural beauty of its volcanoes. 

In 1985, he led the engineering department for what was to become the Telemundo network and station group, assisting in the design, construction and installation of the company’s broadcast and cable facilities. Telemundo was acquired by NBC in 2002, where Doug eventually was appointed vice president of Broadcast Technology for NBCUniversal Local.

Over nearly five decades of experience, Doug has witnessed a great deal of TV history and when I asked him what project he was proudest of, I expected him to mention the transition to DTV that took place over several decades. But it was the return of broadcasting to New York after 9/11 that affected him the most.

“Working with engineers, manufacturers and the MTVA to get broadcasting up on the Empire State Building and eventually onto One World Trade Center—that was an incredible effort,” he said. “I just really feel honored to have been able to be a part of that.”  

So congratulations Doug on this well-deserved recognition! Doug will receive his award along with Radio award winner Michael Cooney with the Beasley Media Group at the “We Are Broadcasters Awards,” April 18 at 10 a.m. at the NAB Show in Las Vegas.

WASHINGTON—Doug Lung, vice president of Broadcast Technology for NBCUniversal Local and long-time TV Tech columnist, has been named recipient of the 2023 NAB Television Engineering Achievement Award. 

Doug leads NBC and Telemundo-owned stations’ RF and transmission affairs, including microwave, radars, satellite uplinks, and FCC technical filings.

Beginning his career in 1976 at KSCI in Los Angeles, Doug has nearly 50 years of experience in broadcast television engineering. Beginning in 1985, he led the engineering department for what was to become the Telemundo network and station group, assisting in the design, construction and installation of the company’s broadcast and cable facilities. 

Other projects include work on the launch of Hawaii’s first UHF TV station, the rollout and testing of the ATSC mobile-handheld standard, and software development related to the incentive auction TV spectrum repack.

Doug is also the longest-serving columnist for TV Tech, having launched his RF Technology column nearly 35 years ago. Doug is also a regular contributor to IEEE Broadcast Technology. He received a Tech Leadership Award from digital media publisher Future in 2021 and is a member of the IEEE Broadcast Technology Society and the Society of Broadcast Engineers.

Michael Cooney, CTO at Beasley Media Group will receive the Radio Engineering Achievement Award. Cooney is a recipient of the 2016 Radio World Excellence in Engineering Award. 

They will be honored at the We Are Broadcasters Awards, held on the Main Stage of the 2023 NAB Show on April 18 at 10 a.m.

Established in 1959, the Radio and Television Engineering Achievement Awards are given to individuals who are nominated by their peers for significant contributions to advancing broadcast engineering.

In my last column I took a look at the future of ATSC 3.0 broadcasting. This month I’ll talk about resources to learn more about ATSC 3.0 and revisit 5G broadcast. 

Early in the development of the standard, I wrote about how ATSC 3.0 works by explaining how guard intervals protect data from multipath, describing tools for calculating the tradeoffs between robustness and data capacity, exploring layered division multiplexing, and discussing the basics of OFDM (orthogonal frequency division multiplexing). 

Rather than repeat myself, I’ll share some websites and tutorials for more detailed, up-to-date and practical knowledge about ATSC 3.0. 

On the Web
The Pearl NextGen TV “Host Station Manual”  describes how to begin broadcasting ATSC 3.0, from program delivery to transmission. This guide has been used to successfully launch many of the ATSC 3.0 stations on the air today. The Pearl TV website also includes webinars on launching ATSC 3.0 that are available on request to broadcasters. 

For more in-depth technical information, SBE offers on-demand tutorials for SBE members. Members may also want to consider certification as an ATSC3 specialist. 

The ATSC 3.0 standard is very complex. If you want to understand the intricate details on how ATSC 3.0 works, dig into the ATSC 3.0 Technical Documents on the ATSC website for standards and recommended practices. 

ATSC 3.0 Recommended Practices lists documents dealing with ATSC 3.0 Field Tests (A/326), Guidelines for the Physical Layer (A/327) and more. The Physical Layer Guidelines (A/327) provides an excellent overview of how the ATSC 3.0 signal is generated and the trade-offs between different physical layer parameters. 

Visit the ATSC Implementation Guide: Emissions Testing Process for a checklist for ensuring ATSC 3.0 transmissions are functional and steps for dealing with receiver interoperability issues. 

With Your Transmitter
After learning how ATSC 3.0 signals are generated and about the different options for modulation and coding, you may want to do some experiments to see how they work. 

Experimenting with an on-air ATSC 3.0 station broadcasting the signals from multiple stations will likely be frowned upon. The solution is to set up your own ATSC 3.0 lab. This can be done using the Dektec DTU-315 USB-3 all-standard, all-band modulator or similar devices as I described in previous columns but there is a lower cost option for experimenters, albeit with some major compromises. 

Ron Economos, aka “drmpeg” researched the ATSC 3.0 standards and documents and built an ATSC 3.0 transmitter with a software-defined radio. I know it works because I was able to generate an ATSC 3.0 signal with his GNU Radio software and my Ettus B200 SDR and receive it on my HDHomerun ATSC 3.0 tuner. If the Ettus B200 is not available or too expensive, Chinese clones are available on aliexpress.com for under $600 and claim compatibility. Other lower-cost SDRs may also work with modification of the GNU Radio Companion flow graph.

 Ron’s github site has the software and some test streams. The software includes an option to add a second PLP using LDM. I had no problem getting that to work. As configured, the SDR will transmit on 429 MHz, or cable Channel 58. It can be changed to any frequency in the B200’s range. View the signal with the HDHomerun ATSC 3.0 receiver and the “hdhomerun_config” and “hdhomerun_config_gui”  programs. Step-by-step details on how I installed it on my Fedora 36 Linux laptop are in the winter edition (2022–2023) of the IEEE Broadcast Technology magazine. 

In the version I tested in December 2022, the software does not transmit LLS, which provides the signaling necessary for a receiver to recognize the signal, and it uses ATSC 1.0-formatted transport stream packets. It won’t work on TV receivers looking for the LLS and IP packets. The HDHomerun won’t find the signal in a channel scan but can be manually tuned.

If you have access to an MPEG-2 or MPEG-4 encoder that can add the basic ATSC 1.0 PMT and PID information, you can create your own ATSC 1.0 transport stream files. There should be a way to generate a compatible transport stream multiplex in software with gstreamer or ffmpeg but I haven’t found any examples on how to add the PMT and PID tables. 

At some point, after I add a Morse code IDer or figure out how to create a program stream with my ham call sign on it, I may hook this up to my outdoor discone antenna and see what the coverage looks like with a few milliwatts of ATSC 3.0. 

I’m especially interested in seeing how well the LDM robust layer works. While the SDR transmitter is based on the A/322 standard, using it with a full-power or Class A TV station probably isn’t legal, at least in the spirit of the law, as it won’t be compatible with existing ATSC 3.0 receiver designs. LPTV stations may have more flexibility in this area. Take a close look at the FCC rules and don’t forget the signal will have to meet FCC emission mask requirements. 

If you want to learn more about ATSC 3.0 inner workings, adding LLS and IP input capability (at least STL-TP input) to the program would be a great contribution.

ATSC 3.0 and 5G
In my last column I mentioned work being done by Rohde and Schwarz and Qualcomm on broadcasting content using 5G (3GPP) standards on UHF TV stations.  

I was overly optimistic about the ability of a TV station to transmit both an ATSC 3.0 A/322-compatible signal and a 5G broadcast signal on the same channel at the same time. Rohde and Schwarz has been participating in 5G broadcast demos at events such as IBC and Mobile World Congress so I asked them about this. 

The company said none of their tests have involved such a combination and while it is possible in a test bed configuration, such a combination is not currently supported by 5G broadcast and is not likely to be in the near future. These are two distinct and different physical layers. 

Qualcomm has been working to include 5G broadcast in its latest RF modem chips. The Qualcomm vision is outlined on its website, which had this comment on the 3GPP Release 16 enhanced TV standard: “It can be deployed in existing UHF spectrum (i.e., 470 to 698 MHz) that broadcasters already own or have access to, and its design allows the reuse of existing cellular modem building blocks.” More support for standalone 5G enhanced broadcast is planned for 3GPP Release 17 and 18 standards. 

If a system isn’t available that allows use of a channel for both ATSC 3.0 and 5G standalone broadcast, then at a minimum the FCC would have to eliminate the requirement for compliance with ATSC A/322 and any simulcast requirements before it could begin in the United States. It may be possible for LPTV stations to transmit 5G broadcast signals but depending on the characteristics of the signal, that might require a waiver. 

Over the next few years, if 5G broadcast is deployed on UHF TV stations it will be interesting to see its impact on free over-the-air TV and today’s TV broadcast system.

I welcome your comments, questions, and observations on the future of broadcast TV. Email me at dlung@transmitter.com. 

I started writing RF Technology columns for TV Technology (now TV Tech) 31 years ago and this article represents my 300th column. In the 1980s, before starting my column I did some reviews on equipment such as a Leitch VITS inserter and the Abekas A42 still store. Given the timing, these may have appeared in Radio World magazine, before TV Technology became a publication. 

Those were done on a typewriter, and I have no archive files. My report on building a Townsend CST transmitter from a kit of parts, delivered just as Townsend entered bankruptcy, was likely what prompted the editors of TV Technology to suggest I start a monthly column on RF technology back in 1991. 

I took a look at my 200th column (actually my 201st column since one earlier column was so long the editors had me split it into two columns) to see what I was thinking about then. I noted the decreasing number of viewers using antennas and the demand for spectrum for wireless carriers. I wrote: “I believe the future of over-the-air TV broadcasting will be determined soon, probably within the next two years.” 

What's Changed?
The good news is over-the-air TV broadcasting is still going strong 12 years later, in part helped by money broadcasters received as part of a spectrum auction that resulted in the transfer of 14 UHF-TV channels to wireless carriers and by viewers dropping cable TV. Those funds helped broadcasters upgrade their transmitters and antennas and prepare for the transition to the next-generation digital standard, ATSC 3.0. 

Although I acknowledged then that solid- state transmitters were becoming viable options for UHF-TV transmitters up to 10 kW, I never imagined that only five years later I’d be ordering a 108-kW solid state Rohde and Schwarz transmitter for installation at One World Trade Center. 

The use of Doherty amplifiers allowed solid- state amplifiers to exceed the efficiency of the IOT (inductive output tube) amplifiers and approach or exceed the system efficiency of MSDC (multi-stage depressed collector) IOT amplifiers. The move from tube-based transmitters and the transition from analog signal generation to signals created in the digital domain in FPGA’s and software-defined transmitters was perhaps the most significant technology change since I started writing for TV Technology. 

The Future of Over the Air TV
Twelve years ago, I wondered about the future of over-the-air TV. Based on the number of questions I receive about over-the-air TV reception and the growing number of sales and ads for TV antennas, I see a good future for over-the-air TV. 

That isn’t to say there aren’t risks. Viewers are dropping their cable TV subscriptions in favor of streaming video over the internet. Since local TV stations are not available for free online, this leads viewers to install antennas if they value local TV. If TV station owners decide to allow free streaming of their over-the-air programming, this could slow the adoption of antennas. 

At some point, the number of viewers could drop to the point where maintaining a strong over-the-air signal or even dealing with the responsibilities the FCC places on TV licensees might not make sense if most of the audience was watching via the internet. 

One thing broadcasters can do to preserve over-the-air broadcasting is to make it easy to receive. The move from analog to digital helped as most viewers now get a perfect picture and a huge number of programs, often with something as simple as a $20 indoor antenna. 

The transition to ATSC 3.0, with its more robust transmission options (including single frequency networks) should make reception easier. Broadcasting a compatible 5G signal could open access to cellphones and tablets. The ATSC 3.0 standard would allow transmitting a signal in the ATSC 3.0 A/322 format to TV sets along with a 5G physical layer to cell phones and tablets using time domain or frequency domain multiplexing. 

Qualcomm is developing chips that will allow reception of 5G broadcasts on UHF-TV spectrum in cellphones. While it may be difficult to convince wireless carriers to allow this in devices they sell, broadcasting is still the most efficient way to deliver content to a huge number of viewers—there may be ways to encourage coverage through sharing ads and viewer data. 

I strongly believe the success of ATSC 3.0 will depend on how easy it is to receive on the largest number of devices. If broadcasters make it too difficult for manufacturers to build ATSC 3.0 receivers or require viewers to go through extra steps to receive the signals, it will be tough to make the transition from ATSC 1.0 to ATSC 3.0. It is great to see companies like VBox and SiliconDust offering low-cost ATSC 3.0 receivers that will work with existing TV sets. 

I’m still waiting for a low-cost ATSC 3.0 USB dongle and wonder if they will work with open-source software when they do become available. I follow open-source DTV software and device driver development on the linux-media mailing list and there is now little activity for ATSC 1.0 and none related to ATSC 3.0.  

One of the challenges broadcasters face with ATSC 3.0 is the need to protect content from unauthorized distribution without hurting adoption of ATSC 3.0. Without this protection, program providers may be reluctant to offer their best content to broadcasters. Managing digital rights will be important. It shouldn’t be too difficult for manufacturers and software developers to have their devices and programs certified. Fortunately, since ATSC 3.0 is IP-based, the same protections viewers have gotten used to when viewing Netflix, Peacock, Hulu, Amazon Prime or other streaming services should work with ATSC 3.0. 

If authentication and decryption can be handled in an existing browser or browser plug-in, it should be easy to build and distribute low-cost ATSC 3.0 tuners that work with a qualified browser for displaying content. If broadcasters can match the experience people have with protected streaming content, content protection should not hinder ATSC 3.0 adoption on devices beyond TV sets. Even with content protection, I would expect most content to be available for free with minimal, if any, user registration requirements. 

The Future of RF Tech
I’ll be describing developments with ATSC 3.0 and other RF technology topics in future columns. 

The audience, and as a result, the content, of my columns has changed over the past thirty years. Past columns described simple, easy-to-build remote controls using off-the-shelf computer modules that when attached to a dial-up modem, allowed a simple way to monitor remote sites, particularly low-power and translator sites. I had tips on doing calormetric RF power measurements, the best way to aim microwave dishes, and tuning external cavity klystrons. 

I covered path-loss calculations for microwave systems, RF exposure calculations, and coverage predictions using open-source software. As the ATSC 3.0 standard was being developed, I wrote several articles on how the ATSC 3.0 physical layer works and how it differs from ATSC 1.0. 

In recent years I found there is more interest in receiving over-the-air TV, measuring signals, optimizing coverage and practical tips. This is partly due to the simplification of the transmission path. It is no longer necessary to spend hours optimizing a transmitter’s analog exciter and solid-state transmitters don’t require tuning. With regards to tutorials, in the past 299 columns I’ve covered so many topics I have to be careful about repeating myself! Some are available by Googling “Doug Lung” and the topic. 

Many of the best ideas come from readers. I welcome your questions, comments and experiences. Let me know what you would like to see in future columns. Which topics have you found most useful? Would you like to see more in-depth technical topics, less technical practical tips, basic tutorials like my last column, or “build-it” projects (both hardware and software)? Email me at
dlung@transmitter.com.

As I approach my 300th RF Technology column for TV Tech, I thought it might be useful to describe some of the things I’ve learned in more than 50 years of working with broadcast transmitters. Throughout my career, I worked with concepts and systems that were difficult to understand, but through experience and help from experts I was fortunate to meet I was able to understand them better.

You’ve probably had similar experiences, from things as basic as learning to drive to creating spreadsheets on a computer or configuring an IP network. One element of this is being able to understand how these systems or tasks work on an almost intuitive level. That provides the basis for additional learning and expertise even across different fields. 

I’ve found many people who have built a good understanding of IT are also quick learners when it comes to RF systems. Over the years, I’ve noticed more of my readers are not engineers with RF backgrounds, but people, often with experience in other fields, who are interested in RF. This month’s column is for them, as I’ll be covering some basic principles. If you have had experience with RF, I welcome your comments on other RF topics non-engineers would find useful.

One thing that helps in gaining an understanding of how RF works is finding ways to see it work. Radio frequency electromagnetic fields are similar in many ways to much higher frequency energy, such as light. Just as buildings block some light and create shadows, they also block RF. 

However, the shadows are not completely dark, as some light finds its way in by reflection from other objects and scattering in the atmosphere. RF behaves the same way, although the amount of reflection and scattering in the atmosphere will vary with frequency and wavelength, which is the frequency divided by the speed of light. 

Comparing RF to Light
Like light, RF energy can be focused. In transmit antennas, this concentrates the power on the ground and can be used to target specific areas while avoiding others where coverage isn’t needed or interference has to be reduced. In receive antennas, the focusing provides gain, which, like a telescope, increases the intensity of the signal coming from one direction and reduces signals from other directions that may cause interference. 

As RF frequencies increase and wavelength decreases to a millimeter or less, antennas can even start looking like optical devices. At satellite and microwave frequencies, parabolic reflectors are commonly used. These also turn out to be quite effective at light and infrared wavelengths, as anyone who has had an LNB cover melt when the sun moved behind the satellite the dish was looking at knows.

Antennas and Wavelength
Keeping in mind the relationship between frequency and wavelength can also help in evaluating antennas. Antennas that have to work on lower frequencies, like low-band VHF-TV (54–88 MHz), FM radio (88–108 MHz), have to be larger than those used for high-VHF TV (174–216 MHz) or UHF TV (470–608 MHz) to work efficiently. This doesn’t mean small antennas won’t work at the lower frequencies for reception, just that the antenna itself will be less efficient. 

One solution is to add an amplifier. However, the amplifier will add its own noise, reducing sensitivity, and because the small antenna will be less directional (focused) it will pick up more surrounding noise and interference. For best results, a low-noise amplifier should be located at the antenna where it can offset the loss in the line to the TV and provide a good match to the line. 

On the transmit side, matching the resonant frequency and impedance of the antenna to the transmitter is more important. Without getting into the math, matching the impedance is like connecting two pipes of the same diameter together with the faucet on one end supplying water at the optimum rate for the pipe and the device (say, a turbine in this analogy) at the other end. The water flows smoothly with the least amount of loss. 

The same analogy applies in a system with a transmitter, transmission line and antenna. However, if the impedance of the components isn’t matched, it will lead to excessive current (causing heating) and voltage (potentially causing arcing) at different points in the system, depending on wavelength. 

Most broadcast systems are well-matched, unless the antenna is damaged so problems are more likely to occur when a connector starts to lose contact, increasing loss and heat leading to contamination in the line, perhaps due to carbon created by overheating from a bad contact. 

In most cases failures will create a mismatch in the line, which can be located at the base of the tower either by sending a very short pulse up the line and looking for the time it takes for the return reflection, or sweeping the frequency across a band of frequencies (and different wavelengths) and looking at the time domain response across the frequencies. Because these measurements involve “sweeping” between frequencies, this is often called “sweeping the line.”

TV Antenna Specs Debunked 
One of the things that bugs me when reading reviews for TV antennas or looking at ads is comparisons based on range in miles or antenna gains that include a built-in amplifier. More responsible manufacturers will include the gain of the antenna at different channels. Most are based on gain above an isotropic antenna (without going into details, a “perfect” antenna) as “dBi” rather than gain above a dipole or “dBd” (like a set of rabbit ears with total length of half a wavelength). Gain in dBi will be 2.15 dB higher than gain in dBd. Ideally the specifications will specify whether the gain is in dBi or dBd. 

The range numbers in antenna ads should be ignored, as they eliminate too many factors, such as the height of the transmit antenna above ground. Just as light diminishes quickly after the sun sets, when the transmitter’s antenna is below the radio horizon the signal will drop off quickly. Read my TV Tech column “Estimating Coverage: Quick Analysis for Facility Mods,” for more information. 

For a transmit antenna 2,000 feet above average terrain, the radio horizon is 63.3 miles away. As the signal drops off quickly beyond this distance (as with light past sunset) ranges of more than 70 miles only would apply from mountaintop to mountaintop or for very high transmitter sites. 

Experimenting With RF
The best way to get comfortable with RF is to experiment with it. While difficult to do on the transmitter side (unless you are a licensed amateur radio operator) there is a lot that can be done on the receive side. Check out my article “Inexpensive Tools for RF Field Measurements” for more information. 

The Airspy Software Defined Radio (SDR) is a great way to explore the RF spectrum. It cannot demodulate broadcast TV signals, but it will show the TV signal’s spectrum and signal strength. A handheld spectrum analyzer like the TinySA (read my column “tinySA: Finding Interference and Aiming Antennas”) is a great way to explore RF spectrum. 

I got an email from a reader who was seeing some odd behavior picking up distant stations in Chicago. He was interested in trying out different antennas and locations, so I suggested he get a tinySA. He did and is now able to see how antenna type, orientation and location impact the signal. He noticed the ripple (“spikes”) and I explained those were due to reflections. With a bit of time and tinySA, he now understands more about TV reception than many people today who work in broadcasting.

A clarification: In my article “RF at the NAB Show—ATSC 3.0, Part 1” I said Saankhya Labs developed their multi-standard ATSC 3.0 tuner in cooperation with Coherent Logic. Vasanth Shreesha from Saankyha said, “The Saankhya ATSC 3.0 receivers use our own chipset (SL3000 or SL4000)” and they were not developed by Coherent Logic.” 

Email me at dlung@transmitter.com. I try to answer all emails promptly, but if I’m busy and the email gets buried, I might miss it. If you don’t get a response within a week or so, email me again.

Part 2 of 2

In my last column I focused on ATSC 3.0 measurement gear at the 2022 NAB Show. This month I’ll review some of the other items I found interesting at the show and look at the Broadcast Engineering Conference’s discussion on using drones for tower inspections. 

Transmitting—5G for Broadcast?
I wasn’t expecting any breakthrough technology in high-power UHF transmitters in Las Vegas but I did find time to visit three manufacturer’s exhibits and saw some interesting products. Rohde and Schwarz (R&S), which has been promoting the use of 5G for broadcast in the United States, featured its 5G transmitters for broadcasting. I wanted more details as I really didn’t understand how U.S. broadcasters would use 5G transmitters.

Since the ATSC 3.0 standard allows signaling different types of waveforms in the bootstrap signal, I thought R&S might be looking at using 3GPP 5G standards in the UHF TV band. It turned out R&S envisioned using these on existing UHF 5G wireless bands licensed to wireless operators in the U.S. One idea was that broadcasters—with their high-power, high tower sites—could provide low-cost, wide-area coverage. 

A more likely scenario is wireless carriers will roll out their own 5G broadcast system and compete with broadcasters for content delivery. It will be interesting to see how this develops. For an example of how 5G and ATSC 3.0 could co-exist, Google the HP Enterprise business white paper “The Convergence of 5G and ATSC 3.0 Opens a New Era of Communications.”

Hitachi-Comark had a new compact, all-in-one transmitter built on their successful Parallax series. The transmitter uses liquid cooling with dual pumps for both the amplifiers and in-cabinet mask filter. Maximum power output for the EC700HP-BB3 is 13.2 kW. Installation is simple as it only requires hooking up power and running hoses to the outdoor heat exchangers. If that’s too much work, an air-cooled E-Compact transmitter line does not require an outdoor heat exchanger, but obviously sufficient air flow (and perhaps cooling) is required.  

The simple installation of these transmitters could make them ideal for disaster recovery or backup, although the mask filter would have to be tuned to the desired channel if shared between stations.  

Anywave also had more powerful UHF amplifiers, with a 4.5 rack unit “Marble” series transmitter providing outputting 2,200 watts. It uses the latest Ampleon BLF989E ninth-generation LDMOS chip, rated at a peak power of 1 kW and average power of 180 watts per device. Proper cooling will be essential for these compact devices.

What I found most interesting was Anywave’s chart showing a new gap filler design using a reference antenna. This is used to characterize the booster’s transmitter reflections from the surrounding environment. Anywave claimed rejection of the transmitted signal into the gap filler of up to 50 dB, allowing higher power. Download http://anywavecom.net/wp-content/uploads/2022/04/Anywave-Gap-Filler-Indoor-Flint-Series-Product-Specification-4-22.pdf for more data. I expect low-power gap fillers to become more common as ATSC 3.0 is deployed.

Innovation from South Korea's ETRI
The Korean booth at the NAB Show usually has some interesting ATSC 3.0 technology and this year was no exception. ETRI described a system using MIMO and a 1024QAM constellation to transmit over 100 Mbps in a single ATSC 3.0 RF channel. The design requires separate transmit antennas (one for horizontal and one for vertical polarization) and a receive antenna with separate outputs for horizontal and vertical polarizations.

This is obviously incompatible with existing receive antenna installations, so I asked if LDM could be used to provide a robust non-MIMO layer at reduced bandwidth for viewers without the outdoor dual-polarized antennas. I was told it was possible, but greatly increases complexity. 

A more likely scenario would be a station provides only high-data rate service, requiring a special receive and likely professional antenna installation. A pay-only service might be possible if FCC subscription TV rules used by analog for-pay OTA companies like On-TV apply to digital broadcasts as well. Google “ETRI ATSC 3.0 MIMO” for a number of articles on the technology, many in Korean (use Google translate). 

Inspecting With Drones
In a Broadcast Engineering Conference presentation at  the NAB Show, Paul Shulins with Shulins Solutions showed how he uses drones to examine the thermal characteristics of antennas and transmission lines. TDR (time-domain reflectometry) measurements with a vector network analyzer can reveal major issues with transmission line connections but are less useful pinpointing problem areas inside antennas or heat-related problems that don’t change the line impedance. 

Shulins uses a drone outfitted with a special IR camera able to detect minor temperature differences in the line. This is more complicated than it may sound at first because the outer on copper transmission line, particularly new line, tends to reflect IR and hide internal heating. Measurements are best made before the sun has had a chance to heat the line. This IR imaging as proven it's worth in several cases, which Shulins outlined.

All it takes is one bad transmission line connection to eventually take a station off air and potentially cause expensive damage to many sections of transmission line. In Fig. 1, a thermal image shows the hot spot in a line due to a bad “O” ring that resulted in damage to 150 feet of transmission line. In Fig. 2, the arrow on the visual image provides a higher resolution view of the line. 

Due to the time of day when the visual image was taken there wasn’t much light. I stretched the contrast on the images to make the less illuminated and heated parts of the line and the tower more visible. The fault was not visible in a ground-based TDR sweep of the line. I’m now recommending IR inspections on new line installations to avoid future problems. For more information, visit https://shulinssolutions.com/drone-tower-inspections for more information.

Jason Schreiber, CEO of RF measurement provider SixArms, presented a paper on using drones to measure antenna patterns. I’ve covered drone antenna measurements in previous columns, so I won’t repeat the details. He noted measurements found several antenna patterns that didn’t match the expected pattern. In about 80% of the cases, they were due to installation errors, a common problem being the antenna rotated by one bolt hole. Manufacturers’ defects were less common. 

Of course, tower reflections result in measured patterns from side-mounted antennas being quite different than the free-space patterns. While ground measurements were enough to find that error, drone measurements would be required to discover more subtle discrepancies. SixArms also had some new measurement equipment at the NAB Show (for more information, visit www.sixarms.com). 

Testing NextGen TV on the Road
For ATSC 3.0 reception on the road, I have an early Airwavz Redzone receiver using the original LG demodulator.The SiliconDust ATSC 3.0 IP HDHomeRun gateways use the new Sony chip and in my limited testing seem to perform better than the old Airwavz tuner. 

The problem is the SiliconDust tuner requires an IP connection. Just hooking it up to the laptop’s Ethernet port results in complaint about no Internet access. I have found a way using NetworkManager in Linux to configure a shared connection between a wireless Internet link and the device and the laptop, but it is complicated. 

A much simpler solution was to buy the small TP-Link TL-WR902AC AC750 wireless travel router that connects to the hotel WiFi, provides an Ethernet port for the SiliconDust tuner, and a wireless connection to the laptop for both. The device may also come in handy when working on equipment in the field that requires an Ethernet connection as the equipment could be connected by cable to the router and accessed anywhere in the room on a laptop using WiFi—no need to string an Ethernet cable across the floor. 

As always, I welcome comments and questions. Email me at dlung@transmitter.com. I try to answer all emails promptly, but if I’m busy and the email gets buried, I might miss it. If you don’t get a response within a week or so, email me again.

TV Tech's sister publication Broadcasting + Cable has named the recipients of the 2021 Technology Leadership Awards.

The awards, which B+C started in 1999, honor individuals who have made significant contributions to how TV, digital and streaming media companies use technology.

The 2021 Tech Leadership Awards winners are:

• Greig Fraser, director of photography/producer;
• William Hayes, director of engineering and technology, Iowa PBS;
• Lucinda (Cindy) Hutter Cavell, vice president, Cavell, Mertz & Associates;
• Brett Jenkins, executive vice president and CTO, Nexstar Media Group;
• Yvette Kanouff, partner and CTO, JC2 Ventures;
• Jaya Kolhatkar, executive vice president, data, Disney Direct-To-Consumer;
• Barbara Lange, executive director, Society of Motion Picture and Television Engineers (SMPTE);
• Doug Lung, vice president broadcast engineering, NBC Owned Stations;
• Phil McKinney, president and CEO, CableLabs; and
• Phil Wiser, executive vice president and global chief technology officer, ViacomCBS. 

In addition, B+C is introducing a new award for “Technology Leadership Award for Building Diverse Tech Teams,” which will be given to Stephanie Mitchko-Beale, executive vice president & chief technology officer, Charter Communications.

PLUS: What Are the Tech Leadership Product of the Year Awards?

“This year’s winners highlight the growing importance of tech innovation in helping media companies navigate rapid changes in their businesses,” said Kent Gibbons, content director, Broadcasting + Cable. “The innovative tech strategies they’ve pursued during their careers have both helped companies build new business for the digital age and provided consumers with higher quality content and access to content in new ways.”

Recipients will be profiled in the March 22 issue of B+C as well as the April issue of TV Tech. The awards will be presented virtually during the Technology Leadership Summit March 23 and 24, 2021.

For more information and to register for the Technology Leadership Summit, which is produced by B+C, TV Tech and Multichannel News, click here.

Long time readers know I like to test compact and, where possible, low-cost equipment. Recently I found another tool to add to my backpack when I get back on the road. 

Seven years ago, wanting a spectrum analyzer I could throw in my laptop bag, I spent around $500 (I don’t remember the exact price) for a 5 GHz spectrum analyzer a bit bigger than a USB flash drive from Triarchy. The company is still around selling miniature USB spectrum analyzers that can cover frequencies up to 8.15 GHz. I’m sure the analyzer and associated software have improved since I bought my unit.

Recently we’ve seen the introduction of a number of innovative, low-cost, RF instruments. The NanoVNA, which I’ve written about before, is one of those and the basic design has been improved to where the performance is now close to units costing orders of magnitude more. 

It seemed to me that with the right firmware, the NanoVNA could be turned into a spectrum analyzer. As far as I know, that hasn’t happened, but I found the tinySA spectrum analyzer for around $50! Details can be found at www.tinysa.org/wiki. 

The unit is sometimes available in the U.S. from R&L Electronics or direct from China at the Zeenko Store on AliExpress. I ordered mine from another store I trusted on AliExpress and it took a month to arrive. Half that time was spent making it through USPS mail after it arrived in the United States.  

POSSIBLE PROBLEMS

Before you get too excited, this unit, like the first NanoVNA units, has limitations. However, within its primary frequency span from 0.1 to 350 MHz and even the expanded “high” range that goes to 950 MHz, it is quite usable and offers some features not present in my older Triarchy analyzer. While it is not much bigger than a USB ATSC tuner, it includes a rechargeable battery and a tiny 2.8-inch (diagonal) LCD touchscreen.

The tinySA low input for frequencies below 350 MHz has filtering and adjustable attenuation in 1 dB steps between 0 dB and 31 dB. It includes a built-in level calibrator for this input and after calibration specified accuracy is +/–1 dB. With a resolution bandwidth of 30 kHz it can detect signals down to –102 dBm. Spur-free dynamic range is 70 dB at that resolution bandwidth. Frequency accuracy is specified as the selected resolution bandwidth, which can be set to 3, 10, 30, 100, 300 or 600 kHz or set to “auto.” Not bad for $50.

I know many, if not most, readers will be interested in how it performs using the “free” high input that covers from 240 MHz to 950 MHz. The first thing to know is there is no filtering on this input and no internal attenuation. Filters and attenuators can be obtained from RF component manufacturers like Mini Circuits and added externally. While the input impedance of the low input is 50 ohms if 10 dB internal attenuation is added, without an external attenuator the impedance of the high input will vary. The high input also does not work with the internal level calibrator, so for calibration an external reference is needed.

Since there is 100 MHz of overlap between the low and high inputs, you can use the low input to measure a signal in the overlap band and then switch it to the high input and manually adjust the level calibration to match (at that frequency). Without the filtering, the high input is also subject to images. The firmware includes an option to mask nearby “mirror images.” When using this to look at DTV signals in the UHF TV band I did not find images to be an issue.

Fig. 1 shows a screenshot of the FM band as seen at my house. The third signal from the left (90.7 MHz) is coming from Maui, which is 94 miles away with at least one obstruction. The four stronger signals are from a site only 2.4 miles away, with one obstruction.

Fig. 2 shows a scan of the UHF TV band. The Channel 36 signal (far right) is from a 213-watt ERP translator 5.5 miles away and line of sight. The tilt is due to roll-off from the Antra ATF-600 LTE filter. The Channel 28 signal is interesting as the K28JV transmitter site is in the opposite direction (in Hilo) and blocked by terrain. None of the other Hilo stations are visible in the plot. Even with the compromises on the high input, the performance isn’t bad.

The high input should work fine at UHF for things like tracking down interference to wireless microphones or aiming TV antennas, but it is probably a good idea to add a 10 dB attenuator or two to the high input if working in a strong signal environment. I have not had a chance to test the tinySA at a broadcast site such as Mount Wilson. I fear the plastic case will lead to problems even with input attenuators. The tinySA wiki warns about this in its “limitations” section.

AVAILABLE SOFTWARE 

The 320x240 pixel screen will limit measurement resolution but some early software is available for using the tinySA with a PC. The page also has a link to a version of tinySA-Saver based on NanoVNA-Saver that will run in Linux or Mac OS. The instructions, however, appear to be written for use with a NanoVNA, not a spectrum analyzer and unfortunately most of the tinySA settings are not available in tinySA-Saver, at least that I could see in the version tested in early January. The tinySA-App for Windows worked quite well and was used to generate the screenshots for Figs. 1 and 2. The app can switch between the low and high modes.

There is obviously room for improvement here. In the FAQ section of the wiki the designers indicate more advanced (and expensive) units may be offered if there is enough interest in the $50 unit to justify production. Considering the size and cost of a signal meter for aiming a TV antenna or a larger portable spectrum analyzer, it was an easy decision to spend $50 for a device that not only provides an amplitude indication but also a spectrum display and can fit in my shirt pocket. I wouldn’t mind spending $150 for a unit with wider frequency range, a metal case and perhaps a 4-inch screen.

As always, I welcome comments and questions. Email me at dlung@transmitter.com. I try to answer all emails promptly, but if I’m busy and the email gets buried I might miss it. If you don’t get a respond within a week or so, email me again.  

Recently I got a call from Bob Gonsett concerning interference he started receiving on a TV set at his outpost in Fallbrook, Calif. Broadcast engineers in southern California know Bob and his engineering work at his firm Communications General Corp. He has been active in Southern California broadcasting for as long as I can remember, beginning with services such as the FCC-required frequency measurements for analog TV stations, as well as providing engineering for AM, FM and TV broadcast stations in the area.

While the FCC no longer specifies frequency tolerances for DTV stations—they simply have to stay within their channel and meet FCC emission mask requirements—many stations still use Bob to keep an eye on their frequency and also look out for potential interference from new co-channel stations.

Using a spectrum analyzer, Bob was able to trace the interference to a 600 MHz LTE signal. He expects this will become more of a problem for over-the-air TV viewers as wireless carriers build out small-cell distributed antenna systems that place the base station antennas very close to viewers’ homes.

He solved the problem in his house by building a simple quarter wave stub filter. With a quarter wavelength of coaxial cable, the impedance at one end is inverted at the other end. If one end is left open, the other end will present a short at the quarter wave frequency, acting as a notch filter.

I found a website that calculates the length for different types of coaxial cable (the velocity factor will affect the length) that makes it easy to design a quarter wave filter. Fig. 1 shows a picture of the filter from arcticpeak.com. A search on “quarter wave stub filter” will bring up other options. If the length of the stub becomes too short to easily work with, odd multiples of the length will also work, but there will also be a notch at a lower frequency—one-third the frequency for a three quarter wave stub, which could impact VHF Channel 12 or 13.

USING A FILTER

The majority of the licenses in the 600 MHz band belong to T-Mobile, which is moving quickly to build out its 600 MHz spectrum for 5G now that TV stations have vacated the band. The base stations transmit in the 617–652 MHz downlink band and receive signals from consumer devices transmitting in the 663–698 MHz uplink band. With the spectrum licensed in 5 MHz blocks, a quarter wave stub filter may be sufficient to notch out one 5 MHz block, but as more blocks are used, a more complicated filter will be needed.

I used an RTL-SDR and the Linux qspectrumanalyzer software to look at the 598–640 MHz spectrum at my rural location in Hawaii. The only TV station I can receive here is on Channel 36. Fig. 2 shows the spectrum, with surprising strong signals in the 600 MHz downlink band. Note the analyzer was hooked up to my vertically polarized discone antenna (with no preamplifier) so the Channel 36 signal, which is horizontally polarized, is not as strong as it is on my TV antenna with an LNA.

I’ve written before about using Channel Master’s LTE filter to block LTE signals above 698 MHz. They now offer a filter for 600 MHz interference.. Look at the spectrum plots on the web page and at the frequency range specified in the markings on the filter on the Channel Master store page (Fig. 3).

The upper pass frequency is shown as 599 MHz and the rejection starts at 600 MHz. DTV Channel 36 starts at 602 MHz, which would indicate this filter will not work in areas with a Channel 36 (like KNBC in Los Angeles) and reception may be compromised on Channel 35 stations (596–602 MHz) like WNBC in New York.

Channel Master’s technical specifications for the filter show “Frequencies Pass” as 5–609 MHz and “Frequencies Block” as 610–2,000 MHz. If this is the case, it should work fine. Since the LTE downlink band doesn’t start until 617 MHz, there is no need to have the filter reject frequencies in Channel 36.

I wanted to order one of the Channel Master filters to test the actual frequency response but Channel Master will not ship to a post office box and I wasn’t willing to spend the almost $60 they wanted for a $19 filter shipped to my physical address.

An Amazon search showed several companies selling LTE filters but most only blocked signals above 700 MHz. The Antra ATF-600 5–600Mhz 4G LTE ($15.99) looks like it might work but I could not find any detailed specs. The Amazon description also has this disclaimer: “This item will NOT work if interference signal is within 0–700 MHz,” which contradicts the description above it that says: “Removes interference above 600 MHz (CH36) that are coming from Cell Towers, Cell phones or other RF sources, purifying HDTV signals.” From the photo on the Amazon listing it appears there is also an ATF-700 filter, which has a cut-off frequency at 694 MHz. I’ve ordered the Antra ATF-600 and when it arrives I’ll hook it up to my NanoVNA and plot the frequency response.

The 600 MHz LTE interference is more likely to be a problem for TV viewers using an outdoor antenna with a preamplifier. The TV tuners in most TV sets still offer the option of scanning cable TV channels, which means they will be capable of receiving signals up to 800 MHz or higher. The newer silicon tuners offer good tracking filters but are subject to overload if the interfering signal is strong enough. The preamplifier can boost the interfering signal to the point where it can overload the TV tuner. Manufacturers of TV amplifiers have recognized this and are now selling amplifiers with 600 MHz LTE filters.

Digitenna’s preamplifiers are now available with 20–30 dB attenuation above Channel 36. The filters pass up to 610 MHz so Channel 36 reception should not be affected. Before ordering Digitenna products, verify the amplifier is one with the new LTE filter. I found another amplifier from Kitz Technologies that looks interesting. The KT-700 Amplifier includes an LTE filter that starts at 620 MHz.

Channel Master’s LTE filter product page says their “Amplify” preamplifier includes an LTE filter, but the specs show a 700 MHz cutoff, which won’t help with the 600 MHz band interference if that frequency is correct. 

CORRECTION AND UPDATE

Since my last column (“Antennas: Back to the Future,” September 2020) the reader using the HD-Stacker antenna sent me some close-up photos of the feed system and some comparisons with another antenna.

He wasn’t happy with the performance of the HD-Stacker and after contacting the manufacturer and not getting a satisfactory response, decided to try the $40 Winegard Freevision FV-30BB I’d been recommending for noncritical applications. He was surprised to find that in his location it performed as well or better than the HD-Stacker.

That’s hard to believe, but a possible reason is the size of the Winegard allowed it to be mounted in a more favorable location. The feed matching and VHF/UHF combining may have hurt performance since the high-impedance VHF and UHF driven elements are simply paralleled with a section of twin-lead with no apparent attempt to match or isolate them. Replacing that “combiner wire” with a dual input LNA would likely have significantly improved the HD-Stacker’s performance.

Another reader notified me that the https://groups.io/g/NanoVNA-V2 website I mentioned as a forum for the low cost NanoVNA-V2 vector network analyzer is an impostor website. The real forum is at https://groups.io/g/NanoVNAV2. I apologize for the error. Visiting the real website I found that the NanoVNA-V2 is now available with a case (the Plus 4) and offers measurements using the fundamental frequency of the oscillator up to 4.4 GHz.

The other NanoVNA units I mentioned, including my NanoVNA-F, use harmonics for measurements above 600 MHz, limiting their dynamic range. On the NanoVNA-F, the S11 dynamic range is 40 dB and the S21 dynamic range is 60 dB for 600–1,000 MHz. The NanoVNA-V2 Plus 4 claims 70 dB system dynamic range without averaging up to 3 GHz and 80 dB range with 5x averaging.

The NanoVNA-V2 Plus 4’s 4.4 GHz upper frequency makes it ideal for testing 5G filters for the C-band repack. The cost of the NanoVNA-V2 Plus 4 is $129, competitive with the cost of the NanoVNA-F with a similar sized screen. I’ve ordered one through Tindie and hope to have it in time to review in my next column.

As always, I welcome comments and questions. Email me at dlung@transmitter.com. If I’m busy I may not respond right away and if the email gets buried too deep I might miss it. If you don’t get a response within a week or so, email me again.

TV receive antennas are one of the most popular topics based on the number of emails I receive from readers. Many times they will request additional information on antennas I wrote about years ago—the Gray-Hoverman covered in 2008 or the high gain wire rhombic I covered in 2006.

Meanwhile, I often learn new things from readers. Bill Robbins, an over-the-air TV viewer in Florida, was concerned about reception from his antenna setup. I’ve found trying to align or adjust a TV antenna using the “quality” indicator on a TV set or the signal level on a meter is difficult, slow and doesn’t always find the best orientation. A spectrum analyzer is a better choice.

Fortunately, these no longer cost thousands of dollars. I recommended Robbins pick up an Airspy SDR and use its free Spectrum Spy software to look at the spectrum of the incoming signals, aligning the antenna for best level and best flatness (least multipath) on the desired channels. He bought an Airspy R2 and sent me a screenshot of the final result. It looked good. He’s using a Winegard LNA-200 (one I’ve also found to work well) and RG-11 coax from the antenna to his in-home distribution setup. However, I’d never heard of the TV antenna he was using—the HD-Stacker. So when he asked my opinion I looked into it and found it quite interesting.

DIGITENNA AND HD-STACKER

In some markets there are a mix of UHF and VHF stations—mostly high-VHF (7–13)—but post-repack, sometimes low VHF (2–6) as well. Unfortunately, the last time I looked, the most common option for people needing high gain at VHF was a monstrous low-VHF through UHF antenna that was as big as a Volkswagon. You know the ones: They have low VHF elements in the back, followed by high VHF elements, followed by a long UHF section.

The HD-Stacker has elements for low-VHF (Fig. 1), which require 60.3 inch-width but is only 70 inches long compared to monster low-VHF to UHF antennas that are more than twice that length. I didn’t find any gain specifications for the antenna but suspect that gain at VHF and UHF will be comparable to the monster antennas. Denny’s Antenna Service (dennysantennaservice.com) did a comparison of outdoor antennas and found that the HD-Stacker did as well as the huge Winegard HD8200U (Fig. 2) except on some low-UHF channels.

This test was done before the repack as it includes stations above Channel 36. The comparison included the DigiTenna DUV-XF, which performed as well or better than the HD-Stacker except at VHF and high (above Channel 36) UHF. The DigiTenna includes an amplifier with a second input that could be used for a high-gain, high VHF-only antenna to create a stack, although when I was searching for one of these for another reader it looked like VHF-only antennas had been discontinued, at least by the major consumer antenna manufacturers.

The performance of DigiTennas at lower UHF channels should improve a bit as Brad Eckwielen, president of DigiTenna, told me he was modifying the design of the fan dipole-driven element to optimize performance between Channels 14 and 36, ignoring channels above 36. Perhaps more important to viewers requiring a preamplifier in weak signal areas, Eckwielen has modified his amplifier to provide 20 to 30 dB of LTE filtering above Channel 36 (608 MHz).

Most filters now allow through signals up to 698 MHz (Channel 51). This is important as T-Mobile and other carriers build out cell sites in the 600 MHz band. TV tuners, which still cover up to Channel 51 (if not Channel 69) will be susceptible to overload if a preamplifier is used. See digitenna.com/Products for more information on the preamplifier.

NEW NANOVNA DESIGN

In my January column (“Checking Out TV Antennas With a $130 VNA”) I used a NanoVNA to check a number of different indoor antennas and noticed the return loss increased at low UHF on most of them. It would be interesting to see what the new DigiTenna-driven element looks like after optimization for lower UHF and I wonder if other manufacturers, like the HD-Stacker, Winegard, Channel Master, Antennas Direct, etc., will be modifying their designs to improve performance in the truncated UHF band.

Since the VNA article, I’ve learned more about the different varieties of NanoVNA. Some new versions have appeared, software has improved, but unfortunately, getting products from China has become much more difficult with the drastic drop in flights between the United States and China due to COVID-19. Products ordered from China are usually shipped by ePacket or similar service that depends on space available on flights to the United States and a hand-off to the U.S Post Office for delivery. Out of the two products I ordered this year, one eventually made it to me in about two months. The other was returned to the sender after a bit over two months, apparently because the shipper couldn’t find any flights. When ordering gadgets from China, use DHL, UPS or some other service with its own aircraft.

The NanoVNA unit I’m recommending now is the one with the 4.3-inch LCD I showed in the January column. This turned out to be a NanoVNA-F. Details on the design of the unit are available at https://github.com/flyoob/NanoVNA-F. Note that the latest version has 0 dBm output at the generator fundamental frequency (up to 300 MHz) and will operate up to the fifth harmonic allowing measurements to 1.5 GHz.

In the 10 kHz to 300 MHz band its dynamic range is 70 dB dropping to 60 dB in the 300 MHz to 900 MHz band. I had no problem upgrading the firmware in my 2019 unit to the latest firmware—it is as simple as copying a file to a flash drive—but I didn’t get the benefit of the extra output (older units were –13 dBm) and the improved RF bridge in the latest hardware version.

If you want the latest hardware, order from www.aliexpress.com at the DeepElec store and use DHL shipping. If you want to order from a U.S. source such as Amazon or eBay, check out the version in the DeepElec store—images, specs, etc.—and make sure the one you are ordering specifies the same version, has the same specs, and looks the same as the DeepElec NanoVNA-F. The price should also be higher, assuming people are buying these units from DeepElec and not importing some no-name clone that may not offer the same performance.

I recently learned of a new NanoVNA, the NanoVNA-V2. This unit has a smaller screen, no battery and no case, as can be seen from the official website at https://nanorfe.com/nanovna-v2.html and also at https://groups.io/g/NanoVNA-V2. The websites claim operation up to 3 GHz with 40 dB dynamic range at that frequency. The website www.tindie.com/products/hcxqsgroup/nanovna-v2/ is selling official units starting at $59.95 as of this writing. A calibration kit and acrylic case are available at extra cost. Special software for Window, Mac OS and Linux is available for the NanoVNA-V2 at https://github.com/nanovna/NanoVNA-QT/releases.

The latest version of NanoVNA-Saver also runs on Mac OS, Windows or Linux and will work with most of the NanoVNA hardware, including the NanoVNA-F and the NanoVNA-V2. This is the software I used in the January article. The software is updated regularly and remains my choice for driving the NanoVNA from a laptop or PC.

If you don’t want to bother installing software to run the NanoVNA, there is now a web-based client available that works with the NanoVNA-F and some other units. Cho45’s software, available at https://github.com/cho45/NanoVNA-Web-Client, should work on Mac OS, Windows, Linux or Android. I’ve tested it with the NanoVNA-F on Windows, Linux and Android and it worked fine, with surprising functionality.

Fig. 3 is a shot of the web client connected to my NanoVNA-F displaying the frequency response of a Channel Master LTE filter. Due to COVID-19 and travel restrictions I’ve been unable to get back to Los Angeles where most of my RF adapters are stored, so the accuracy of this plot may not be the best because it was done without using 50 to 75 ohm minimum loss pads or transformers. Follow the instructions on the Web-Client web page. You may have to modify settings in Chrome or, if using Linux, make sure your user is in the same serial device group as the NanoVNA. I had to add myself to the “uucp” group to get it to work.

You can learn more about the NanoV-NA in my column in the IEEE Broadcast Technology Society magazine for March, 2020 (you can search for it on https://resourcecenter.bts.ieee.org). It is free to IEEE BTS members. In the article I show a block diagram of the unit and describe how it works. A key component is a Texas Instruments digital FM stereo matrix decoder!

A final note—I’ve finally gotten around to updating my transmitter.com website. It is still a work in progress, but there are now links on the homepage to folders with some of the tools I’ve created and mentioned in previous articles and what I hope to make a monthly feature—highlighting an article on the website from TV Technology that I wrote more than 20 years ago. The current one is a build it yourself frequency standard and calibrator from March 1994. WWV and WWVH fortunately received funding to continue operating so the device can be built and will still work 26 years later!

As always, I welcome your comments and questions. Let me know what I’ve missed! Email me at dlung@transmitter.com.

In my column last month (“Get Ready for ATSC 3.0, But Don’t Ignore 1.0”), I compared ATSC 1.0 and ATSC 3.0 reception. While it is being rolled out, ATSC 3.0 is likely to require similar antennas to those currently used for ATSC 1.0 since signal-to-noise requirements are likely to be the same. I received some email from readers who complained that even though they had sufficient signal strength for ATSC 1.0 reception, multipath was a problem, and they were looking to ATSC 3.0 to fix that. In this column, I’ll show how ATSC 3.0 handles multipath differently than ATSC 1.0 and also look at some other features in ATSC 3.0 that broadcasters can use to improve reception.

MULTIPATH AND SPEEDING TRAINS

Multipath occurs when multiple copies of the same signal reach the receiver. These copies could be from other transmitters in a distributed transmission system (DTS) or, more likely today, from reflections from other objects. These objects include stationary objects like buildings and bridges and moving objects like trucks and airplanes. The impact of multipath on reception depends on the difference in time and the difference in signal level between the signals. 

ATSC 1.0 is a single carrier transmission system. One 8VSB carrier has to carry the ATSC data rate of 19.392 Mbps. Multipath is visible on a spectrum analyzer as ripple (Fig. 1) in the 8VSB spectrum. By measuring the ripple it is possible to determine the time difference between the signals creating the multipath. (See my Jan. 1, 2000 article “Comparing 8VSB and COFDM for DTV Broadcasting” for details on how to do this. Fig. 1 is missing, but is the same as Fig. 1 here.)

ATSC 1.0 receivers deal with multipath using adaptive equalizers. In the simplest sense, an adaptive equalizer digitally stores copies of the incoming signal and shifts them in time to cancel out the multipath. As a result, the range of multipath delays and signal levels an ATSC 1.0 receiver can handle is dependent on how much the receiver manufacturer is willing to spend on the equalizer. The “coupon-eligible” DTV converter boxes sold during the analog-to-digital transition had to meet certain standards, but those do not apply to TV sets sold today. This variability in receiver performance makes ATSC 1.0 DTS design difficult. 

With ATSC 3.0’s OFDM, multipath performance is controlled by the broadcaster. In OFDM, the data is divided among thousands of carriers so each carrier has to carry a much smaller amount of data. Multipath appears as interference between OFDM symbols; ATSC 3.0 handles multipath by inserting a guard interval between symbols. The guard interval (GI) is created in the time domain by taking samples belonging to the last part of the OFDM symbol and prepending them as a cyclic prefix to the original symbol. 

This extra information allows the receiver to fill in the information lost due to multipath. ATSC 3.0 offers 12 selections of GI sample size. The relationship between the number of samples and the allowable time difference between multipath signals depends on the number of carriers as explained in my Jan. 1, 2000, article. 

For a detailed explanation the cyclic prefix and how it works, look up “The Cyclic Prefix for OFDM” at dspillustrations.com. This website also offers a digital communications tutorial using a computer sound card for hands-on experience. Fig. 2, which shows how the cyclic prefix is generated, is from this website. 

The use of OFDM in ATSC 3.0 doesn’t eliminate the need for an equalizer to remove distortion in the signal caused by multipath or frequency response variations in the receive system itself. The ATSC 3.0 standard has pilot carriers with known characteristics that can be inserted at regular and scattered intervals in frequency and time to make equalization easier. More pilot carriers will make it easier to lock on the channel with varying multipath. 

Adding guard interval reduces usable symbol time and adding pilots reduces the number of carriers available for data. The optimum guard interval depends on the maximum multipath time difference. Testing of ATSC-MH (mobile-handheld) in the San Francisco area found a very long echo from the San Francisco-Oakland Bay Bridge caused reception problems in some areas—a long guard interval would fix that. When multiple transmitters are used in a DTS, the spacing of the transmitters and the signal overlap will determine the guard interval required. The ONEMedia App (see details later) will provide the guard “distance” for a given system configuration. 

There is another element to multipath, which I did not mention earlier—Doppler. Doppler is the change in frequency as an object moves towards or away an observer, (as with a train whistle increasing in pitch as it approaches and decreasing as it moves away). 8VSB performance with Doppler was poor and varied by receiver, resulting in some viewers losing reception due to reflections from planes passing overhead.

Reflections with Doppler can cause loss of an OFDM signal as well, but the standard offers options to deal with it. Earlier, I mentioned OFDM divides the data among many carriers. The FFT size options are 8K, 16K and 32K, roughly corresponding to 6,900, 13,800 or 27,600 carriers. A larger FFT size is more efficient, but because the carriers are spaced closer together it will be more susceptible to Doppler. An 8K FFT is most robust, allowing mobile reception at any terrestrial speed likely to be found in private or public transportation, at least in the United States.

The impact of reflections, either as static multipath or as Doppler, once outside the range of the FFT or guard interval to handle it, is the same as noise. As a result, a robust signal with a lower SNR (signal-to-noise ratio) requirement will be less affected by multipath or Doppler. One way to take advantage of this is to use an FFT of 16K with LDM. While the robust LDM layer will experience more Doppler interference with the 16K FFT, if the required SNR is much lower, it can still work in many mobile environments while preserving the benefit of a 16K FFT for the enhanced layer.

IMPULSE NOISE

One problem that has plagued ATSC 1.0 reception, especially at VHF, is impulse noise. ATSC 1.0 has a data interleaver to spread data over time to reduce the impact of brief signal loss, but that time is limited to a small fraction of a second. ATSC 3.0 has three time interleaver modes: None, Convolutional Time Interleaver (CTI) and Hybrid Time Interleaver (HTI). Extended Time Interleaving (ETI) is available for physical layer pipes (PLPs) using QPSK. 

The length of the interleaving depends on how the ATSC 3.0 PLP is configured, and can be much larger than that available with ATSC 1.0. With so many options, it will likely take extensive field-testing at VHF (perhaps including low VHF) to determine what configurations work best. Using CTI and HTI should not impact data capacity, but the longer the time interleaving, the greater the latency. 

ATSC 3.0 also includes a frequency interleaver, which would aid in reception in the event a single carrier or group of carriers was interfered with or otherwise lost. 

To learn more about the options available in ATSC 3.0, see ATSC Recommended Practice A/327, “Guidelines for the Physical Layer Protocol,” available from the ATSC web page under “Recommended Practices.” To play around with the options, ONE Media (the Sinclair company focused on ATSC 3.0), has created the app “NextGen TV Calculator” to determine channel capacity and performance of an ATSC 3.0 signal with different configurations, including guard interval. Visit onemediallc.com for IoS and Android download links. Fig. 3 shows a sample of the input and output from the ONE Media app on Android. The input and output data extends above and below what’s shown in the screenshot. The output, for example, includes final required SNR under Gauss, Rice and Rayleigh channels for the configured input.

I welcome your comments and questions on ATSC 1.0, ATSC 3.0 or broadcast RF technology in general. Email me at dlung@transmitter.com. 

COVID-19 has slowed, but not stopped, the transition to ATSC 3.0. Work continues in the ATSC to refine the standard and stations and corporations like Public Media Group and broadcaster groups like Pearl TV are readying plans to deploy. “Safe-at-home” regulations have led to huge increases in ratings for local TV stations, particularly news. People are (re)discovering broadcast TV. 

I’d like to make the argument that while we’re building out ATSC 3.0, viewers shouldn’t ignore ATSC 1.0. One thing I’m finding when I talk to people about ATSC 3.0 (Pearl and ATSC have done a good job marketing it as “NextGen TV”), is that there is much hope (or, for some, fear) that ATSC 3.0 will make broadcast TV programming available for free to everyone who buys a small antenna. They might even get free 4K UHD. Ads like the one in Fig. 1 show how crazy some of the claims are. Search Google for “4K UHD Antenna” (without quotes) and see what comes up.  

OVER-THE-AIR TV STREAMING GATEWAY

What’s wrong with this picture? While over-the-air 4K UHD isn’t available now except for a few test broadcasts, and that magic antenna won’t bring in signals from 980 miles away, for most people it isn’t that hard to get the major networks in full HD and a variety of specialty channels in SD right now with ATSC 1.0. There are even ways to stream it from an antenna to an app on your TV or portable device or record it for later viewing. 

If you don’t want to bother with antennas for every device, putting the broadcast signals on your home network will allow viewing on any connected device. The antenna and box can also be placed in a location where the signals are best, even if the TV isn’t there. 

The HD Homerun units from Silicon Dust have been around a while and can be equipped with up to four tuners for simultaneous reception of different channels on different devices. Prices start at $99 for two tuners and go up from there for more tuners, transcoding and DVR capability. Channel Master’s Stream+ has two tuners and includes Google Play for streaming services for $99. Also for $99 is Hauppauge’s CordCutter TV, which includes two tuners and transcodes broadcast MPEG-2 video to H.264 at lower bitrate for less strain on the home network; however it doesn’t have a built-in DVR option. All of these devices should work with Android, FireTV, Windows, Apple TV or iOS apps. 

These devices and TV sets will need an antenna. For many people a simple antenna like the Onn ONA19CH002 I found at Walmart for under $20 will bring in most local channels with a little effort. People who’ve always had their TV set hooked to a cable connection in the wall often don’t realize this. While a proper antenna is best, for a quick check in strong signal areas take an unfolded paper clip (one without plastic coating); push one end into the antenna connector on the back of a TV set; select “antenna” and rescan. You may be surprised how many stations you get. 

3.0 VS. 1.0 RECEPTION REQUIREMENTS

What does a TV station’s coverage look like if we assume an indoor antenna? Fig. 2 shows a plot of predicted signal strength for WRC-TV in Washington, D.C. The green area is where the field strength is predicted to be 88 dBµV/m or stronger, at least 40 dB stronger than the FCC required “community grade” signal for a UHF DTV station. This extra margin will, in many cases, offset signal loss from walls and signals received as a reflection off other buildings. This coverage prediction doesn’t take into account that buildings and foliage can add loss, but on average a simple indoor antenna should work for most people in the green area. Reception outside the green area may require a bit more fiddling with the antenna or moving it to a higher location in the house or even outside.  

Now lets see what indoor coverage would look like if WRC-TV converts to ATSC 3.0 using the same power and antenna. The most likely coverage scenario while stations are broadcasting in both ATSC 1.0 and ATSC 3.0 will still be the green area in Fig. 2. Why no difference? The required signal-to-noise ratio (SNR) for the ATSC 3.0 signal is likely to be the same (15 dB) as that for ATSC 1.0, or even a bit worse. The SNR won’t be any better because bits (data rate) would have to be sacrificed to make the signal more robust. 

This could be done if the ATSC 3.0 station were carrying the same content as one 1.0 station, but initially there will be far fewer 3.0 stations than 1.0 stations and those 3.0 stations will likely be carrying programming from multiple 1.0 stations. I covered that scenario years ago in my July 2015 column “Getting Ready for ATSC 3.0.” Even with the greater efficiency of HEVC video coding, bits are going to be precious. ATSC 3.0 will have some advantage in areas with multipath making antenna placement less critical and reception somewhat easier.

There will be trade offs between the number of stations available on ATSC 3.0, the resolution of their video (4K, 1080p, 720p, HDR?) and the robustness of the signal. Some broadcasters may decide to up the data rate even if it results in less coverage than ATSC 1.0. 

What’s the lesson for viewers? If you want to receive high-resolution ATSC 3.0 in the future, check 1.0 reception now.  

One advantage ATSC 3.0 offers broadcasters is the ability to protect content, just as cable companies and streaming services do now. Premium services can be offered for a price (a subscription fee or registration) and recording blocked. This will ensure quality content is still available over the air, but it also means that with ATSC 3.0’s security features we’ll likely lose the ability to record some (most?) shows over the air, store them forever on a hard drive or DVD and watch them later on any device. With ATSC 1.0, there are no technical limits on what a person can do with the content recorded from over the air broadcasts, even in full HD. 

The lack of a robust ATSC 3.0 signal for early adopters may be disappointing, but the standard does offer techniques for more robust coverage as more stations convert to 3.0. One is to add transmitters in a distributed transmission system (DTS)—also referred to as “single frequency networks”—which increases signal strength to viewers making reception easier without the need to reduce data rates (expanding the green area in Fig. 2 to the entire market). However, building out a DTS is expensive. Other methods steal some data capacity (TDM or FDM) or power (LDM) from the less robust stream to provide a low bit rate robust stream. See sidebar for details on how these techniques work. 

When viewers ask me for help receiving ATSC 1.0, they usually have some signal, but it has artifacts and dropouts. Adding robustness by either increasing signal strength or reducing the required SNR, as described in the sidebar, would provide a great improvement in reception. The blue area in Fig. 2 shows the increase in indoor service area achieved by reducing the required SNR to 5 dB (at lower bit rate and resolution), compared to the 15 dB SNR scenario. Will broadcasters be able to spare the capacity to transmit a robust stream? How long will it take to find the resources to build out the DTS required to increase the signal level delivered to viewers over a wide area? 

While I expect long time readers are already using antennas to pick up ATSC 1.0 broadcasts, if you haven’t tried receiving ATSC 1.0 give it a try; you’ll be prepared when 3.0 makes it to your market and into your TV.  Let me know how it works out! My email is dlung@transmitter.com.  

Vector network analyzers (VNAs) are amazing tools that not only let you check an antenna’s VSWR (and return loss) over frequency, but also display the complex impedance of the antenna. Some can be used as a time domain reflectometer (TDR) to determine the length of a coax or transmission line, or to determine the distance to the fault in a line. Two port VNAs can display filter response and return loss.

AFFORDABLE VECTOR NETWORK ANALYZERS

Such versatile tools have been quite expensive. Even a basic analyzer from Copper Mountain Technologies, one of the most popular brands of VNA, costs well over $2,500 and that’s before adding a calibration kit. I was surprised when I was checking out WVIT’s new post-repack transmission facility in Hartford, Conn., and consulting engineer Joe DiMaggio told me about a VNA he found that cost about $350.

He compared his miniVNA with a professional VNA and found it surprisingly accurate.

I immediately ordered a miniVNA Tiny Plus2 similar to his from China. The unit arrived in a nice case with cables and SMA calibration kit. I downloaded the required Java-based software from http://vnaj.dl2sba.com. This VNA covers 1 MHz to 3 GHz and the software offers a number of options for typical one and two port VNA measurements for checking antennas, filters, cable loss, amplifiers, etc. The TDR function is limited to determining the length of a coaxial line. The miniVNA Tiny Plus2 kit was a bit big, however, for packing in my travel kit.

While searching for software for the miniVNA I came across the NanoVNA analyzer (Fig. 1). The original units have a 2.8-inch LCD screen and are about 54x85.5x11mm in size. Frequency range is 50 kHz to 900 MHz. I bought one for $53 from Amazon (shipped from China). These VNAs use an open source hardware design and quality varies greatly. Some units don’t even shield the RF components, and while most come in a plastic box with the calibration kit and cables, the VNA itself is just a stack of the metal back plate, circuit board and LCD with the sides open. Based on reviews I’ve seen online, the cheap units that have a replica of the Copper Mountain lizard logo on them are the worst. Amazon prices have gone up due to tariffs, but most are still under $75.

While searching for a case I found an improved version of the NanoVNA on eBay. This unit has a 4.3-inch LCD display, full metal case, and claims a 1 GHz upper frequency limit. Search eBay for “NanoVNA VNA HF VHF UHF Vector Network Antenna Analyzer + 4.3 LCD + Metal Case” to see the offerings. The price is around $125, direct from China. I recommend choosing a top-rated seller. The 4.3-inch NanoVNA, along with the nanovna-saver software (https://github.com/mihtjel/nanovna-saver) is what I used in this article.

In addition to the measurements available in the miniVNA’s software, nanovna-saver also includes an X-Y TDR display that can show discontinuities in the middle of a cable as well as cable length. The program is Python-based and available as a binary file (currently nanovna-saverv0.2.0. exe) for Windows and a simple installer script for Linux. It works with both the 2.8-inch and 4.3-inch versions of the NanoVNA. Since the NanoVNA includes a display, a computer and software isn’t required, but will provide additional measurement options (like TDR) and segmented sweeps (for greater resolution) and the ability to save parameter data in standard format (s1p, s2p) and plot graphs.

Before you get too excited about these low-cost VNAs, there are some significant limitations. The maximum output power is around –9 dBm for the NanoVNA and –6 dBm for the miniVNA. Available software doesn’t appear to have an option to eliminate interference from the strong signals likely to be present at a broadcast antenna site. I suspect they wouldn’t last long connected to an 8-inch transmission line feeding an antenna on a shared tower. The accuracy will depend on the accuracy of the open, short and load used to calibrate the VNA.

Even with these limitations, I find the NanoVNA useful and worth packing in my travel kit. Fig. 1 shows a test setup I used to measure a Channel Master LTE filter; Fig. 2 shows the results. For this measurement I used minimum loss 50 ohm to 75 ohm pads to present the proper impedance to the filter and calibrated the VNA at 75 ohms with a homemade 75 ohm cal-kit. As you can see, the drop off above 698 MHz is quite steep, but we’ll need a new version that cuts off frequencies above 608 MHz once the incentive auction repack is finished next year as I’m already seeing strong cellular signals popping up in the new 600 MHz wireless band.

TESTING INDOOR ANTENNAS

I tested a few antennas using the NanoVNA calibrated with my 75-ohm cal-kit on the output of the RG-6 coax to the antenna. For antennas, the 50 to 75 ohm pad is not necessary if VNA is calibrated using the 75-ohm cal-kit. I found my vintage Mohu Leaf, which has traveled in my suitcase with cables of various sorts for more than five years, apparently now has some broken connections as its return loss was a flat 2 dB across the 470–608 MHz band.

I ordered a new Mohu Leaf 30 and will report on how it works. I tested a gigantic Mohu Leaf Glide 65 (without preamp) designed for VHF and UHF and found, as expected, it had decent return loss (Fig. 3) across the repacked UHF band. The Winegard Freevision FV30-HD had good return loss in the mid-band channels, but return loss increased at the lower UHF channels. Fig. 4 shows the Winegard antenna after I shortened the balun leads. I found that with the full-length leads, the performance was worse. Without the VNA, I would have never noticed this.

I needed a thin antenna to replace the Leaf while waiting for the new one to arrive. I found an Onn ONA19CH002 Indoor TV Antenna for only $16.88 at Walmart. The antenna is transparent so the antenna element is clearly visible. It worked well in the four cities I tested it in (Miami and Tampa, Fla., Hagerstown, Md. and Los Angeles).

Unfortunately the thin coax cable is permanently attached to the antenna so I was only able to measure the return loss with the cable included. Fig. 5 shows the result using the NanoVNA calibrated with my 75-ohm cal-kit. The sine wave-like variations in the return loss and VSWR plots are due to coax cable and return loss overall is reduced by losses in the cable.

DIGITENNA ANTENNAS

I mentioned the DigiTenna a year ago when describing the setup Meintel Sgrignoli Wallace (MSW) uses for field measurements, (Indoor Antennas, Field Measurements Revisited, January 2019). While I was in Chicago in November for some signal testing DigiTenna owner Brad Eckwielen visited WMAQ-TV and showed us his range of antennas. I had my NanoVNA with me so we also did a number of measurements on the antenna.

I was impressed with the performance of the antennas, which are much simpler than many of the common antenna designs. The key element in his antenna is a driven element that looks like a solid bowtie, but somewhat bigger than those seen on UHF antennas.

Eckwielen put a lot of effort into obtaining a good match from the 75-ohm coax to the antenna, and has modified the shape of the element to provide good results on both UHF and VHF. The DT-31 element I tested is the current design and optimized for the full 470–698 MHz UHF band. As you can see in Fig. 6, the return loss at the low end of the UHF band isn’t as good as at Channel 36. Newer DigiTennas will be designed for better return loss over the new, narrower, 470–608 MHz band.

Higher gain versions of the antenna add a corner reflector for UHF and a reflector element for VHF as well as directors. A version with a low-noise preamplifier built into the matching assembly at the feed point is available for very weak signal areas. One of the engineers at WMAQ-TV plans to compare a mid-range DigiTenna with his Winegard HD8200U monster antenna. If he shares the results, I’ll share them in a future column.

DigiTennas are primarily available through authorized distributors/installers, but TV station engineers can contact him directly. One distributor is a1 Components (www.a1components.com). Because these antennas are made in Wisconsin, not in China, don’t be surprised at the price—often more than double that of Chinese-made antennas.

RESCA REVISITED

A reader pointed out that I missed a rescan tip in my last column (Phase 4 and More, Surviving the Repack, August 2019). The direct-tune (RF Channel. Program Number) method won’t work on many sets if the channel is already in the receiver’s memory. For some receivers, the memory can also prevent the tuner from finding changed channels.

The solution for both these problems is simple. Clear the TV set’s memory by doing a scan with no antenna selected; verify no channels are listed; then scan (or direct-tune) to get the updated channels.

As always, I welcome your comments and questions atdlung@transmitter.com. Let me know if you are interested in VHF impedance plots of these antennas. Responses may be delayed if I’m busy, bug me again if you don’t get an answer in a week or two.

The deadline for Phase 4 of channel repacking in the FCC’s incentive auction has passed and it appears to have been the most challenging one to date. This month I’ll outline some of the Phase 4 experiences and lessons for future transitions, and provide some tips on helping viewers with rescan and reception issues.

I was on the 90th floor of One World Trade Center in New York with the transmitters on Aug. 1 when many stations in Hartford, Conn., New York, Philadelphia and Washington D.C. transitioned to their new channels. The switch took place at 1 p.m., in the middle of the day and not at the 11:59 p.m. Aug. 2 deadline. Boston changed channels at 1:05 p.m. the next day.

Switching channels in the middle of the day has several advantages, the main one being more staff available to help resolve problems or answer viewers’ calls. While the FCC set the phase deadlines on Friday just before midnight, stations can transition anytime during the FCC test period before the deadline on the condition they provide proper public notice and coordinate with other stations.

The Phase 4 deadline was not the trainwreck many feared, but not all stations were able to operate with their final facilities. In at least two markets, New York and Boston, many stations were not able to transition to their final antenna or power because work could not start on the final facilities until the old channels were shutdown. In both cases, however, this had little impact on coverage.

ONE WORLD TRADE CENTER

UHF stations at One World Trade Center were all operating on the upper antenna (RFS PEP40 panel array) on their old channels at reduced power while the RFS combiners (two are necessary to achieve variable polarization) associated with the lower antenna (RFS PEP96L) were tuned to the new channels. You can see a snapshot of the job configuring and tuning the One World Trade Center combiners for the new channels in Fig. 1.

On Aug. 1, One World Trade Center UHF stations switched to the lower antenna and combiner system. For some stations, this was the antenna authorized in their construction permit, but even though they were able to test individually at full power they had to reduce power before all the UHF stations (WCBS-TV, WLIW, WNBC/WNJU, WNYW, WWOR-TV, WPXNTV) could operate on the antenna with a good safety margin. The impact on coverage from use of the One World Trade Center lower antenna and power reduction is minimal, thanks to the overall height of the antenna.

The channel changes occurred on time without incident thanks to the cooperation between all stations involved, including those out-of-market stations receiving interference during testing. Kudos to the tireless work by Joe Giardina and his team at DSI, along with the engineers from RFS, configuring the combiners and Durst Broadcasting’s John Lyons management of the project with what seemed like 24/7 availability.

In Boston, UHF stations on a tower owned by American Tower switched to a shared auxiliary antenna system, which closely matched predicted coverage from the main antenna system now under construction.

An easy way to check whether a station is operating at its final power level on its licensed facilities is to use the LMS search feature under “Technical Data” for the station (https://enterpriseefiling.fcc.gov/dataentry/public/tv/publicSearchLanding.htmlorwww.rabbitears.info).

On www.rabbitears.info, a nonprofit website that tracks broadcast RF developments, “DTV-STA” indicates the station is operating under FCC special temporary authority, usually at reduced power or height. “DTV-LIC” indicates the station is licensed while “DTV-PL” indicates the license is pending. “DTV-CP” indicates the station still has a construction permit for the final facility. For Phase 4 stations, the CP expiration date was Aug. 2, 2019. Stations that were unable to complete construction of their final facilities were allowed a six-month extension of the construction permit to Jan. 29, 2020.

In my last column I described the importance of testing facilities before transitioning. At some of the stations I was working at, this turned out to be a valuable step as problems were discovered (and fixed) prior to the transition that would have caused major problems if they occurred after the switch to the new channels.

In situations where the channel was already in use in the market, the only way extended testing was possible was for the testing station to carry the ASI stream from the current channel occupant during the testing, avoiding any impact to that station’s viewers. Unfortunately, post-transition I saw some problems arise that were not caught during testing. Fortunately, the ones I’m aware of did not take the stations off the air for extended periods of time, but did result in some power reductions and temporary loss of coverage. Extended testing, for as much time as possible, prior to the transition date, should be a priority.

RESCAN REMEDIES

With channel changes comes the need to rescan. What happens, however, if during the first rescan the viewer is unable to receive the channel, perhaps due to the new channel operating at reduced power or height? Here are some tips that may help these viewers.

For technically savvy viewers, some TV sets have a signal quality indicator. If other stations are transmitting from the problem station’s location, optimizing the antenna using this signal meter may allow a rescan to pick up weaker stations. Viewers that are less technically savvy are likely to be confused by this solution.

A simpler option, which can avoid the need for a complete rescan, is to tune the TV set to the RF channel and program number (“Physical Channel” in the Rabbitears listing) of the station. For example, in the case of WRC-TV in Washington, D.C., the RF channel is 34 and the program number for NBC is 3. Punching in 34.3 on a TV set’s remote should take the TV direct to NBC, and, once locked, the displayed channel will change to 4.1.

Channel up to see the other subchannels. If there is no reception, the TV set should stay on 34.3, and the viewer can move the antenna to try to find a location or orientation where the signal can be received. Note this only works in markets where the RF channel and program number combination are not in use as a virtual channel by another station that’s been previously scanned. This should work on most TV sets, but I’d appreciate hearing from readers on the results of using this direct tuning method, noting the make and model of TV if possible.

For many broadcast engineers, www.rabbitears.info is the first stop for information on TV stations. The site provides excellent coverage maps showing contours and field strength as predicted using the Longley- Rice terrain sensitive model. The site has a new feature in beta—the Rabbitears Search Map—available at www.rabbitears.info/searchmap.php. You can enter an address in the box on the lower left of the map, then use the “Move Pushpin to Center of Map View” to put a marker on the exact location, as shown in Fig. 2. An example of the output is shown in Fig. 3.

In markets with stations using mechanical beam tilt on antennas on high mountains, such as Los Angeles, the results from the Rabbitears Search Map will be much more accurate than those from other coverage prediction sites like www.tvfool.com and even the FCC’s www.fcc.gov/media/engineering/dtvmaps. The reason is that many of the antenna patterns stored in the FCC’s database for antennas with mechanical beam tilt are based on the horizontal plane radiation pattern—the power going straight out from the antenna and never hitting the ground. This is why the antenna patterns for Mt. Wilson stations appear to be aimed at Lancaster rather than Los Angeles. Where actual un-tilted antenna pattern is available, Rabbitears uses that pattern rather than the highly distorted horizontal plane antenna pattern, resulting in a much more accurate representation of signal on the ground.

The Rabbitears Search Map should be handy for engineers taking calls from viewers with reception problems as they can enter the address into the map and see what stations the viewer should be able to receive and at what signal strength.

ODDS AND ENDS

Finally this month, I have heard from some sources that Winegard has discontinued or will be discontinuing my favorite indoor/outdoor antenna, the Winegard Freevision FV-30BB. I hope that is not true. The antenna still shows up on Winegard’s website for $39.99 and remains available at some Home Depot stores.

This is the antenna I’ve been using for field strength measurements as it is small, works well on high-VHF, and even does a passable job on low VHF. I was surprised how well it worked picking up WPVI’s Channel 6 signal in Philadelphia during testing there. There are other antennas that have more gain and will do a better job at UHF and VHF, but none I’ve found that are as small as this one—easy to hang on a wall; easy to throw in a car trunk with the mast connected; easy to support on an extendable pole.

One thing I’ve noticed, as have some on www.avsforum.com/forum/25-hdtvtechnical, is that the antenna performs much better than the specifications and patterns from Winegard would indicate. I hope Winegard continues to manufacture it.

As always, I welcome your comments and questions atdlung@transmitter.com. Responses may be delayed if I’m busy, bug me again if you don’t get an answer in a week or two.

For more news and insight on the repack, visit TV Technology'srepack silo.

It has been a few months since my last RF Technology column and a lot has happened since then, including the NAB Show in Las Vegas and the FCC Phase 2 repack deadline. This month I’ll attempt to cover the highlights from these and some more interesting items I discovered along the way.

NAB SHOW

The hot topics for discussion among those interested in RF transmission at the NAB Show were the FCC’s incentive auction repack and ATSC 3.0. The main question about the FCC repack was when it would “go off the rails” after stations failed to meet deadlines and blocked other stations from changing channels.

The predominant opinion was that problems would arise later this year as the gap between the phases shortened. However, while I heard a number of horror stories from installers and manufacturers about stations not being ready, most of the station engineers I talked to felt they would make the upcoming deadlines, even if not with their final facilities.

At the Broadcasting Engineering and Information Technology Conference, I was on the “No More Broadcaster Silos: Lessons from the Repack Phases 1 and 2” panel with John Lyons (Durst), Nick Wymant (RFS) and Stephen Kolvek (Myat), moderated by Josh Gordon. We talked about manufacturers’ challenges in the repack along with tips for stations and I discussed issues with dependencies in the repack with a focus on the Phase 4 repack in the Northeast. FCC shows dependencies for some New York City stations from as far away as Ottawa! More on that later.

ATSC 3.0 was everywhere at the show. All manufacturers I saw selling transmitters in the United States were offering ATSC 3.0 options, more test equipment was available, and while assembling a working ATSC 3.0 facility isn’t simple, there were several demos of working systems including components from various vendors.

DS Broadcast was showing a complete “end-to-end” system that had everything needed to provide an ATSC A/324 STLTP stream to a transmitter and monitor the over-the-air result. ATSC A/324 enables connecting a source to multiple transmitters in a single frequency network. The standard has been widely adopted by transmitter manufacturers and an excellent example of its use was the SFN NAB set up with multiple transmitters from different vendors in the North Hall and LVCC lobby outside Central Hall.

Two other items caught my eye at the show. I described use of the Sixarms drone-based RF measurement system for doing antenna pattern measurements in my column “Verifying TV Facility Coverage” (February 2018). At the NAB Show, Sixarms showed another drone-based system, this one designed for field measurements. It simply goes up and comes down, providing an aerial equivalent of a 30-foot mast. It can take measurements from multiple stations, and is small enough to be easily deployed from a small SUV or even a rental car. This could be an ideal alternative—at significantly lower cost—to a large van with a pneumatic mast or to the simple field measurement system I described previously, although at many times the under-$300 cost of that setup.

There were several options for ATSC 3.0 monitoring at the show, including a notebook-based system from Triveni and the Airwavz Redzone ATSC receiver now available with Windows software that includes the ability to display video.

I had my Redzone receiver with me at the show, but the only software I found for download was an updated version of the API and some simple tools similar to what I previously reviewed. It looks like the Windows software is available if purchased as a complete kit with the Redzone receiver.

Various Triveni packages provide everything needed for a wide range of ATSC 3.0 measurements, but display of RF characteristics will depend on the capability of the dongle or receiver used with it. I was particularly interested in Triveni’s new StreamScope XM Verifier.

I’ve been a fan of Avateq’s monitoring receivers since they introduced their 8VSB receiver several years ago, which provided RF modulation measurements and monitoring/logging capability at a price low enough to install at every transmitter site. Now that transmitters are being deployed with ATSC 3.0 there are very few options for extensive ATSC 3.0 RF modulation measurements. Avateq was showing a range of RF measurement receivers, including the compact AVQ-200 off-air “Signal Inspector,” which seems ideal for fieldwork. The off-air instruments have the capability to display echoes in an ATSC 3 SFN and identify echoes by transmitter ID.

REPACK REVISITED

As I write this, the FCC April 12 Phase 2 deadline has come and gone and the Phase 3 deadline will have passed by the time you read this. The Phase 4 repack, which has an Aug. 2, 2019 deadline, will be one of the most complicated ones in the incentive auction repack as it involves densely packed stations from North Carolina to Maine and west into Ohio and Canada.

One of the challenges will be finding time to test antennas at full power before the deadline. Because this phase involves many stations swapping channels, sometimes in the same market, just firing up on the antenna for testing won’t work.

Stations will have to coordinate times to test with each other, most likely overnight. If the interference isn’t excessive, in between markets for example, both stations may want to agree to accept interference to avoid losing the audience in their core coverage area. If a station’s new channel is on the channel currently occupied by another station in the same market, and if that station can provide the testing station an ASI stream (everything matching what it would be transmitting from its own transmitter), its viewers will only see a momentary interruption as the transmitters are swapped.

Conversations I’ve had with FCC staff indicate that as long as new interference to any existing station is under 2%, no FCC approval or even coordination with impacted stations is required for testing or early transition within the test period, (although it is recommended).

However, if interference to any station exceeds 2% for testing or an early transition, then an engineering STA is required and the other station(s) must agree to accept the interference. If the station that would receive interference goes off the air during the testing, instead of staying on and accepting interference, no engineering STA is required. 

TOOLS FOR REPACK AND FIELD MEASUREMENTS

Keeping track of dependencies for testing post-repack facilities can get complicated, especially when dependencies of dependencies have to be considered. To make them easier to track, I’ve created a simple tool, TVDepTester, available at www.transmitter.com/tools.

For Windows 10 systems, download TVDepTester8.exe and all the .csv data files from the site and put them in the same folder. For any operating system that has Python installed, download TVDepTester8.py and the .csv files (again in the same directory) and run with Python. The “8” is the current version number and will be incremented as I fix bugs and enhance it so by the time you read this, that number may have changed. Run the program and type in the call letters in UPPER CASE and it will search for dependencies through multiple levels. Note that if the program closes without showing results it may be the station is sharing a channel. The FCC lists I’m using only include the host stations.

I’ve been working on making the field measurement program I wrote for the Hauppauge WinTV dualHD USB tuner easier to install and use. Linux is still required, but only the ready-to-use programs, “dvb-tools,” “dvbsnoop” and “w-scan” (for channel scanning) in the Ubuntu repositories are required.

In the www.transmitter.com/tools folder look for “Sample-Test-Script-(Los Angeles).sh” and “channels(Los Angeles sample).conf” for the program and channel listings I used for L.A. measurements. The channels.conf file only needs entries for the stations used in the test script. Edit the list manually to add test channels not found in the scan. Lists from w_scan will need VSB-8 changed to 8VSB. I have written a very simple Python program to tabulate the results from measurements into a single csv file with measurements by time in rows and stations in columns. It’s not quite user-hostile, but email me if you want a copy so I can explain how to use it.

Please contact me or the vendors I’ve mentioned for more information. You can email me atdlung@transmitter.com. 

Readers responded to my article comparing indoor TV antennas—some with questions, some just with comments (Comparing Antennas for Indoor Reception, September 2018). I welcome these as they give me a better understanding of how over-the-air TV works in the real world and the opportunity to share their experiences with other readers.

Reliable VHF reception continues to be a problem and based on recent emails, interference from devices such as LED lamps and even bathroom fans seems to be the most common problem for viewers with indoor antennas.

I also heard from readers having problems with UHF reception. One reader, outside Portland, Ore., was able to get VHF channels but not UHF. There was a small mountain between him and the towers. He’d tried several different rooftop antennas with no luck, but since the performance of consumer TV antennas can vary considerably I could only recommend trying one from a reliable manufacturer that provided real specifications for the antenna (not amplifier) gain.

Another reader who was familiar with propagation of RF signals emailed with his experiences rotating TV antennas to pick up vertically polarized signals. He was able to pick up stations with the vertically polarized receive antenna that could not be received when the TV antenna was horizontally polarized. Polarization shifts on reflection or defraction, so on an obstructed path this was not surprising.

It appears UHF reception isn’t immune to interference. One reader outside Oklahoma City wrote to say sometimes he could get 81 “channels” in a scan but this would drop to 21 “channels” and poor signal at other times. He followed my advice checking for electrical interference but found LTE interference was the real problem. The final solution turned out to be the addition of a “Zenable” LTE filter. Looking at the specs for this filter, I’m surprised it helped as the upper pass frequency of 790 MHz is well above that used for LTE.

For viewers in the United States, the Channel Master LTE filter looks like a better choice, since it rejects signals above 700 MHz. The specs on the Channel Master site are limited (“Frequencies Block 700–2000”). In his September 2016 TV Technology column, Out of Band Interference: Myth or Reality?, Charlie Rhodes measured the performance of that filter, which showed the loss at 740 MHz was 44 dB.

FIELD MEASUREMENT

In December I had a chance to ride along with Gary Sgrignoli and David Lawson from Meintel, Sgrignoli & Wallace LLC (MSW) for some of the 100 measurements they will be doing checking out the performance post-repack facility for San Diego’s NBC O&O KNSD. (These are the precision measurements I mentioned in my October 2018 column, Inexpensive Tools for RF Measurement.) At two of the sites, interference from LTE signals at 740–760 MHz was observed above the KNSD channel 40 signal. (KNSD had not transitioned to channel 17 yet so programming was still on RF Channel 40 with a test pattern without PSIP on RF Channel 17 for the measurements.)

It wasn’t clear interference was occurring to the reception of Channel 40 on the demodulator, but it was quite strong on the Rohde and Schwarz FSH4 analyzer in the van. I noticed the FSH4 has a second IF of 860.8 MHz and a third IF of 54.5 MHz. The relationship of these frequencies to the 740–760 MHz interference and the linear variation of the observed signal at above 633 MHz with attenuation leads me to believe this was filter ingress in the FSH4 analyzer.

This example, and the experience of the reader outside Oklahoma City make me wonder what will happen as LTE signals pop up on what used to be Channels 38 to 51.

I was surprised to see MSW using a consumer DTV antenna rather than a professional or cable headend log-periodic antenna on the test vehicle. Sgrignoli explained that size and weight were an issue and the DigiTenna DT-S (www.digitenna.com), while small and light enough for the telescoping mast and for storage in the van, performed quite well at both UHF and VHF frequencies. My experience is corner reflector/bowtie antennas can equal or beat four-bay bow-tie antennas at UHF. Look for more on the DigiTenna in a future column.

Before starting measurements, the system is calibrated. A calibrated dipole (quite expensive) is mounted in place of the DTV antenna. The measured signal level is used to calculate the field strength of the line-of-sight signal on the channels of interest after applying the dipole calibration factor and accounting for feed line losses. The calibrated dipole is replaced with the DigiTenna and the signal levels measured again to determine the gain of the antenna. These gains are recorded and used to calculate field strength from measured channel power.

This field study includes measurements at 100 sites divided into grids covering different areas. The procedure does not involve taking measurements while driving the van in a line with the mast up or taking a cluster of measurements around each location. This approach decreases the time required to measure the signal at each site and as a result increases the number of sites that can be measured.

One disadvantage of the van antenna setup was that it was not possible to switch polarization, or even mount the antenna on the mast vertically polarized. That didn’t stop us from doing a test at one site surrounded by hills where KNSD was very weak. Holding the DigiTenna about 12 inches above the ground with the elements vertical brought the KNSD signal out of the noise, not enough for reception at this height, but I suspect it would have worked at 30 feet. On Channel 17 KNSD is elliptically polarized with 50 percent of horizontally polarized ERP at vertical.

ACCURATE TESTING

Little did I realize that soon after my last column on simple field measurements was published, I’d have an experience that showed the real importance of doing them as soon as possible after an antenna is ready to radiate.

Measurements the day after a post-repack antenna was put on the air didn’t look right. These were done using the Winegard Freevision FVHD30, a 12-foot painter’s pole, the Airspy SDR with Spectrum Spy and a Hauppauge WinTV dualHD tuner with LinuxTV DVB utilities to obtain signal level in dBm. I didn’t have a precision dipole for calibration, but was able to come up with a rough antenna factor to add to the dBm to dBμV/m at 75 ohm conversion factor of +108.8 by comparing the signal levels from stations on nearby channels transmitting from the same site. Since I was interested in differences more than precise field strength, this was sufficient.

Comparing the measurements to predicted values with the transmit antenna oriented as authorized and with the antenna rotated 180 degrees provided a strong indication the antenna pattern was 180 degrees off, even though the antenna was installed correctly. The manufacturer confirmed there was an error in marking the orientation and has taken responsibility for fixing it. During the transition the station helped hundreds of people rescan to get the signal and in the few cases where there were problems viewers got good reception after tweaking their antennas so it wasn’t obvious there was an antenna issue.

Without the measurements, how long it would have taken the station to determine its signal was several dB weaker than it should have been over the most populated part of the market? Reimbursement for field measurement of the post-repack signal is allowed on FCC Form 399. It is well worth the effort, just in case. I’ve come up with some scripts that make taking channel power and MER measurements from the WinTV dualHD tuner easier. Let me know if you’re interested and I can provide the code and instructions.

As always, your comments and questions are welcome. Email me atdlung@transmitter.com.

As the Nov. 30, 2018 deadline for stations assigned to Phase 1 of the FCC’s Incentive Auction approaches and stations complete plans for the transition to their new channels, I thought other broadcasters and viewers may be interested in the signal levels I’ve been using to compare coverage from different facilities and optimize antenna designs.

During the transition, many stations will be forced to use auxiliary facilities with reduced ERP, lower height or both, which will impact their coverage while their main antenna is replaced with one for the new channel.

I’ve been working on methods for mapping the coverage loss from auxiliary facilities. I’ll describe one of them here.

REQUIRED SIGNAL LEVELS FOR RELIABLE RECEPTION

Outdoor antennas are now a rare sight compared to 50 years ago, although indications are that interest in them is increasing. For most over-the-air TV viewers in and around urban areas, indoor antennas are more popular.

Some studies have been done to determine the field strengths required for indoor reception. One I’ve relied on was presented several years ago based on field measurements by consulting firm Meintel, Sgrignoli & Wallace (MSW). It showed a field strength of 75.5 dBμV/m, on average, was needed for UHF TV indoor reception.

I use that number in my coverage comparisons, but also check coverage at a higher field strength, 88 dBμV/m, for what I call “easy indoor” reception. An “easy indoor” level means the viewer doesn’t have to spend a lot of time optimizing the antenna location or orientation in order to be able to receive the station. This number provides over 10 dB extra margin compared to the MSW findings and is 40 dB greater than the level required for FCC “Community Grade” DTV coverage.

I use a field strength halfway between the 48 dBμV/m FCC Community Grade level and the 88 dBμV/m “easy indoor” level for what could be called “easy outdoor” or perhaps “indoor with effort” coverage. This signal level takes into account the loss from outdoor antennas lower than 30 feet used in the FCC planning factors, and allows for some loss for antennas installed in attics or sub-optimum locations. It can also work for indoor reception if the antenna is in a window facing the right direction and high enough to clear nearby obstacles outdoors.

While these numbers were originally designed for UHF, I’ve been using them for high-VHF coverage as well. Even though the FCC service contour for high-VHF uses a signal level 5 dB lower than that for UHF, VHF reception is usually more challenging, especially for indoor reception, due to RF noise in the house and lower antenna gain.

“Channel 48 Main Coverage Thresholds” (Fig. 1) shows Washington D.C.’s WRC-TV main transmitter facility coverage plotted with these thresholds. Green areas are “easy indoor,” above 88 dBμV/m. Yellow-green areas extend indoor coverage to the 75.5 dBμV/m field strength. The blue areas are those where the predicted field strength is between 68 and 75.5 dBμV/m. Finally, the purple areas extend coverage to the FCC noise limited threshold. Cells with no service due to signal level aren’t shaded and cells with interference (there are 33 of them) are red. This map was created using the “coverpts.shp” files from TVStudy and the open source QGIS GIS.

A simpler way to find a station’s predicted field strength at a location is to use the FCC’s excellent DTV Reception Maps at www.fcc.gov/media/engineering/dtvmaps. Enter a zip code or more precise location and click on the station’s call sign for the predicted field strength from that station. This page only displays the facilities currently on the air.

To see a “rainbow” coverage map for any FCC authorized or applied for facility, use RabbitEars at www.rabbitears.info. Enter the call sign of the station on the first page; scroll down until you see the details on the station; click on “Technical Data” and then “RabbitEars TV Query.” On the new page, scroll down to the facility you want and click on “Longley-Rice Coverage Map” at the bottom of the technical details. RabbitEars is more generous than I am, considering signal levels above 80 dBμV/m “easy indoor” and above 51 dBμV/m “easy outdoor.” (Fig. 2.)

The TV Fool website provides many options for displaying signal power in dBm and noise margin in dB on maps and in tables. Using these values instead of field strength makes it easy to calculate the impact of adding antenna gain or amplification on reception. In many cases, however, adding an amplifier will increase the noise and interference along with the signal level and provide no benefit or even worse reception.

Measuring signal level can be done using any number of signal strength measurement instruments.

A bit of time with your favorite search engine will turn up several options. I’m not going to describe them this month, but will provide a tip on an easy and inexpensive way to measure a TV signal’s power in dBm. The Hauppauge WinTV dualHD USB tuner uses a Silicon Labs Si2157 tuner. The Linux “dvb-fe-tool” will display the signal power in dBm of the station currently tuned to in another program, such as Kaffeine, when run as “dvb-fe-tool-m” in a terminal. The program is available for Ubuntu in the “dvb-tools” package. It is also possible to derive MER (Modulation Error Ratio) from the WinTV dualHD using the “femon” command line program, but I haven’t verified the accuracy.

COVERAGE LOSS FROM TEMPORARY REPACK FACILITIES

Many stations will have to use auxiliary or interim facilities while doing antenna and tower work necessary to switch to their new channels. Stations not changing channels on a tower with stations changing channels are likely to be impacted as well. I’ve been looking at some methods to visualize the impact of the use of these facilities on viewer reception. I recommend stations begin operation on their new channel at full power to insure viewers catch the channel during the market rescan even if this results in coverage loss on the original channel prior to the transition.

The map “Channel 48 Aux Facility Coverage Comparison” (Fig. 3) is an example of a comparison of the main WRCTV facility and the auxiliary WRC-TV facility. Areas where the signal levels from the aux facility are within 6 dB of the main facility or equal to greater than 88 dBμV/m are shown in green.

Areas where the aux facility is over 12 dB weaker than the main facility are shown in gray. In these areas viewers are likely to have more difficulty seeing the aux facility, perhaps requiring an outdoor antenna if they weren’t using one before or upgrading an existing one.

Finally, areas where the main facility has FCC predicted service and the auxiliary facility does not, either due to signal below threshold or interference, are shown in red. For details on how to create such maps, see my article in the fall 2018 edition of IEEE Broadcast Technology or contact me.

If your TV station is operating at reduced power or on an auxiliary antenna during the repack process, I’d be interested in your opinion on whether the thresholds I’ve used for this analysis match your real-world experience. The example I used in IEEE Broadcast Technology had a narrower threshold (+/–3 dB) for equivalent reception since I’ve heard very few viewer complaints when a station has had to go to 50 percent power. Is 6 dB too generous?

As always, your comments and questions are welcome. Email me atdlung@transmitter.com.

For more information on the repack, visit TV Technology's repack silo.

As I write this, the 2018 NAB Show and the ATSC Next Gen TV Conference have come and gone. Since my last column I also had a chance to visit WRAL-TV in Raleigh and see the demonstration of the PyeongChang Olympics broadcast over their ATSC 3.0 station, complete with interactive content.

These events gave me a glimpse of the future of over-the-air TV broadcasting from the perspective of broadcasters, manufacturers and the engineers who created it and are now building that future.

ATSC 3.0 MATURES

Thanks to Pete Sockett and Capitol Broadcasting for inviting me to see the Next Gen TV demonstration in Raleigh at the State Club at North Carolina State University, and allowing me to help with the setup. It was great to see how ATSC 3.0 works in the real world.

WRAL-TV’s ATSC 3.0 transmitter has an ERP of only 40 kW, well below what most broadcasters will eventually use for ATSC 3.0, but even at this power we were able to receive the Olympics UHD programming with a Mohu Leaf antenna attached to a curtain behind the TV.

The more robust stream with WRAL-TV’s HD programming was received reliably around the room on prototype ATSC 3.0 dongles and a standard Windows 10 tablet. For more information and pictures, see www.wraltechwire.com/tag/next-gen-tv/.

The opportunity to see how ATSC 3.0 worked over-the-air in Raleigh and see the options available gave me more confidence broadcasters will be able to successfully roll out this complex standard.

[Read: Verifying TV Facility Coverage]

For a successful rollout, it will be important that station engineers have a chance to play with the technology, try different transmission parameters and explore the options the standard offers for delivering content and emergency information in different ways before the number of viewers increase and business needs limit station engineers’ opportunity to experiment.

At the NAB Show broadcasters were able to see ATSC 3.0 content over low-power transmitters in the exhibit hall and from a transmitter on Black Mountain.

Overall, this year’s demonstrations were similar to those from last year, but more polished, with extended features. For me, it was a sign the ATSC 3.0 landscape is maturing, getting ready for rollout.

One exhibit in the LVCC lobby highlighted all the stations currently on the air with ATSC 3.0 broadcasts — Sinclair’s single frequency network in Baltimore and Washington, the NAB test station in Cleveland, WRAL-TV’s station in Raleigh and new test stations in Phoenix and Dallas. For more on the Phoenix project, see www.pearltv.com/model-market.

Another sign that ATSC 3.0 is maturing was the number of companies showing products for ATSC 3.0 at the NAB Show. Two years ago most transmitter manufacturers promised some upgrade path to ATSC 3.0. Last year, all the ATSC 1.0 transmitter manufacturers I’m aware of offered an ATSC 3.0 exciter option of some sort.

For ATSC 3.0 to succeed, we need to get more ATSC 3.0 stations on the air, even if the number of viewers may be limited.

What was new this year was an increased number of products for receiving and decoding the ATSC 3.0 signals from those transmitters. Other manufacturers offered standalone receiver/decoder solutions.

The price of these receivers — approaching $20,000 or higher depending on the options — seemed high until I thought about what we paid for analog TV monitoring. A proper monitoring setup for an analog TV station around 1990 consisted of a Tektronix 1450 television demodulator (with the TDC downconverter), a VM-700 analyzer and a BTSC audio modulation monitor. It would be tough to put together an ATSC 3.0 monitoring package that cost as much as that setup!

I know many readers are looking for a less expensive way of viewing ATSC 3.0. I had the opportunity to test the Airwavz dongle at the NAB Show. I plugged the dongle into my laptop and was able to view the characteristics of the Black Mountain ATSC 3.0 signal I received in my hotel room. This used an early version of the software that did not allow viewing content on the laptop.

Airwavz said they had tried routing the IP output from the program to the network input of a Sony ATSC 3.0 TV set in the same booth and it was able to decode and display the stream. I’ll have more on this product when I have a chance to upgrade to the latest software and test it in a location with an ATSC 3.0 signal.

In discussions with some manufacturers at the show, it looks like there may be some other ATSC 3.0 dongles appearing at some point in the future. Don’t expect the price to match that of an ATSC 1.0 dongle, but pricing around $250 or less may be possible. Final price and timing for ATSC 3.0 dongles and “converter boxes” (which will likely stream content over an IP connection to a smart TV, tablet or PC running an ATSC 3.0 application) will depend on the availability of lower-cost demodulator chips as well as IP (intellectual property licensing) costs.

WHAT’S NEXT?

At the ATSC Next Gen TV Conference in Washington in May it was clear ATSC 3.0 had the support of broadcasters, consumer electronics manufacturers and even government. Unlike the previous conference, which focused primarily on the technology and the potential of the standard, this year’s conference highlighted real-world applications, some of which are being rolled out now in limited form with ATSC 1.0.

Emergency alerting, with the ability to provide detailed information in the form of maps, videos and text with an ease that would be impossible using cellular messaging is a key feature for governments.

More precise measurement of TV viewing is of interest to advertisers and broadcasters competing with on-line advertising. Both are available now.

The transition to ATSC 3.0 will be complicated, not only for broadcasters but cable companies as well. Cable carriage of ATSC 3.0 content is going to require cooperation between broadcasters and cable companies. I was pleased to hear about the progress made towards this in ATSC TG3/S37, the Specialist Group on Conversion and Redistribution of ATSC 3.0 Service.

For ATSC 3.0 to succeed, we need to get more ATSC 3.0 stations on the air, even if the number of viewers may be limited. In the early days of ATSC 1.0, station engineers had a one-to-one relationship with early adopters of HDTV, sometimes changing settings to help them get reception when one manufacturer’s receiver had a problem with their transport stream.

While all indications are the first-generation ATSC 3.0 receivers are working much better, I expect there will still be a lot of broadcaster-viewer interaction. That’s a key focus of the Phoenix test and essential for a transition to ATSC 3.0 to succeed.

Until full-power stations are willing to put their ATSC 1.0 programming on another station’s signal and switch to ATSC 3.0, finding transition spectrum is going to be difficult. Class A and LPTV stations have a role to play. While the lower ERP (about 4.3 dB less than the WRAL-TV ATSC 3.0 station) may make indoor reception more difficult at higher bit rates, the early adopters of ATSC 3.0 may be willing to make an extra effort to get a decent signal. Setting expectations will be important.

I’m looking forward to seeing more ATSC 3.0 stations on the air, using the Airwavz dongle to see how they work in the real world, and hearing the experiences of engineers putting ATSC 3.0 on the air!

As always, your comments and questions are welcome. Email me atdlung@transmitter.com.

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This month I’ll wrap up coverage of papers at the IEEE Broadcast Symposium as part of a discussion about measuring the coverage of existing or new facilities installed as part of the FCC channel repack.

THE CHALLENGE

Fig. 1: A tower 650 feet away created a 3 dB notch in the antenna pattern.

Click on the Image to Enlarge

Since the beginning of broadcasting, stations and their engineers have looked for ways to verify their signal was actually reaching the audience. Aside from viewer surveys, field measurement of signals on the ground was the only option for these pioneer TV stations.

The size of receive equipment using vacuum tubes and the need to get the antenna high enough to match the outdoor antenna heights used by most viewers at that time mandated specially designed vehicles for these measurements. 

[IEEE Broadcast Symposium Part 1: Repack] 

Anyone who has done field measurements, whether with a sophisticated measurement van or just a field strength meter, a pole and a TV antenna, has seen that the surroundings and antenna height greatly impact the signal level.

The FCC recognized this in the measurement method specified in “Field Strength Measurements,” Section 73.686 of the FCC rules. After describing selection of measurement locations and antenna orientation, it states, “(v) A mobile run of at least 30.5 meters (100 feet) is made, which is centered on the intersection of the radial and the road, and the measured field strength is continuously recorded on a chart recorder over the length of the run.” In an area with power lines, this could be difficult, if not downright dangerous!

I’ve come up with some alternative methods of on-the-ground measurements, which I’ve described in previous columns. One uses an antenna on a 10–12 foot pole able to be stored in a conventional vehicle with measurements taken in a circle with points as close to the same distance from the transmitter site as possible. Due to the location variability noted above and measurement location availability, absolute field strength readings may be unreliable, but at least they can be compared with other stations on nearby channels at the same antenna farm.

Another method is to take hundreds of measurements on the ground using a vehicle with multiple antennas at different orientations designed to be able to grab readings from a dozen stations or more from each of the antennas in less than 10 minutes per location. This is the method used in New York City to check reception from One World Trade Center prior to installation of the master antenna. The main purpose of this study was to verify reception as measured by signal lock and SNR on the different antennas rather than precisely measure received channel power and field strength.

The Cavell-Mertz drone has a custom Tarot-brand frame with six motors and a custom flight controller with inertial sensors.

All of the methods described above show reception only at specific points, which may be affected by structures on the ground. A different approach is to measure the pattern of the antenna, as precisely as possible, then use that as input to propagation software such as the FCC’s TVStudy, V-Soft’s Probe, Progira’s PROGIRA plan, LS Telcom’s CHIRplus or John Magliacane’s free SPLAT to predict signal level at any location. The question then becomes, how do we measure the real antenna pattern once it’s on the tower?

DRONES TO THE RESCUE

Over the past 30 years I’ve worked with engineers from Hammett and Edison to do antenna measurements from both helicopter and fixed wing aircraft. Helicopter measurements allowed the vertical drops needed to measure elevation patterns, but were very expensive and only suitable for locations without flight restrictions, blocking access to areas around the antenna.
Click on the Image to Enlarge

Fixed wing measurements are less expensive but, except for certain mountaintop sites, elevation pattern measurements are difficult if not impossible. 

Unmanned aerial vehicles offer the flight flexibility, high location precision (through GPS-based flight path control) and the ability to operate at heights low enough to measure an antenna’s elevation pattern. Two papers at the IEEE Broadcast Symposium showed how drones could be used to verify antenna performance.

The presentation “Antenna Pattern Measurement With a Drone,” by John Kean at Cavell, Mertz and Associates, provided an excellent overview of the many items that have to be considered. The Cavell-Mertz drone has a custom Tarot-brand frame with six motors and a custom flight controller with inertial sensors for trim, a flux-gate compass for orientation and a differential GPS that provides autonomous flight over a pre-defined path. RF hardware includes a biconical broadband antenna, wireless telemetry and a custom software-defined receiver for measurements. Everything has to be RF shielded to handle the high field strength (over 20 volts/meter) found at tower sites.

Kean cautioned that accurate measurements require flight in the far field of the antenna array. Ground reflections also have to be considered. In his presentation he showed these could cause signal variations from +6 to –25 dB! Careful post-processing of the data is necessary to reduce sampling noise and convert positional information. Kean’s presentation is available to IEEE Broadcast Symposium attendees in the proceedings. Copies may be available through John Kean and Cavell-Mertz at www.cavellmertz.com.

[IEEE Broadcast Symposium Part 2: Antennas] 

Ian Gair, from Sixarms, echoed many of Kean’s cautions in his presentation “Real World Results for a Signal Measurement Drone.” Gair provided a “rule of thumb” for determining the far-field distance for drone measurements: 450 feet for large FM arrays, 1,200 feet for VHF-TV and 1,800 feet for UHF-TV.

Gair provided several examples of antenna issues uncovered with drone measurements. These included an inverted panel in a panel array, a panel oriented incorrectly, antenna tilt due to storm damage and severe elevation pattern distortion caused by incorrect feeder phasing.

Fig. 2: The impact on the antenna pattern of structures at 170 and 540 feet.

The items I found most interesting were the impact of surrounding towers on the antenna pattern. Fig. 1 shows a tower 650 feet away created a 3 dB notch in the antenna pattern. Another example, shown in Fig. 2, shows the impact of structures 170 feet away at 160 degrees and another 540 feet away at 190 degrees. They caused 7 and 4 dB notches, respectively.

For more information on Sixarms drone measurements or to obtain a copy of the presentation, visit the

company’s website at www.sixarms.com.

CHOICES

We’ve become used to thinking of our actual antenna patterns like those plotted on the antenna manufacturers’ datasheets. Traditional ground measurements had so much variability due to obstructions and a limited number of measurement points that even relatively large pattern discrepancies of 3 dB might not be noticed.

The ability to quickly and accurately measure real antenna patterns using drones lets us see the real performance of our antennas and—perhaps more troubling since there may be nothing that can be easily done to fix it—the impact of the surrounding structures on antenna performance.

Signal measurements are a reimbursable expense for stations participating in the FCC incentive auction channel repack and I suspect many broadcasters checked that box on their Form 399. The question now is whether to use a drone to verify antenna performance, use a test vehicle to do traditional on-the-ground radial measurements or a combination of both. What are your station’s plans for post repack measurements?

As always, your comments and questions are welcome. Email me at dlung@transmitter.com.

In my last column I discussed some of the papers presented at the 2017 IEEE Broadcast Symposium related to the FCC TV spectrum repack. This month I’ll look at presentations that covered broadcast TV antennas.

DESIGNING ANTENNAS

If you ever wondered how antenna patterns are created and why certain patterns seem to show up more often, the presentation “Antenna Design for the FCC Repack and Facility Maximization” by Nick Wymant, chief technology officer at Radio Frequency Systems’ Broadcast Division provided the answers. He also showed techniques for modifying antenna patterns to protect other stations when maximizing a station’s coverage. 

Fig. 1: Typical patterns for slot antenna with 1, 2, 3 or 4 slots around

Wymant started by showing how the numbers of slots around a slot antenna’s pipe affect the azimuth pattern. Fig. 1 shows typical patterns for slot antenna with one, two, three or four slots around. Changing the diameter of the pipe will affect the shape of the pattern. For example, reducing the diameter of the pipe used for the three-slot pattern in Fig. 1 will reduce the depth of the nulls until it becomes a rounded triangle. Additional options for modifying the pattern include changing the amount of power going to the slot elements and adding wings or reflectors to the pipe to shape the pattern. The wide variety of patterns available with slots antennas is one of the reasons they are the most popular antenna type for high-power UHF broadcasting.

It is also possible to create custom patterns using panel antennas, which can be useful if they have to operate on more than one channel and support multiple stations. Panel antennas also offer the option of having different electrical or mechanical beam tilt at different azimuths. Wymant showed how panel antenna array patterns can be modified by changing the relative power and/or phase to each face, changing the array orientation and panel positions, or a combination of these methods.

Finding the right antenna pattern isn’t trivial. If options are limited to standard antenna patterns, a pattern that provides interference protection to a station in one direction will likely lead to reduced coverage in directions that don’t need protection. Wymant’s presentation showed the steps in optimizing antenna patterns to meet FCC replication requirements as well as maximizing coverage while still meeting interference protection requirements. The improved optimization method involves using the replication or interference-limited pattern template as a starting point instead of the end goal, and generating one or more customized patterns using powerful electromagnetic simulation software and evaluating to find the best pattern that meets coverage and FCC interference protection requirements. The paper is available to Symposium attendees and may also be available from RFS.

As a side note, I’ve developed software that uses the output of TVStudy to generate a template based on the minimum power reduction necessary on each radial to comply with FCC interference limits as well as maps showing the location and population of cells with interference. Anyone is free to download and use it. See my columns in IEEE Broadcast Technology (available in print and electronically to IEEE BTS members) or contact me for details if interested. Consulting engineer Merrill Weiss has also developed a program he uses—which was mentioned in Wymant’s presentation—that allows interactive modification of a pattern while viewing the amount of interference. This is useful, especially if the interference is present over a wide area, as it allows trading off more power reduction in one direction for greater power (and more interference) in a more desired direction.

WORLDWIDE EXAMPLES OF ANTENNA DESIGN & INSTALLATION

The presentation, “FCC DTV Repack, ATSC3-SFN Considerations & Worldwide Experiences – SFN” by Mark Fehlig and Ben Crease from Jampro Antennas and Alan Dick Broadcast Ltd. focused on the practical side of antenna selection and outlined some items to consider when designing antenna and transmission systems for ATSC 3.0 and single frequency networks. One of the slides shows DVB-T field strength planning requirements for different types of service. For portable outdoor reception, an outdoor field strength at UHF of 78 dBµV/m at 10 meters drops to only 61 dBµV/m at 1.8 meters. For portable indoor reception, an outdoor field strength of 88 dBµV/m at 10 meters will provide only 63 dBµV/m after reducing height to 1.8 meters and allowing for building penetration loss.

The presentation by Mark Fehlig and Ben Crease from Jampro Antennas and Alan Dick Broadcast Ltd. focused on the practical side of antenna selection.

The rest of the presentation shows some actual antenna installations and performance from around the world using broadband slot and panel antennas. The paper is available to Symposium attendees and should also be available from Jampro at the contacts listed on their web site. 

AMT REPACK STRATEGY

Many TV stations being repacked have their antennas on towers owned by American Tower Corporation. If managing the repack is difficult for one station, imagine what it is like managing the repack of multiple stations on one tower. Jim Stenberg, principal engineer, RF Broadcast at American Tower Corporation (ATC), provided a glimpse of that in his presentation “Adventures in FCC repacking! Broadband Antenna Solutions.” Stenberg’s analysis showed that of the 987 Class A and Full Power licensees moving to new channels, 217 of them are on 133 ATC towers.

Stenberg said the FCC’s timeline faces challenges, notably the impact of weather on scheduling and construction delays by non-repack and FM stations. He also said broadcasters should not undervalue their spectrum, as “cord-cutting” is increasing in almost all markets. He was concerned about broadcasters’ lack of interest in interim alternatives while work is being completed and the minimal value placed on auxiliary facilities that could keep a station on the air. 

The presentation used two ATC towers in Atlanta (Chester Avenue and Briarcliff 2) to illustrate ATC’s approach to the repack using broadband antennas. The goal was to minimize repack disruption by maintaining an optimal coverage contour during repack tower work while future-proofing RF systems to incorporate ATSC 3.0 capability into the design. Some key features include use of broadband antenna systems with dual feed lines and dual combiners capable of operating with different horizontal/vertical elliptical polarization ratios, azimuth patterns designed with low ripple and optimized beam tilt and null fill for the market.

I couldn’t quite follow all the moving pieces in the presentation and I’m sure as maximization applications are granted the pieces will move again. I know ATC is working with broadcasters to develop similar plans for other markets. If you weren’t at the Symposium, contact Jim Stenberg or one of other people in the broadcast division at ATC for a copy.

In my next column, I’ll wrap up my coverage of the IEEE Broadcast Symposium with a review of the papers on antenna pattern measurement with drones. With field measurements of signals a reimburable expense for stations replacing antennas as part of the repack, will stations opt for drone measurements rather than conventional ground measurement of signal strength? What are the tradeoffs? As always, your comments and questions are welcome. Email me at dlung@transmitter.com.

In recent years I’ve noticed the IEEE Broadcast Technology Society has added more presentations on the practical aspects of broadcast engineering to its annual Broadcast Symposium. That was evident this year at the symposium in Alexandria, Va., with several presentations to help broadcast engineers deal with designing, permitting and building the new TV broadcast facilities required as a result of the FCC’s incentive auction and repack.

As usual, the symposium also offered ample opportunity for engineers to share their knowledge and experience in the presentations and during the breaks, reception and meals with few of the other distractions of larger conferences.

This month I’ll focus on some of the spectrum repack presentations at the symposium that took place on Tuesday morning. Look for coverage of other topics, including drone antenna measurements, in future columns.

PRACTICAL REPACK

Matt Sanderford, president of the Dallas-based engineering firm Marsand, presented the most comprehensive, unbiased overview I’ve seen of the practical side of converting a TV transmitter site from one channel to another. Anyone who thought this would be a simple process should take a look at Sanderford’s “Practical Implications of the Repack.”

Matt Sanderford

Sanderford covers the process starting with FCC filings, developing a plan to implement the repack and items to consider when designing the repack facility. Choices for items ranging from transmitters (tube or solid state, liquid or air-cooled) to RF switching (motorized switch or patch bay) and even RF reject loads (oil-filled, liquid-cooled, air-cooled, etc.) are compared.

One point I (and I suspect), many other engineers had not realized is that changing channels requires FAA notification even if the tower height or lighting isn’t being changed! Sanderford reminded us that FAA Form 7460-1, line 21, requires listing frequency and power and that power and frequency changes do not need approval and won’t cause delays, just notification and the amended form.

Regarding the choice of transmitter types, Sanderford noted that high-power liquid-cooled solid-state transmitters have around 40 percent system efficiency, compared with around 34 percent for IOT transmitters. While the tube transmitters may have lower capital cost, they require more maintenance and tube replacement cost is high.

I’ve only touched on a few areas in Sanderford’s paper. The presentation is available to IEEE Broadcast Symposium attendees and may also be available from Marsand. Check Marsand’s website, www.marsand.com for contact information.

INTERFERENCE ISSUE

Merrill Weiss, president of Merrill Weiss Group LLC, discussed “Factors Affecting Mask Filter Selection and Channel 14 Operations in the FCC Spectrum Repack.” Weiss’s paper was not available in the proceedings, but I took notes.

A key point of the presentation was that stations should be using eight-pole mask filters rather than six-pole mask filters in their repack facilities. One reason, as Sanderford mentioned in his presentation, is that an eight-pole filter will allow use of the full OFDM bandwidth available with ATSC 3.0. Weiss focused on interference as the primary reason.

S. Merrill Weiss

TV transmitters, whether using 8VSB or OFDM, will have some energy outside the channel due to intermodulation caused by non-linearity in the transmitter. He pointed out that an eight-pole filter provides a 10 dB reduction in energy into adjacent channels.

When a TV station radiates energy into the adjacent channel, it creates interference on the channel that cannot be eliminated by filtering at the receiver. This will be important after the repack as there will be more stations on adjacent channels.

It will become more important after the transition to ATSC 3.0 for stations that want to use high data rate and higher-order modulation to obtain more bandwidth for additional program streams.

Those signals will require a higher signal-to-noise ratio for reception than today’s ATSC 1.0 signals and on-channel noise from adjacent channel stations without sufficient mask filtering could limit the usefulness of the high data-rate modes available in ATSC 3.0. Be a good neighbor, use an eight-pole mask filter!

Weiss also outlined the issues facing stations moving to Channel 14. Typically a 12-pole mask filter is required on Channel 14. Power has to be down more than 100 dB at the channel edge, as there is no guard band between Channel 14 and land-mobile operations in the 450–470 MHz band. Channel 14 construction permits require notification of potentially affected land-mobile licensees. Documentation must be submitted showing no interference to land-mobile radio services before program test authority can start.

This could be a major problem for Channel 14 stations at sites shared with land-mobile operations. Passive intermodulation (PIM) can cause interference even if the Channel 14 transmitter is perfectly clean. Resolving PIM problems can require cleaning up the entire environment at the site—eliminating rusty bolts, corroded connections and other PIM generating components—as well as installing filters on land-mobile filters and transmitters.

Dennis Wallace, a partner and technical consultant with Meintel, Sgrignoli and Wallace LLC (MSW), described a creative solution to WETA’s Channel 14 assignment in Washington D.C. in his presentation “Creative Solutions to Post-Repack Channel Assignment Problems.” MSW analysis showed there were 5,803 land-mobile facilities within 100 km that would be impacted by WETA on Channel 14. WETA’s original Form 399, available using the Public Search feature in the FCC LMS, shows the station determined the cost of a move to Channel 14 at $48,050,047.50 (total), $40 million of which was for land-mobile remediation.

The MSW solution was to find another channel for WETA, but in a market as congested as the northeast it meant other stations had to change channels and a distributed transmission system (DTS) was required to allow Maryland Public TV stations to use one channel to serve an area previously served by multiple channels. The window for filing for channel changes has ended, but I would not be surprised if some stations assigned to Channel 14 have to consider other channels, potentially requiring cooperation from other stations, before the repack is complete.

Wallace’s presentation is available in the proceedings and may be available from MSW. Also see the MSW website, http://mswdtv.com/dtv-repack, for more information on their repack work.

CHANNEL SHARE

Some stations sold their spectrum in the auction and will share a channel with another station. While I’ve described the basic concept and how bandwidth can be allocated in a previous column, I haven’t focused on PSIP.

Dave Catapano

David Catapano, senior vice president of engineering at Triveni Digital, provided an excellent overview of ATSC 1.0 PSIP for those who may have forgotten how it works. He then looked at some of the complications that arise when two stations with different major channel numbers and different program guides share the same multiplex and RF channel.

One of the benefits of the ATSC A/65 PSIP standard is that key data is duplicated in different tables, making it easier for receivers to find a channel, display the proper video and play the proper audio along with the correct program guide and closed-captioning information. The downside is that if data for a program or PSIP element in one table doesn’t match that in another table, the receivers can do unpredictable things. When adding a second channel, with a new major channel number and new site of guides, stations must keep data consistent across tables and avoid mistakes such as duplicating source IDs in the VCT.

Catapano pointed out that it is important to maintain unique PMTs, PIDs and Program Numbers, and EIT/ETT PID/ID pairs. This can get complicated if output from two PSIP generators is being combined at the multiplexer.

Catapano offered some best practices for shared station PSIP, including using Huffman coding to reduce bandwidth, adjusting EIT/ETT table timing (following A/69), optimizing the number of EITs (they may vary with virtual channel) and limit descriptive info to what’s practical. I’ve only covered a small part of Dave Catapano’s presentation, which can be found in the symposium proceedings and should be available from Triveni Digital’s website, www.trivenidigital.com.

As always, your comments and questions are welcome. Email me at dlung@transmitter.com.

For more information on the repack, visit TV Technology's repack silo.

One of the first questions to come up as broadcasters consider their options for auxiliary, interim and final DTV facilities is “How much will this impact my coverage?” The best way to determine this is to do an analysis of the scenarios using the FCC’s TVStudy software or another program to calculate coverage.

However, a quick analysis based on an understanding of how height above average terrain, effective radiated power (ERP) and coverage are related can be useful before doing a complete coverage estimate. I’ve run some calculations for common tower heights and power levels and created tables that illustrate the trade-offs.

DISTANCE TO RADIO HORIZON
Increasing tower height can be expensive whether building a tower or leasing space. In most cases interim or auxiliary antennas will be mounted below the main antenna. One element to consider is the distance to the radio horizon from the antenna. The radio horizon is further than the true horizon due to refraction in the atmosphere. The distance to the radio horizon is also useful in calculating coverage from a site for two-way radios or even line of sight microwave, assuming there is sufficient power to overcome the path loss over the distance.

Table 1: Distance to radio horizon

Table 1 shows the distance to the radio horizon for heights above average terrain (HAAT) from 250 feet to 2,000 feet. I also show the distance as a percent of the distance for a common 1,000 foot tower. The formula for calculating distance to the radio horizon where HAAT is in feet is:

Distance (miles) to radio horizon =1.415*SQRT(HAAT)

For HAAT between 1,000 and 2,000 feet, a rough rule of thumb is a 5-mile increase in distance for each 250-foot elevation change (1 mile per 50 feet). Outside this range, the thumb fails. Looking at the formula and the table, you can see that as height increases, the incremental improvement in distance per unit of height decreases.

Table 2: Distance to noise limited contour at channel 25 (39.85 dBμV/m). Effective radiated

FCC UHF COVERAGE CHANGES WITH HEIGHT
Coverage is possible beyond the radio horizon, but without line of sight, more power is required and the amount of power varies with frequency band. I’ve shown how the distance to the radio horizon changes with HAAT, now let’s look at the impact on FCC coverage.

Table 2 shows coverage to the FCC service contour (39.85 dBμV/m) from a site with 300 kW ERP on channel 25. Notice that for the same height the FCC coverage goes substantially beyond the radio horizon distances in Table 1. The rule of thumb change for HAAT between 1,000 and 2,000 feet is a bit less, about 4 miles per 250 feet height change.

Table 3: ERP required to match coverage from 300 kW at 1000 feet above average terrain

CAN POWER OFFSET HEIGHT REDUCTION?
The final analysis looks at the change in ERP required to maintain FCC coverage at a fixed distance as height changes. Table 3 shows the results obtained with TVStudy’s “ptelev” utility for changes in height to a baseline facility with 300 kW ERP at an HAAT of 1,000 feet to maintain the FCC service area contour at 55.2 miles. To avoid extending the contour if the antenna is raised 250 feet, the ERP has to drop to 112.5 kW.

Why the big difference? Look at Table 1; this increase moves the radio horizon closer to the contour. At 1,500 feet the radio horizon almost matches the FCC contour distance at 1,000 feet and the required ERP drops to only 61.3 kW from 300 kW!

Broadcasters looking to move their replication antenna from a sidemount location to a topmount spot occupied by their old analog antenna have noticed a reduction in ERP. As these calculations are based on HAAT (height above average terrain), the difference would not have been nearly as great for stations on mountaintops as for “flatland” stations with tall towers.

What if the antenna has to go lower in height? Can a power increase offset the height reduction? Table 3 shows that for a reduction in HAAT from 1,000 feet to 750 feet, ERP has to be almost tripled to match the contour from the higher site. Going from 1,500 feet to 1,250 feet would require less than double the power. For a very tall tower, going from 2,000 feet to 1,750 feet requires a bit more than 50 percent power in the example we used.

Because of the impact of HAAT on the radio horizon, the required differences will change depending on the baseline ERP, HAAT and resulting coverage contour. I used the “ptelev” command line utility included with TVStudy to generate these tables. It can also calculate HAAT for non-flatland sites. A simpler method if TVStudy is not available, is the FCC Javascript application for calculating field strength at a given distance for a given HAAT and power (ERP) or distance to a given field strength for a given HAAT and power. It is available at https://www.fcc.gov/media/radio/fm-and-tv-propagation-curves.

REPACK REVIEW
Like many other broadcast engineers, I have been involved with the FCC 399 forms for reimbursement. Overall, I’ve been impressed with the job the reviewers are doing. For complicated questions, the review gets assigned to an experienced consulting engineer contracted by the FCC. They know how broadcasting works. While this helps them root out people asking for more than the FCC allows, I’ve also found they’ll remind broadcasters to doublecheck if they see they may have missed listing an item or cost that’s obviously needed. They are really interested in getting as accurate, complete, estimate of expenses as possible.

Broadcasters submitting forms and updates can help the reviewers. I’ve been told one of the most frustrating parts of the job is being presented with a Form 399 with loads of attachments with quotes and estimates and nothing tying the quotes and estimates back to the numbers in the Form 399. There may even be multiple quotes for the same thing, installation included in the transmitter quote and a separate quote for transmitter installation, for example.

To make things easier for the FCC, attach a spreadsheet that lists the item number in the Form 399, the file name of the quote the item is coming from, the line number or other description of where the item is in the quote, and the value in the quote to be used. This should match the Form 399 value; if not, include some explanation why—state sales tax could be one example. While we hope the review process will be complete by the time you read this, the 399’s will have to be updated as real quotes come in and final invoices are received.

If you wonder what other stations filed for in their Form 399, the forms are available in LMS. Use the Application Search atand enter the call letters of the station you are interested in. All applications will be listed, but the Form 399’s should be near the top. Click on the column heading on the page to sort results by that column.

Next month I’ll cover topics from the IEEE Broadcast Symposium taking place in Washington, D.C. this month. I welcome your comments and questions, email me atdlung@transmitter.com.

The FCC’s July 12 deadline for stations to file Schedule A, the engineering application for their post-repack facility, and Schedule 399, the request for reimbursement for that facility and other associated charges has passed. While I’m sure all of us breathed a sigh a relief when the last form was filed, there is a lot more work to do. Indeed, I suspect the rush to meet the deadline has produced applications for facilities that won’t, or can’t be built as filed and costs that are not fully documented. All this is going to have to be sorted out soon.

UPGRADES, HEADROOM AND MORE
In the case of the Schedule 399 filings, filers have already received an email notifying them they will have five business days after notification to correct any errors or provide any data missing on the form. Much of the confusion is likely to surround “upgrades,” replacing IOT (inductive output tube) transmitters with modern solid-state transmitters and the replacement transmitter power that will be allowed.

Some questions about how broadcasters with transmitters that are no longer supported by the manufacturer would be reimbursed for replacement transmitters—which the FCC stated would be considered an “upgrade”—remained unanswered until an FAQ was released less than two weeks before the deadline.

A key issue is whether stations that invested in larger transmitters, either for reliability or for future upgrades, will be reimbursed for replacement transmitters with similar headroom (extra power capability).

Many stations installed transmitters with two tubes, even if one could be pushed to meet their existing, licensed effective radiated power (ERP), because they didn’t want to be off the air if one tube failed.

Other stations installed larger transmitters to handle a future antenna design capable of elliptical or circular polarization. In a “like for like” replacement, broadcasters that made these decisions shouldn’t have to pay out of pocket for the extra headroom they had on their before-repack channel.

In other cases, the “like for like” replacement requirement, while certainly understandable and justified, can add complexity and extra work to repack. In some cases, rather than building an interim facility it may make sense to utilize the existing transmitter and antenna as the “interim” facility and build new for the new channel.

This sounds like the ideal solution for stations where a location for the new antenna is available—perhaps an old analog top-mount location or a spot opening up from a station that sold its spectrum and the existing transmitter either can’t be retuned or would be more expensive to retune than to replace.

While this wouldn’t be a “like for like” replacement, when considering the alternative, it has to be cheaper. A strict “like for like” would involve adding an additional antenna and line to the tower for interim operation on the existing channel so that the current antenna could be removed and the antenna for the new channel installed in its place.

If the tube transmitter was to be retuned or replaced with another tube transmitter, it is going to be very time-consuming since it would be a custom build and the station couldn’t be off the air for such a long period of time.

The only option, if an auxiliary transmitter was not available, would be to purchase or lease and install a new interim transmitter along with associated power and cooling gear.

Cost-wise, in either scenario a new transmitter is required, regardless of the antenna choice; but instead of one new antenna and transmission line in the “build new for new channel” case, two antennas will be needed and perhaps additional transmission line as well in a strict “like for like.”

The additional antenna means additional tower work. In many cases, the “build new for new channel” will be the cheaper, less risky approach, even if it involves an “upgrade” from a side-mount to a top-mount antenna.

A problem could arise if the antenna spot is higher on the tower than the existing antenna. The change in height above average terrain (HAAT) can be enough to modify the contour. Reducing ERP will bring the contour within the extension limits, but if the station has areas with dense population on the edge of its contour, it could reduce coverage by more than 5 percent of the population, causing the coverage check to fail. If a solution is found, it may not be the best one for real-world coverage.

Fortunately, from what I’ve seen in my work with the new channel assignments, there will be room to modify the patterns to something more useful, perhaps even restoring ERP to that authorized on a higher before-repack channel in the second priority filing window.

SCHEDULE A ENGINEERING COMPLICATIONS
I discovered another “gotcha” when working through facility designs for Schedule A designs that used mechanical beam tilt to shrink the contour off the back of a slot antenna to pull in the contour and protect other stations. The contours were incredibly hard to replicate with lower gain antennas. Maintaining the same antenna length requires lower elevation gain and a fatter elevation pattern.

Designs that meet the contour extension limits often result in less than optimum signal on the ground. Fortunately, as with the HAAT case above, there should be an opportunity to design and file for an antenna system that not only protects other stations but provides a good signal to the population when the 1 percent extension limit goes away in the second priority filing window.

These Schedule A engineering changes will likely result in some changes in the costs, which will have to be reflected in Schedule 399 updates as upgrades before reimbursement can be received for the “like-for-like” non-upgraded costs submitted on or before July 12.

The second priority window—in addition to allowing fixes to convoluted designs filed to comply with the FCC pattern replication rules—will allow stations to maximize and change transmitter locations. It is also the time to consider the role of single frequency networks in maximization plans.

Based on what I’ve seen studying the post-repack channel assignments, there will be many opportunities for stations to improve coverage and perhaps move transmitters from “suburban” locations into the market’s main antenna farm. Stations in a market may also want to swap channels to allow for an easier transition. In crowded regions like the northeast, a station may be able to increase power only if a station in an adjacent market increases power. All of this will have to be done in the second priority window before the freeze on coverage expansion is lifted for all TV broadcasters.

The July 12 deadline may have come and gone, but as you can see, many Schedule 399 and Schedule A forms are likely to require revisions before reimbursements start flowing and facility construction begins. Most of that work will have to be done within the next few months. No time to relax!

Doug Lung is vice president of Broadcast Technology, NBC/Telemundo stations. He welcomes your comments and questions. Email him atdlung@transmitter.com.

For more information on the repack, visit TV Technology's repack silo. 

On June 23, 2017, WNJU Telemundo 47 officially began broadcasting from One World Trade Center (1WTC) in New York, becoming the first station to return to this site since Sept. 11, 2001. Other New York City stations will be joining WNJU there soon—WCBS, WNBC, WPXN and WNET—sharing the UHF and VHF panel antennas mounted on the spire.

The UHF panel antennas, RFS models PEP40 and PEP96, contain two crossed dipoles (in an “X” configuration) with the +45-degree and –45-degree elements fed with two transmission lines. Transmitter power is split evenly between the +45 and –45-degree elements. The phase of the two feeds is varied to change the polarization from horizontal polarization only to full circular polarization. Transmitting only vertical polarization would be possible if the FCC allowed it. polarization from horizontal polarization only to full circular polarization. Transmitting only vertical polarization would be possible if the FCC allowed it.

John Gonzalez (L), WNJU director of technology and operations, and John Lyons, assistant vice president and director of broadcast communication of the Durst Organization, push the button to fire up the WTC1 broadcast antenna.

TESTING FIRST FULL-POWER SIGNALS
Prior to the official launch of WNJU’s signal from 1WTC we conducted test transmissions. In my RF Technology column “An Inexpensive Setup for Rapid DTV Field Measurements” (Jan. 11, 2015), I described the system used for testing coverage from test transmitters and antennas installed at 1WTC. These tests were done using circular polarization and showed the site was capable of penetrating the “midtown mountain” of high-rises to provide coverage on the north side of Manhattan.

When the WNJU transmitter installation at 1WTC was completed enough to allow overnight on-air testing at full power, we conducted measurements as close as possible to a circle with an 8-mile radius centered on 1WTC. Unlike the 2015 measurements, this time we used a WNJU ENG van with a 38-foot mast and two Blonder Tongue broadband log-periodic antennas mounted on top of the mast at the same height. One antenna was horizontally polarized and the other vertically polarized. Measurements were made using a Rohde and Schwarz ETL analyzer with drive test software and the same Hauppauge Aero-M tuners, LNA, splitter arrangement used for the 2015 measurements.

The WNJU 1WTC facility was transmitting 340 kW ERP, circularly polarized. In addition to a quick check on antenna performance, this gave me an excellent opportunity to see how vertical polarization performed in the field at outdoor antenna heights under various conditions. Where possible, measurements were made where we could see the 1WTC spire from the test site. In these locations, measured channel power was around –21 dBm on both antennas (vertical and horizontal polarization).

THE BENEFITS OF VERTICAL POLARIZATION
In some locations, particularly to the east in Brooklyn and Queens, it was difficult to find a site free of obstructions at the required angle and radius from 1WTC. I was surprised to see that in these locations—with clutter from surrounding high-rise apartment buildings—the horizontally polarized signal was down 5–6 dB from the unobstructed sites while the vertically polarized signal only lost 1 or 2 dB; this after peaking the antenna on the horizontally polarized signal.

This behavior was seen in multiple locations. At two sites in Staten Island on the same radial, we got strong, approximately equal signals on both polarities at a site by the water with a clear view of 1WTC. This site was too close to 1WTC, so we moved inland, but were only able to find a location partially obstructed by a building. As observed at the other sites, the vertical polarization had a 3–4 dB advantage over the horizontally polarized signal.

I haven’t had a chance to analyze all the data we collected, but the field observations indicate that in urban areas with clutter, the vertically polarized signal appeared to propagate much better than the horizontally polarized signal. It’s possible the receive antenna pattern had something to do with this, but as I noted, the received power was the same on both antennas when we had a clear, clutter-free, line-of-sight to 1WTC.

When repack work slows down, I’ll take a look at the echo plots from the ETL to how echoes (reflections) differed between the two polarities. Perhaps we should start looking for receive antennas that are circularly polarized or at least designed to be mounted for something other than horizontal polarization. Would a receive antenna tilted at 45 degrees work better than mounted for horizontal polarization?

HOW MUCH VERTICAL ERP IS ENOUGH?
One of the questions I heard frequently at the 2017 NAB Show and again at the ATSC Next-Gen TV conference in Washington, D.C., was, “How much of my power should I put in a vertically polarized signal?”

Many stations will have to change antennas, and often transmitters, as a result of the incentive auction. With at least part of the cost reimbursed by the government from auction proceeds, it may be worth spending some additional money to add or increase the amount of vertically polarized signal transmitted.

During the last round of maximization, I was able to increase vertically polarized ERP up to 50 percent of the horizontal ERP when using directional antennas at some stations with good results. With less directional antennas, getting sufficient transmitter power to transmit 1,000 kW horizontal and 500 kW vertical just wasn’t practical in 2009. Today it isn’t that difficult to achieve high power in a relatively small space.

The WNJU Rohde and Schwarz THU-9- EVO transmitter at WNJU is capable of producing up to 106 kW ATSC 1.0 power in six racks. Solid-state transmitters from Comark and GatesAir can now provide similar power density.

IMPLICATIONS FOR REPACK ANTENNA AND TRANMITTER DESIGN
Even though the benefits of additional vertically polarized ERP are clear, unless an antenna like the RFS PEP or Dielectric APT panel array is used the horizontal polarization (h-pol) gain and vertical polarization (v-pol) gain has to be set before the antenna is shipped. Adding v-pol ERP will require additional transmitter power to maintain the h-pol ERP, which is what determines the FCC contour.

Many stations had their ERP reduced as a result of being moved to lower channels in the FCC repack. See my column “Repack Complexities Abound” (February 2017), for a chart showing the amount of reduction for channel changes.

I expect many stations will be filing for power increases in the second priority filing window. If it isn’t possible to install enough transmitter now to make the maximized contour with the desired v-pol ERP, consider installing an antenna for the new channel with additional v-pol and hold off a bit on building the maximized construction permit until the transmitter can be upgraded.

With solid-state transmitters, this could be as simple as adding another rack of amplifiers and combiner, but it is important to let your transmitter vendor know your upgrade plans when making the initial purchase. Picking the right antenna and transmitter configuration now, even if it requires some short-term compromises, could pay off in the long run.

Doug Lung is vice president of Broadcast Technology, NBC/Telemundo stations. He welcomes your comments and questions. Email him atdlung@transmitter.com.

Broadcast TV antenna and transmitter manufacturers’ exhibits at the 2017 NAB Show were as packed as I’d seen since the DTV build-out a decade ago. One of the advantages of having these manufacturers in one place is that if one can’t deliver exactly what you are looking for, a short walk might reveal one that can. Here’s what I saw.

Broadcast engineers had a lot to look at and research. Most stations being moved to another channel as part of the FCC incentive auction repack will need a new antenna, a place to put it, and a new transmitter. Another antenna and transmitter may be needed to stay on the air while the main antenna is being replaced. Even stations that aren’t being repacked (including FM stations) may find they need an auxiliary antenna or site to stay on the air while work is being done on their primary site.

Although plans for a transition to ATSC 3.0 are still being formulated, smart engineers are making sure equipment they specify will work with ATSC 3.0.

Spinner AMS

ON THE SHOW FLOOR
Last year I described a product Spinner was showing that could detect arcs in antenna systems even when the arc occurred after multiple power dividers; but I was disappointed it wasn’t sized to work with the large line diameters used with high-power broadband antenna systems in the United States. Spinner recognized the demand and this year showed a version of its Antenna Monitoring System (AMS) that will work with line sizes up to 9 inches.

Spinner also had an item on display that they have been selling for many years, but which I hadn’t noticed. Their “Direct Access Unit” is a short piece of line permanently inserted in the transmission line at the top of the tower to allow an RF sweep of the line without the need to remove a section of line and install a test transition.

Considering the climbers, rigging and effort required to remove an elbow or section of large transmission line on the top of a tower, this device could pay for itself the first time a line has to be tested after the installation crew has left. The data sheet lists only 50 ohm units.

Fig. 1: The back of GatesAir Maxiva transmitter

GatesAir showed an updated version of its Maxiva solid-state transmitter that should make it easier to install and service. Fig. 1 shows the back of the transmitter.

Comark’s PARALLAX transmitter, which was still in prototype phase at last year’s NAB Show is now a finished product ready to ship. Both companies said they are offering low-VHF (Channels 2–6) versions of their transmitters for those stations that swapped out their high-VHF or UHF channels for low-VHF channels and cash.

Continental Electronics showed high-power UHF solid-state transmitter using Toshiba Gallium-Nitride power FETs in Doherty configuration. I’m not aware of other broadcast manufacturers using this device, at least in the United States, so it will be interesting to see how it performs.

The repack will be keeping antenna manufacturers busy for the next three years. While it’s likely most of the antennas will be similar to these they are replacing (probably a slot antenna), especially when directional patterns are required, I’ve seen more interest in broadband antennas capable of operating over several UHF channels.

Panel antennas, which I’ve covered before, are the most common broadband antenna, but broadband pylon designs, such as the cavity-backed slot, have been attracting attention due to lower windload and less complicated installation than panel antennas.

New this year was the Dielectric TFUGTH-BB pylon with a bandwidth of 60 MHz (10 channels). It is designed as a topmount antenna, compared with the full UHF band sidemount TFU-WB series introduced last year. Both antennas have sufficient input power handling to support multiple stations on one antenna.

Alive Telecom joined Dielectric and RFS to offer a cavity-backed slot antenna, the ATC-BCSE. While Dielectric and RFS have focused on making a standard antenna product that can be manufactured and ready for delivery on short notice, Alive offered a wider variety of pattern options and a nice, smooth elevation pattern. They had a model of the antenna on display at the NAB Show. When evaluating any of these broadband antennas with directional patterns, be sure to get a pattern for each of the channels on which they will be used. Patterns may vary from channel to channel!

ATSC 3.0
ATSC 3.0 is on the air now in Korea. Sinclair has an ATSC 3.0 experimental SFN operating in the D.C.-Baltimore area, and WRAL has an ATSC 3.0 experimental station on in Raleigh, N.C. Pete Socket, director of engineering and operations, described the construction of the station at WRAL in a presentation at ERI’s NAB Show breakfast.

While all the pieces of the ATSC 3.0 standard have not been finalized, a broadcaster could find all the components needed to put an ATSC 3.0 signal on the air from manufacturers at the NAB Show, as proved by the ATSC 3.0 broadcasts in Las Vegas.

Both the Comark and GatesAir transmitters include exciters with firmware, which can be switched to ATSC 3.0 with a license key. Rohde and Schwarz offered a software-defined modulator add-on to its current THU9 exciter that allows switching to ATSC 3.0. The Teamcast and Pro-Television exciters support ATSC 3.0 and can work with many new and existing transmitters. Enensys (which announced its acquisition of Teamcast at the show), Unisoft and Triveni showed packages broadcasters could assemble to begin broadcasting ATSC 3.0.

Receivers were harder to find this year. NAB showed the gateway it developed under its Pilot program. Avateq and Triveni joined forces to provide a device that provides full RF analysis of the ATSC 3.0 signal as well as analysis of ATSC 3.0 tables and data structure. DekTec’s DTA-2131 and Atsc3Xpert software-defined receiver was used in a number of the demos at the show. I heard comments about additional ATSC 3.0 test receivers becoming available, some based on a later version of the LG LGDT3307A demodulator chip LG showed last year, but no release dates or public announcements.

ATSC 3.0 offers capability far beyond that of ATSC 1.0 and it would be a shame to squander all the work that went into ATSC 3.0 by limiting it to replication of the same linear programmed, “single stick” ATSC 1.0-style broadcasts. Sinclair Broadcast Group has a plan for fully exploiting the capability of ATSC 3.0, which Louis Libin presented at show.

The plan builds on stations sharing spectrum and bandwidth and dynamically changing transmission characteristics as business demands—targeting different devices, users and services throughout the day and week. Universal coverage is assumed, which means multiple transmitters—an SFN—is required. Different spots can run on different transmitters in an SFN for targeted advertising. Broadcasters pool spectrum and data and are assigned broadcast “packets” to meet their needs. These “packets” could be on VHF or UHF or even split over multiple stations. “Packets” is in quotes because I’m not referring to IP packets alone, but the frequency and modulation over which these packets are carried. This is a different approach to broadcasting—a completely different universe. To better understand it, visit http://sbgi.net/one-media/ and start with the 2017 NAB Vision Paper available from that web page.

Next month I’ll consider repack antenna options—specifically the benefits of using elliptical or circular polarization. Recent tests with a full CP signal from the new antenna at One World Trade Center showed some interesting results.

If there are topics you would like me to cover or items I’ve missed, email me atdlung@transmitter.com.

To follow our online coverage, visit our repack silo, www.tvtechnology.com/repack.

WASHINGTON—The FCC has released the Auction Closing and Channel Reassignment Public Notice and files showing auction results, including stations that gave up their spectrum and those being repacked to another channel. These files show stations’ technical parameters and coverage on the new channels. Files also show the date they can start testing on the new channel provided testing can be coordinated with other stations impacted by the move. The “Linked Station Sets” are available on the same web page. The deadlines for completing the move to the new channels are also shown.

CHANNEL-CHANGE CONUNDRUM
Trip Ericson outlines a set of repacking reports and tools he’s assembled at his Rabbitears blog.

Engineers viewing the lists may be wondering why they have to change channels when their original channel is being assigned to another station in the same market. I think I’ve figured out why this is happening, at least at UHF.

As I described in my last column, the FCC uses dipole factor to determine a station’s protected contour and field strength. The result is stations on higher UHF channels require higher ERP than stations on lower UHF channels to provide the same coverage area. In a congested area, moving a UHF station to a lower channel will reduce its ERP and thus its field strength inside its contour. The lower ERP also means the station will cause less interference to other stations.

Consider this hypothetical case: station “A” on channel 20 and station “B” on channel 40, both with 1,000 kW ERP and non-directional antennas. The FCC moves station “A” to channel 21. Because it is already at 1,000 kW, its coverage and protection will shrink slightly as the required service threshold changes from 39.36 dBµV/m to 39.46 dBµV/m but it won’t cause more interference. Station “B” is now moved to channel 20, but instead of 1,000 kW it is assigned 655 kW ERP as the required field strength dropped from 41.2 dBµV/m to 39.36 dBµV/m. This lower field strength on channel 20 may now allow the FCC’s program to slip in another station on channel 19 or perhaps open channel 20 for use in another market.

Because interference is determined by the D/U (Desired/Undesired) ratio, stations that received lower ERP levels as a result of moving to a lower channel may be able to negotiate with stations on adjacent channels to regain lost power. If these stations also had ERP reductions, I’d hope they would cooperate and increase their power allowing all of them to regain their original signal strength. The antennas most viewers use at UHF have less gain at lower UHF channels, wiping out any dipole factor advantage.

In-market channel swaps may also have occurred as a result of different antenna patterns and different station locations. For stations on adjacent channels not at the same transmitter site, changing channels could reduce interference from one station and allow more interference from another, maintaining the FCC’s goal of minimizing coverage loss from repacking. In other cases the FCC’s software may have found putting stations moving to high-VHF from UHF on channels 8 to 12 and moving existing higher power maximized VHF stations to channels 7 and 13 where only one adjacent channel has to be protected allows tighter packing.

Some channel changes may have occurred to find room for stations in adjacent markets. A partial example of this is evident in the Rabbitears data for New York City and Hartford, Conn. WCBS is moving from channel 33 to channel 36, and WFSB is also moving from channel 33 to channel 36. Other stations in the northeast are also impacted.

Rabbitears now includes tools that can be used to figure out why these stations ended up on the channels they did. Start with the Repack Channel Assignments to find if a stations move is linked to other stations’ moves. The Linked Station Set number is in the “LSS” column. Click on it to see a list and map of all the stations in that set. The Rabbitears “Map for Repack Plan on Channel” is great way to see how channels are allocated in a given area. Enter a channel and the map will display all stations on that channel and adjacent channels. The “Map for Repack Plan on Channel 36” shows how tightly packed the channels are in the northeast. Click on the flag at each stations site to see a link to the “Repack Checker”, which will show what channel that station can use and the impact of the selected station on other channels.

Channel 36 is in a “sweet spot” because only one adjacent channel has to be protected. Channel 14 also has only one adjacent channel to consider, but comes with a major disadvantage.

As UHF stations are squeezed into channels below 37, it isn’t surprising some stations will end up on channel 14. The 450-470 MHz land-mobile band is assigned nationwide so unless the channel 14 stations’ transmitter sites are in remote areas, far away from two-way radio repeaters, there are likely to be problems. A total of 33 stations will have to move to channel 14 and some of these are in major markets where there is a lot of activity in the 450-470 MHz band. Full-power stations will be moving to channel 14 in San Jose Calif, Denver, Washington, D.C., Phoenix, and San Antonio unless they can find an alternative channel. In markets where channel 14 and 15 are both assigned, passive intermodulation may create interference in the land-mobile band that can’t be fixed by filtering.

Interference could delay the repack in markets where these channels are used. The FCC recognizes the issues and costs with channel 14 – there is a check box on the reimbursement Form 399 if the station is assigned channel 14, but I’m not sure the intermodulation issues (which Charles Rhodes has expertly described in this magazine multiple times) between channel 14 and 15 and other users in the 450-470 MHz band have been recognized. 

ZOMBIE OR ‘LOWFER’—WHICH IS WORSE?
The FCC allowed station owners to sell their spectrum in the auction but keep the license for a future channel-sharing agreement. These stations, having a license but no spectrum or sharing partner, have been termed “zombie stations.” The zombies are on the move, searching for stations they can share channels with or, if the FCC allows, an opportunity to sell their license to someone who has spectrum. The zombies will soon be joined by LPTV and translator stations, which the FCC recently allowed to enter into spectrum sharing agreements with full power and Class A stations, as well as other LPTV and translator stations.

The good news for the zombies (and displaced LPTVs) is that if they find a host (sharer) they may be able to maintain good or improved over-the-air coverage on a UHF or high-VHF channel. The 17 “lowfers,” those stations that gave up their UHF or high-VHF station to move to low-VHF, are likely to lose most of their over-the-air coverage. They can multicast their programming on another station, but not channel share.

I wrote several articles about the problems with low-VHF during the DTV transition. Googling will bring up some of them, as well as stories about WBBM’s problems with channel 3 in Chicago. Briefly, the problem is that to be efficient, antennas need to be huge (a half wavelength at channel 2 is almost 9 feet!). Indoor antennas are useless because noise from household appliances with motors, switching power supplies, and other devices will wipe out the DTV signal. Ignition noise from passing cars or trucks and lightning storms anywhere in the vicinity will interrupt reception even with a good outdoor antenna.

Please let me know if you have repack or other items you’d like me to cover! Email me at dlung@transmitter.com.

See also:

New Low-VHF DTV Stations Causing PSIP Problems (June 2014)

Solving VHF DTV Reception Problems (April 2009)

Low-Band VHF DTV Revisited (May 2004)

This story has been updated from its previous version. The paragraph starting with "Rabbitears now includes" has been added. 

This month I’m continuing my coverage of the 2016 IEEE Broadcast Symposium, with a focus on presentations about ATSC 3.0 and the transition from ATSC 1.0 to ATSC 3.0. As expected, ATSC 3.0 received much attention during the conference, both in the presentations and in discussions between the sessions.

In the tutorial session “The Practical Side of ATSC 3.0,” Mark Earnshaw, senior engineer at Coherent Logix, presented an excellent overview of the ATSC 3.0 Physical Layer. Earnshaw knows the ATSC 3.0 system inside and out, and I strongly encourage readers to take advantage of any opportunity they might have to catch one of his presentations. It would provide an excellent basis for a webinar or, more likely, series of webinars. The presentation is in the IEEE Broadcast Symposium Proceedings.

‘WHY ATSC 3.0?’

If you’re not yet convinced there is a need for ATSC 3.0, the presentation “Why ATSC 3.0?” by Dave Siegler, vice president of technical operations at Cox Media Group, provided some arguments for making the transition. He outlined what focus group studies show consumers want, but today’s TV can’t deliver: better pictures, better sound quality with more tracks and customization, targeted advertisements, enhanced emergency alerts, and coverage on mobile devices.

Siegler also pointed to business trends, including cord-cutting/cord-shaving, an increase in over-the-air viewing and increased usage of over-the-top services. He showed how, with ATSC 3.0, broadcasters can meet consumer wants and take advantage of the business trends. Why ATSC 3.0? “Opportunity!”

While I don’t focus on content creation in this column, I know many readers are involved with it. Skip Pizzi and others at NAB are leaders in the effort to define the framework required for delivery of ATSC 3.0 content over IP and to enable new features such as localized insertion of ads, hybrid broadcast/internet services, interactivity and more. If you haven’t been following the development of ATSC 3.0 upstream of the transmitter, try to secure a copy of Pizzi’s presentation “Content Creation for ATSC 3.0” from IEEE BTS or NAB.

Rich Chernock, CTO at Triveni Digital and chair of ATSC Technology Group 3, presented an update on the ATSC 3.0 status, noting some products should be available in 2017 with a commercial launch in 2018–2020.

Chernock cautioned that to get around the “chicken and egg” scenario—no consumer devices because no content being broadcast; no content being broadcast because of no consumer devices—broadcasters should start putting ATSC 3.0 on the air.

Many of the emails I receive about ATSC 3.0 from viewers and broadcasters express concern over loss of ATSC 1.0 service. In the petition for rulemaking to allow broadcast of ATSC 3.0, the proponents (broadcasters, CTA, NAB) committed to keeping stations available in ATSC 1.0 format during the transition. Without new spectrum, this will require channel-sharing for both ATSC 1.0 and ATSC 3.0 content.

OPTIMIZING ATSC 1.0

Several presentations in Friday afternoon’s “Next Gen TV” session examined the practical side of the transition to ATSC 3.0. I found the presentation “Optimisation of ATSC 1.0, an essential tool for the ATSC Transition” by Guy Bouchard, CBC senior manager for new broadcast technologies, particularly interesting. It covered a topic that will not only be essential for a successful ATSC 3.0 transition, but any station sharing an ATSC 1.0 channel.

Engineers who have had to add more channels to their 19.392 Mbps ATSC 1.0 stream have probably employed many of the techniques Bouchard described, including use of statistical multiplexing, minimizing overhead and PSIP and potentially reducing resolution. Bouchard explained the tradeoffs between these techniques, the impact on TV receivers and some suggestions for optimizing ATSC 1.0 bandwidth.

Statistical multiplexing (“stat-mux”) can cause problems for some receivers. Bouchard said some legacy TV sets that worked well with video streams with a minimum of 5 Mbps, an average rate of 7 Mbps, and a maximum rate of 9 Mbps showed glitches when the excursion was higher. Recent sets had no issue with these streams. Obviously, using such a low excursion in a statmux pool leaves little room for adding additional streams.

Reducing the null packet reserve is an important part of optimization. It requires making sure encoders don’t occasionally output higher bit rates than they should. This is primarily a problem with older encoders. After all optimizations and testing on multiple receivers, Bouchard was able to reduce null packet allocation from 0.5 Mbps to 0.1 Mbps.

This matches my experience. I’ve found 125 kbps (+/–25 kbps) of null packets works fine with encoders made in the last three years, good PSIP rate control and statistical multiplexing.

Stations’ TSIDs could cause channel-sharing problems. Each station has a unique TSID (Transport Stream Identifier) assigned by the FCC.

Bouchard found some TV sets allow multiple occurrences of the same TSID, while others dis-allow a second occurrence of a unique TSID. With several stations on the same transport stream, there will be a unique TSID in PAT, but several TSIDs in VCT. Bouchard said most receivers took the change well, but some were confused and some even had to be reset to factory settings.

Bouchard’s presentation contained useful tips and techniques for any stations considering channel-sharing as part of the ATSC 1.0 to ATSC 3.0 transition or as a result of the spectrum auction.

COVERAGE AREA

Channel-sharing on ATSC 3.0 involves more than dividing up bits, as the number of bits will impact coverage. The presentation “Coverage of Various ATSC 3.0 Transmission Modes” by Bill Meintel and Dennis Wallace at Meintel, Sgrignoli and Wallace described the many options and range of performance available for ATSC 3.0 transmission. They also provided practical examples showing population coverage with different service combinations compared with ATSC 1.0.

Most ATSC 1.0 coverage studies use the FCC outdoor planning factors based on a directional outdoor antenna mounted 30 feet above ground. Determining service within the coverage area is more difficult, moreso when the different thresholds for different ATSC 3.0 modes are considered. In these situations, a field strength plot isn’t particularly useful. I like the paper’s approach—show coverage-based difference between the field strength and the threshold for reception. The paper used three levels: 20 dB or more above threshold, 10–20 dB above threshold and 0–10 dB above threshold.

Fig. 1: PLP1 16.5 dB SNR 14.92 MBps enhancement layer LDM

Fig. 2: PLP2 0.53 dB SNR 3.1 MBps core layer LDM

I’ll describe one of the scenarios using Layered Division Multiplexing (LDM), presented showing a likely early ATSC 3.0 transition scenario. The enhancement layer had one PLP providing ~14.9 Mbps of capacity and an AWGN threshold of 16.5 dB. With HEVC, it should be capable of carrying three or four HD+ services. Coverage is mapped in Fig. 1. The robust core layer had one PLP providing ~3.1 Mbps at an AWGN threshold of 0.5 dB, enough for two to four robust/mobile SD services plus audio. Robust core coverage is shown on the map in Fig. 2.

Table 1 shows the predicted service comparison for this configuration. Note that compared to ATSC 1.0, although the loss is small, not all the population predicted to receive ATSC 1.0 service will be able receive ATSC 3.0 HD+ service. However, a significantly larger population will get the robust SD and audio ATSC 3.0 service than the ATSC 1.0 service. Thanks to Bill Meintel and Meintel, Sgrignoli and Wallace for letting me use their slides.

Table 1: Predicted service comparison fixed and mobile LDM scenario

If you are interested in copies of the presentations, contact the authors or IEEE Broadcast Technology Society (http://bts.ieee.org/about-bts/contact-bts.html) to check on availability. If not a member of IEEE BTS, consider joining!

I welcome your comments and questions. Email me atdlung@transmitter.com.

I first attended the IEEE Broadcast Symposium 20 years ago when it was held at the Hotel Washington and it remains the “must attend” event of the fall conference schedule. This year’s symposium in Hartford, Conn., was well attended, with many local broadcast engineers and engineering students attending the sessions; the papers were interesting and relevant; and the food, hospitality and conversations at lunches and receptions were excellent.

PRE-SYMPOSIUM TOURS

The day before the symposium, attendees had an opportunity to tour the RFS facility in Meriden, Conn. and Hitachi-Comark, in Southwick, Mass. The RFS tour gave attendees a chance to see what RFS was doing to prepare for the repack. The group saw the space RFS had reserved for building antennas for the repack (Fig. 1) and also heard about its software and technology for optimizing slot antenna patterns.

RFS room for repack antennas

At the Hitachi-Comark plant, the company had a fully loaded PARALLAX solid-state UHF TV transmitter putting 27.5 kW into a dummy load (Fig. 2). The group was able to see the transmitter’s performance on an ETL analyzer. We also had a chance to see how the transmitter was assembled. The modular design makes it easy to build transmitters for different power levels and should allow Comark to ramp up production as needed to meet demands for transmitters as part of the repack.

REPACK PRESENTATIONS

The papers covered a wide range of topics of interest to broadcast engineers, with several focusing on new technology and technical regulatory issues like the upcoming repack of TV channels. I’ll cover repack issues this month and in future columns, I’ll discuss presentations that describe application of new technologies for the repack and the transition to ATSC 3.0.

Even though two stages of the FCC’s incentive auction had been completed before the symposium ended, many questions remained about what broadcasters would have to do to move to their new channels when the auction ended and how they would be reimbursed.

Joe Davis, president and founder of Chesapeake RF Consultants LLC, presented a “TV Repack Update—Wait, and Hurry Up!” The FCC has provided a beta test of the Schedule 399, Form 2100 online for reimbursement of eligible expenses and Davis outlined the items in Schedule 399, noting that the FCC wants to see a description of the station’s plan for changing channels. If facilities are shared (tower, antenna, site), the commission wants to see the other stations sharing the site to make sure the sum of the reimbursements for the shared items doesn’t exceed 100 percent of what’s allowed. He said the FCC will be updating the reimbursement cost soon. [As of this writing, the beta test of Schedule 399 has ended, but new costs have not been released.]

Davis summarized the various filing windows opening after release of the channel assignment Public Notice. I’ve covered the filing windows in a previous column, but to summarize, they include a window ending three months after the Public Notice is released for filing construction permits for the FCC assigned facilities; a priority station filing window after that for modified facilities for stations with excessive loss of population or for stations that received a waiver of the original CP deadline; and a non-priority station window where stations can request expanded facilities and alternate channels. Digital LPTV and translator stations on the air when the Public Notice is released will have a window to file for a displacement channel and, finally, full-power stations that are not repacked will see the freeze on contour extension and channel substitution lifted.

Full power PARALLAX operating at Comark

Davis said expansion and channel change proposals will be viewed unfavorably if they impact the repack. He noted that the FCC’s phased approach seems to be in conflict with the goal of clearing wireless spectrum first—under the plan, high-channel number stations will be last in the daisy chain.

After describing how the FCC staged the transition modeling based on the time it takes to receive permit approvals, install antennas, etc., he noted, ironically, the FCC didn’t see availability of RF consultants and structural engineers as an issue. Why? Because the FCC requires them to finish in three months! Download Davis’ presentation at www.rf-consultants.com/ieee.

IMPACT OF REPACK ON FM STATIONS

FM stations have been ignored in the FCC’s repack planning, and Jim Stenberg, principle engineer, broadcast RF for American Tower Corp., sees that causing problems for TV and radio broadcasters alike. In his presentation, “TV Repack Implications for FM Station Operations,” Stenberg estimated 1,153 towers in the United States have co-located FM and TV and 2,368 FM radio stations and translators could be impacted by the repack, based on FCC and ASRN data. Very few of these have auxiliary transmitters on different towers.

Obviously, extensive tower work related to the repack will impact FM stations. Tower lease agreements with limited windows for FM power reductions or shutdowns could significantly delay repack tower. The obvious solution, Stenberg noted, is for FM stations to have an off-site auxiliary facility. He said most master FM systems can handle one or more aux stations, depending on physical space and power handling capability.

There is a problem though. Who pays for it? The incentive auction Report and Order states, “For example, where multiple stations share a tower, a reassigned station that makes changes may be required to cover certain expenses incurred by other tower occupants. In such circumstances, the Commission will consider a claim from the reassigned station for reimbursement of such costs, so long as the reassigned broadcaster has a contractual obligation to pay these expenses through a contract entered into on or before [June 2, 2014].”

Stenberg noted that most stations’ lease agreements do not have such a contractual obligation. He said ATC has asked for clarity on how this will affect FM stations on TV towers, but as of his presentation, FM stations were not directly able to submit (or have the TV station submit) expense reimbursement for temporary auxiliary facilities in most cases.

If you are interested in copies of the presentations, contact the authors or IEEE Broadcast Technology Society (BTS) to check on availability. If you are not a member of IEEE BTS, consider joining!

Doug Lung is vice president of Broadcast Technology, NBC/Telemundo stations.He welcomes your comments and questions. Email him at dlung@transmitter.com.

Many stations will replace transmitters, RF systems, line and antennas as part of the channel repack after the incentive auction and it makes sense to select gear that will work for ATSC 3.0. A move to ATSC 3.0 could be as simple as replacing the transmitter’s exciter and providing an IP link from the studio, but a system designed for ATSC 1.0 alone may not support single frequency network operation, the full ATSC 3.0 channel bandwidth or the same power level as ATSC 1.0. This month I’ll cover some of the things to consider when making changes at the transmitter site.

ATSC 1.0 provides support SFNs (also called distributed transmission systems) but they haven’t been widely used in the United States, likely because it is difficult to avoid interference between the transmitters unless they are isolated by terrain. To make matters worse, different ATSC 1.0 receivers will handle the interference differently.

With ATSC 3.0, as I’ve pointed out in earlier columns, most of those problems go away with proper selection of the OFDM guard interval. However, as with ATSC 1.0, all of the ATSC 3.0 transmitters on a channel in a SFN have to transmit exactly the same signal. Optimization of the SFN requires the ATSC 3.0 signals be emitted from each transmitter at different but precise times.

This means the signal from the studio sent to the transmitters either has to contain all the data, exactly as it is to be transmitted, or that the signal from the studio has to include enough metadata to allow each of the transmitters in the SFN to create and emit exactly the same signal.

TWO APPROACHES
The first approach essentially splits the exciter between the transmitter and the studio. This requires extra bandwidth, as all of the overhead needed to create the constellation has to be added at the studio. At the NAB Show, studio transmitter link (STL) bandwidths of up to 250 Mbps were suggested for this approach.

The second approach, currently being finalized in ATSC S32, allows sending the different program and data streams, signaling information and timing information to the transmitter in a way that the exciter at the transmitter can take all these streams, add the appropriate error correction to them, create the constellation waveform and emit a signal at the correct time that matches all the other transmitters in the SFN. This standardized approach should allow an SFN using exciters from different manufacturers.

The good news is that any microwave or fiber link that supports IP transmission should work for ATSC 3.0, but the data rate required by the first approach might be for many existing microwave STL links. The ATSC 3.0 SFN standard will help solve that problem. Either approach will require additional hardware at the studio and the transmitter site.

The good news is companies are aware of this—we saw an STL using the first approach working at the NAB Show and companies are planning support for the more efficient ATSC 3.0 SFN/STL technology.

Any transmitter that can handle ATSC 1.0 should be able to transmit ATSC 3.0 with a change of exciter. It may not, however, be able to match the output power of ATSC 1.0. The reason is that ATSC 1.0, a single carrier system, has a lower peak-to-average power ratio (PAPR) than ATSC 3.0, a multicarrier OFDM system.

A simple way to check this is to look at the specifications for the transmitter. Most transmitters sold today are offered for both ATSC (8-VSB) and DVB (COFDM) use, but the power levels are not always the same.

Comark specifies the same power levels for both modulations for its PARALLAX transmitter, as does Rohde & Schwarz for its current THU9 transmitter. However, the new Doherty amplifiers R&S showed at the NAB Show have a higher power rating for ATSC, as do GatesAir’s Maxiva “PowerSmart” transmitters. Check the datasheets for specifics and keep this in mind when specifying a replacement transmitter’s output power.

The ATSC 3.0 standard includes tools for reducing PAPR, including tone-reservation, but they can have an impact on available data bandwidth. Annex M of the ATSC Proposed Standard A/322—Physical Layer Protocol describes a peak-to-average power reduction algorithm for tone reservation and a possible one for the active constellation extension (ACE) method. Find the latest version at www.atsc.org.

IMPACT ON COMPONENTS
ATSC 3.0’s higher PAPR will also have an impact on the components at the output of the transmitter. Even if the average power is unchanged, the higher peak power will result in higher RF voltages, potentially leading to arcs and burn-out in RF system components like filters, transmission line and antennas.

Derek Small, senior engineer with Dielectric, outlined the power handing capability of different filter designs under ATSC 1.0 and ATSC 3.0 in his NAB Show presentation, “Efficient UHF Tunable Waveguide TE10 Mode Filter.” Broadcasters want tunable filters to allow them to change channels without replacing their RF system. Most tunable filters use tunable coaxial/transitional mode cavities. They are compact compared to waveguide designs, but have greater loss.

Fig. 1: A slide from Small’s NAB Show presentation on Dielectric’s tunable waveguide filter that has lower loss than the tunable coaxial/transitional mode cavity filters and greater power handling capability. The significant probe penetration in these filters leads to higher electric field densities, making them more susceptible to breakdown with ATSC 3.0’s higher PAPR and potentially reducing the maximum power they can handle compared to ATSC 1.0.

Small and Dielectric developed a tunable waveguide filter (Fig. 1) that has lower loss than the tunable coaxial/transitional mode cavity filters and significantly greater power handling capability (Fig. 2). Henry Fries, vice president of operations with Comark, told me that the company plans to use these filters with its new Parallax transmitter.

The ATSC 3.0 COFDM signal can occupy up to 5.83 MHz of a 6 MHz channel, more than the 5.38 MHz occupied bandwidth of an ATSC 1.0 signal. Current plans for ATSC 3.0 in the United States do not change the emission mask or out-of-channel emission limits—ATSC 3.0 broadcasters will have to comply with the existing emission mask.

One way to accomplish this is to reduce the number of carriers transmitted, reducing the occupied bandwidth to 5.51 MHz. See Table 7.1 of ATSC A/322 for details. Another option is to use a more complex filter.

The same breakdown voltage concerns Small mentioned in his presentation should apply to tuners in transmission lines and parts of antennas with high electric field density. Myat has created a document that contains, among many other things, tables and formulas for calculating the average power and peak power handling capability of transmission lines. Download the PDF from www.myat.com/images/stories/pdfs/Engine.pdf. The “Peak Power Rating and Production Test Voltages” table from the document shows the peak power limit for different sized line. Note that these values are for 1:1 VSWR and do not include modulation. Peak and average power ratings will be reduced for realworld conditions!

Broadcasters looking to reach indoor antennas and portable devices will be adding elliptical polarization, increasing the amount of power in filters, transmission lines and antennas. Making sure these components can handle higher peak powers with ATSC 3.0 will help avoid costly burnouts.

The transmitter site changes required for ATSC 3.0 are small compared with those required at the studio and in viewers’ homes. With a bit of planning when changing channels for the repack or upgrading facilities, the change at the transmitter site could be as simple as loading new firmware into the exciter!

Doug Lung is vice president of Broadcast Technology, NBC/Telemundo stations. He welcomes your comments and questions. Email him atdlung@transmitter.com.

WASHINGTON—A successful plug-fest in Baltimore, an impressive display of ATSC 3.0 technology at the NAB Show in Las Vegas, an FCC Public Notice requesting comment on a widely supported request to allow broadcasters’ use of ATSC 3.0, and a packed 2016 ATSC Broadcast Television Conference-“Countdown to Launch” in Washington, D.C. in May indicates ATSC 3.0 may soon be coming to a TV or tablet near you!

TEST TRANSMISSIONS
ATSC 3.0 test transmissions are on the air now from Sinclair’s experimental single frequency network (SFN) on Channel 43 in Baltimore and Washington, D.C. Over-the-air ATSC 3.0 was on display at the NAB Show from two different transmitters, and multiple tests, including VHF over-the-air testing, have been conducted in Cleveland.

Manufacturers I talked to at the ATSC conference told me they are getting requests from several broadcasters for equipment for ATSC 3.0 tests, indicating we may see more ATSC 3.0 experimental test stations on the air later this year.

ATSC 3.0 transmissions, of course, aren’t of much use unless there are receivers. One of the most significant ATSC 3.0 products I saw at the NAB Show was a chip a third of the size of a postage stamp—more about that later.

I remember sitting in sessions at the NAB convention and at the IEEE broadcast symposium two decades ago trying to figure out how PAT, PMT, PIDs, ETT, EIT, STT, VCT, etc., all fit together to create an ATSC DTV stream. How was I going to get this to the transmitter? Skeptics said “Table 3,” showing 18 different display formats for video, was overly complicated, but at least there was only one transmission format—8VSB at 19.39 Mbps. Now, in 2016, we’re looking at a standard that offers an almost endless number of options for data rate and robustness and multiple ways to package and deliver content (or data) to viewers (or devices). It is complicated, but sessions at the NAB Broadcast Engineering Conference and a full-day tutorial before the ATSC Broadcast Television Conference helped prepare attendees for the new standard.

Perhaps the best way to learn is to put hardware together and see what works and what doesn’t.

Plug-fests are important because they give manufacturers a way to see if their understanding of the ATSC 3.0 specifications are correct and whether a signal generated on manufacturers’ equipment can be received on other manufacturers’ equipment. The purpose of the testing is not to rate performance, but to see if there are parts of the specifications that need to be clarified or corrected and make sure manufacturers agree on how specific elements are generated and decoded. During the plug-fest manufacturers can update their code and retest as time allows. Reports of plug-fest results, even inside ATSC, do not identify manufacturers by name.

A unique feature of the Baltimore plug-fest was that participants had an over-the-air signal from Sinclair’s experimental station they could use to check their receivers. One of the many elements checked in the Baltimore plug-fest was the ability to generate and decode layered division multiplexing (LDM) signals, an important feature in ATSC 3.0 that I described last year in RF Technology “LDM-Stacking Signals for Improved Performance.”

Fig. 1: Zenith Electronics, LG Electronics, Harmonic, Triveni, GatesAir, Dolby and Digital Alert Systems had a rack of equipment generating an ATSC 3.0 signal that included prerecorded and live content as well as AWARN emergency alerts

So far, the plug-fests have focused on the physical layer. Expect to see additional plug-fests where upper layer compatibility is checked.

It was encouraging to see that even with the standard still under construction many companies were able put together demonstrations of ATSC 3.0 at the NAB Show. One example of cooperation between companies was evident at the entrance to the ATSC 3.0 Broadcast Pavilion at the back of South Hall Upper. Zenith Electronics, LG Electronics, Harmonic, Triveni, GatesAir, Dolby and Digital Alert Systems had a rack of equipment (Fig. 1) generating an ATSC 3.0 signal that included prerecorded and live content as well as AWARN emergency alerts. The signal was sent to Black Mountain where it was transmitted over the air on Channel 18. For details on the gear, see Triveni Digital's press release. Sinclair provided an over-the-air ATSC 3.0 signal from a test transmitter on Channel 45 at Black Mountain.

ATSC 3.0’s use of Internet Protocol requires a different architecture than ATSC 1.0. Programs can be encoded and simply sent as transport stream over IP; encoded with an ISO BMFF encoder streamed using MPEG Multimedia Transport (MMT) or encoded using Dash and streamed using Real Time Object Delivery over Unidirectional Transport (ROUTE). The different program elements, as well as signaling, are sent to an ATSC Scheduler that determines the appropriate place and time in the transmitted signal (physical layer) for each element. Finally, the signal is sent to the STL and on to the modulator, transmitter and antenna.

Enensys had a demonstration set up in the lobby at the ATSC Broadcast Television Conference showing a complete ATSC 3.0 signal path from encoder to modulator with HEVC encoders, a ROUTE server, their ATSCheduler, IP Guard error correction and a modulator. Enensys plans to implement the STL/SFN interface being developed in the ATSC TG3-S32 small group.

Enensys also handed out a large poster showing details of the ATSC 3.0 architecture. I found it a big help in understanding how all the pieces of ATSC 3.0 work together. Download it here.

WHAT ABOUT RECEIVING?
Transmitting ATSC 3.0 is fine, but how do you receive it? I was happy to see Avateq showing a monitoring receiver for ATSC 3.0 that not only displayed the RF signal characteristics and performance, but allowed decoding the tables transmitted in the bootstrap signal and preamble. For now, this is the only piece of equipment I’m aware of that can do a full analysis of an ATSC 3.0 signal starting with the RF waveform.

Fig. 2: The ATSC 3.0 receiver chip used in the over-the-air gateway LG Electronics was showing in the ATSC Consumer Experience at the NAB Show.

About that chip I mentioned earlier... The ATSC 3.0 receiver chip used in the over-the-air gateway LG Electronics was showing in the ATSC Consumer Experience (Fig. 2). If you are familiar with LG’s ATSC receiver chips, all (as far as I know) of LG’s ATSC/QAM receiver chips are in the LGDT-330X family. Until recently, the LGDT-3306A was the latest member of the family and included ATSC 1 and QAM demodulators.

The LGDT-3307A chip, shown at the NAB Show, includes ATSC 1, ATSC 3.0, QAM demodulators. The model number implies the LGDT-3306A was the last LG ATSC demodulator without ATSC 3.0 capability. Neil Smith, one of Zenith Electronic’s lead R&D engineers on the chip, was clearly proud of the company’s accomplishment. He hopes to see the LGDT-3307 in a wide range of devices, including USB tuners.

Having an ATSC 3.0 receiver in silicon is a major milestone. One of the DVB-T2 pioneers told me it took a year after the DVBT2 standard was finalized until silicon was available for it, but with ATSC 3.0, silicon was available even before the standard was finalized.

Fig. 3: At the NAB Show, Airwavz.TV demonstrated the “Quarterback,” an Android smartphone case that includes a battery, ATSC receiver and a unique fold-out antenna.

I noticed Bonnie Beeman of Airwavz. TV in the ATSC 3.0 Consumer Experience walking around with a smartphone that was receiving TV (Fig. 3). The Android smartphone’s case (called the “Quarterback”) included a battery, an ATSC receiver, and a unique fold out antenna on the back of the case. Unfortunately, it was receiving an ATSC 1 signal from KBLR, not one of the ATSC 3.0 transmissions. Seattle-based Airwavz. TV wants to create an ATSC 3.0 version and Beeman explained that it would be a valuable way to deliver information in emergencies, when cell sites are often jammed or fail. The ATSC 3.0 robust bootstrap has two bits for emergency alerting that can be used to wake up cell phones or TVs when new or updated emergency information is available.

The pace of activity in the first five months of 2016 is an indication ATSC 3.0 is off to a good start. It isn’t too soon to start thinking about what changes might be needed at the transmitter site for ATSC 3.0. More on that next month.

Doug Lung is vice president of Broadcast Technology, NBC/Telemundo stations. He welcomes your comments and questions. Email him at dlung@transmitter.com.

HAWAII—The looming repack and stations' aging transmitter plants had broadcast engineers taking a fresh look at transmitters and other RF gear at NAB 2016. Fortunately, they had a lot to see!

TRANSMITTERS

Comark was back in the Central Hall location it shared with Thales in the early days of ATSC 1. I remember Comark displaying UHF IOT transmitter cabinets there. This year, Hitachi-Comark's new solid-state Doherty transmitter, which is capable of generating the same power as one of those turn-of-the-century tube monsters, was easy to miss in its prime spot in the Hitachi exhibit as it occupied only one 30-inch cabinet. A 100 kW transmitter would take only four racks!

The Hitachi-Comark PARALLAX uses the latest NXP/Ampleon transistors in a Doherty configuration. Comark claims efficiency around 45 percent across UHF channels 14–36. The amplifier can be configured to operate on higher channels for export or for those unlucky stations ending up in the wireless band. The bandwidth choice is a good compromise between making the amplifier completely broadband and maximizing efficiency. The amplifiers are water-cooled, with the coolant isolated from the aluminum heat sinks so that standard copper plumbing can be used without worrying about copper ions degrading the aluminum.

Photo 1: Inside the Hitachi-Comark PARALLAX

One nice feature of the transmitter is that the amplifier combining system is flexible enough to allow adding amplifiers if additional power is needed in the future. While the combiners would have to be changed, it looks like it could be done if the plumbing and wiring was in place. You can see the combiners in view of the rear of the transmitter in Photo 1. The amplifiers are powered by the same air-cooled, high-efficiency plug in GE power supplies that GatesAir selected for its solid state transmitters.

The PARALLAX shown included EXACT exciters designed by TeamCast exciters that are ATSC 3.0 ready. Jack McAnulty told me that Comark plans to have a complete transmitter up and running at the factory in October so that attendees of the IEEE Broadcast Technology Symposium in Hartford, Conn. can visit the factory and see for themselves how the transmitter performs.

Comark's new transmitter will be competing against established high-power solid-state transmitters from GatesAir and Rohde & Schwarz. Both companies were showing their transmitters at NAB and describing their ATSC 3.0 capability while touting recent sales and installations.

Rohde & Schwarz has upgraded the amplifiers in its THU9 series transmitters. While equipped with the same NXP/Ampleon transistors as the older amplifiers, Rohde & Schwarz has improved the design of the amplifier and cooling to allow the amplifiers to be used at higher ATSC (single carrier) power. A six-rack THU9 transmitter can now provide up to 108 kW ATSC power (pre-filter).

GatesAir introduced two higher power air-cooled transmitters—the UAXT-12 (10.8 kW) and UAXT-16 (14.4 kW). If sufficient air is available, these transmitters will greatly simplify installation by not requiring plumbing to outdoor heat exchangers. Combining one of these transmitters with a tunable mask filter could make for a very flexible and almost “plug and play” transmitter installation.

FILTERS & RF COMPONENTS

All TV transmitters require “mask” filters that are tuned to the channel being transmitted and reduce emissions outside the channel to FCC limits. Much of the interest in antennas and RF filters is driven by the repack, but smart buyers will be also be making sure the filters will work after they switch to ATSC 3.0. ATSC 3.0's OFDM modulation can occupy more of the channel and has a higher peak-to-average power.

For the repack, stations may decide to install an “interim” transmitter on their existing channel to use while the main transmitter (and antenna) is being switched to the new channel. In such cases, having a tunable mask filter will allow the interim transmitter to be used as a backup on the new channel after the repack is complete. Stations may also have the option of selecting a different channel than the one they were assigned in the repack, if they can meet FCC coverage and interference requirements. A tunable mask filter is useful if a future channel change is anticipated.

I didn't expect to see any radical new filter designs at NAB and wasn't surprised, although I didn't have time to visit every exhibit. The major improvements promoted were less insertion loss, easier tuning, and increased power handling capability.

ERI introduced a higher-power model of its UF tunable UHF mask filter. It is now available for operation up to 20 kW (liquid cooled). For VHF, ERI's new VF-H8600 combiner allows two high-band VHF stations to share a single antenna provided they are at least four channels apart.

Dielectric offered air tunable UHF filters capable of handling up to 50 kW air cooled or 30 kW convection cooled.

RFS tunable UHF filters are compact and can be water cooled for operation up to 50 kW. RFS was touting its shipment of a filter/combiner system for KXAS/KXTX in Dallas and its order for the antenna/combiner system to be installed at One World Trade in New York City.

Spinner was showing a product of interest to owners of high-power broadband panel antenna systems. These systems are shared by multiple broadcasters, so detecting anomalies in the line and antennas before catastrophic failures occur is critical. Spinner showed a product that looked like a directional coupler assembly but they claimed is able to detect arcing and connector problems after the power dividers on broadband systems.

Unfortunately, I wasn't able to find any information on it on their web site and Spinner was not willing to reveal how it worked. Another engineer I talked to thought it may work by “listening” for arcs or other disturbances in the line. The system Spinner was showing at NAB was designed for use with 4-inch or smaller transmission line, but I don't see why it couldn't be modified for use with larger line. Based on my conversations with engineers planning high power broadband antenna installations, there is certainly interest in it!

ANTENNAS

Tower structural limits, limited availability of tower crews and equipment, possible zoning/permitting issues and limited resources for designing and manufacturing antennas may reduce broadcasters' options during the short period allowed for transitioning to the new channel. Replacing a top mount stacked slot antenna on a 2000-foot candelabra shared with other stations may be impossible in the time allowed. In such cases, alternatives include using lighter weight, easier to install, side mount antennas or moving to shared broadband antennas.

The good news is that antenna manufacturers are gearing up for the repack by adding staff and boosting manufacturing capacity and providing tools to help broadcasters and their engineers determine what antennas they will need.

ERI announced a deal with T-Mobile that it said will enable it to increase production capacity by 800 percent. ERI had a new broadband VHF panel antenna with a variety of mounting options and a choice of horizontal or circular polarization that should help stations moving to high-VHF. See http://www.eriinc.com/Resources.aspx for information useful in repack planning. I had no problem downloading and installing the ERI Broadcast System Planner V 7.20 on Linux using WINE, although it looks like the software needs to be updated to include the newer antennas.��

Dielectric showed a new lightweight UHF broadband side mount antenna, the TFU-WB, which has 75 percent less wind-load than panels. Azimuth pattern options are limited to two cardioid patterns. Elliptical polarization is available. The antenna's input power rating of up to 60 kW with 24 bays and an azimuth gain of 1.5 or 2.3 (depending on pattern) enable effective radiated power up to the 1,000 kW FCC limit, important if the antenna is mounted lower on the tower.

Dielectric introduced several planning tools, including “Your Guide to the FCC TV Channel Repack”. Dielectric's software for designing antennas is available at http://www.dielectric.com/software/. Once registered, Dielectric's DASP can be downloaded for off-line use or used online. I had no problem using the online version on my Android 5.1 tablet!

RFS presented “Future-proof Antenna Systems” at NAB, outlining some scenarios for the repack, the RF options RFS provides, and some nice photos of the antennas for One World Trade Center and the KXAS/KXTX installation in Dallas.

In this article I've mentioned only some of the more popular companies showing RF products at NAB 2016 that I had a chance to visit and only a few of their products. There are other options for transmitters, filters, and antennas that might better suit your specific needs that you shouldn't ignore.

In my next article I'll cover the ATSC 3.0 innovations at NAB 2016 and the ATSC 2016 Broadcast Television Conference. There's been an amazing amount of progress!

I welcome your comments and questions. Email me at dlung@transmitter.com.

As we start a new year, I thought it would be a good time to take a look at new technology trends. Three areas that attracted my attention are ATSC 3.0 (no surprise), two-way ENG and new technology for wireless microphones. After this year’s spectrum auctions, it’s expected that the number of vacant VHF and UHF channels available for wireless microphones will shrink as TV stations are tightly packed into a limited number of UHF channels and some stations move from UHF to VHF.

ATSC 3.0 ARRIVES
I’ve been writing about ATSC 3.0 for a while, but 2016 should be the year the standard finally arrives. As I’m writing this in late December, there are now six ATSC candidate standards available at www.atsc.org/candidate-standards. Last month the ATSC announced that it was conducting demonstrations of ATSC 3.0 over-the-air technology from multiple companies at CES and I’m also sure the standard will be rigorously tested in the lab and the field this year.

Some of the things I hope will happen in 2016, or soon thereafter, are the start of an FCC process to allow broadcasters to transition to ATSC 3.0; agreements among broadcasters on how to transition to ATSC 3.0 while preserving ATSC 1.0 signals for existing over-the-air viewers; and commitments by transmitter companies to make the equipment to transmit ATSC 3.0 and by consumer electronics manufacturers to include ATSC 3.0 in a range of products. ATSC 3.0 won’t be available to consumers in 2016, but we should see one or more “model” stations on the air to give broadcasters and device manufacturers a chance to demonstrate its capability.

TWO-WAY ENG
ENG crews have gotten used to the convenience of using 4G wireless networks to send stories, live and recorded, from the field to the studio. It isn’t surprising that companies are looking to make newsgathering using broadcasters’ own 2 GHz spectrum just as easy. This will require two-way communication, which could complicate deployment in markets where 2 GHz spectrum is heavily used. Even if the system can work on one channel—perhaps by using time domain multiplexing—other broadcasters are not likely to appreciate having a transmitter on an adjacent channel at popular ENG receive sites.

Silvus Technologies’ MIMO radio As with the transition to ATSC 3.0, it will be essential for broadcasters in a market to work together if two-way ENG is to replace today’s one-way truck to ENG receive site model. Two companies taking two different approaches demonstrated their technology at CCW (now called “NAB Show New York”) last November. Silvus Technologies showed a private MESH network using the Mobile Ad-Hoc Network (MANET) multi-hop IP packet-based wireless networking technology, which they first announced at the 2015 NAB Show. The nodes, which could include a mobile unit on the back of a camera; portable units on the mast of ENG trucks; and fixed units on the roofs of buildings form a mesh where any node can communicate with any other node, even if the data has to pass through other nodes on the way.

JVC camera with MESH transmitter/radio in use There is no need to aim dishes and if nodes can see more than one other node, the system becomes self-healing should one node go down. The Silvus Technologies equipment is compact, making it easier to set up temporary networks for certain events. Additional details are available in this whitepaper: http://pro.jvc.com/pro/pr/2015/nab/JVC_PrivateMESH_WhitePaper.pdf.

Silvus Technologies gear is already being used for military and government operations and has been successfully used to provide live, moving camera coverage from sporting events like endurance races where conventional microwave links break. This may be the year the technology moves into the street for live ENG. The Silvus Technologies website, http://silvustechnologies.com, describes their products and applications.

The Moseley AxxceLTE radios are based on the LTE standard, which could make them a solution for a shared, market-wide ENG system. Conceivably, broadcasters in a community could set up their own LTE network and if it is standards-based, it should work with LTE-compliant radios from other vendors’ LTE-based ENG systems we might see at the 2016 NAB Show. One complication is that LTE requires a management computer to control access and allocate spectrum. I had pictured this as a high-powered server, so I was surprised to see the Moseley Broadcast demonstration at CCW running on a little Linux box.

A bit of Googling found OpenLTE— http://sourceforge.net/p/openlte/wiki/Home. This is an open-source implementation of the 3GPP LTE specifications. With a transmit/receive SDR like the Ettus B2XX you can build your own OpenLTE eNodeB. I hope to have some time to play with that this year and learn more about LTE.

You can learn more about Moseley’s plans for LTE in their 2015 NAB Show press release: http://moseleysb.com/mb/pdf/Ax-cellLTEBAS_PressRelease.pdf.

NEW FREQUENCIES FOR WIRELESS MICS
A hot topic at a meeting last month was the impact of the loss of 600 MHz TV spectrum after the incentive auction on everything from live news coverage to the production of major sporting events and Broadway shows. The analog shutdown resulted in the loss of 18 TV channels widely used for wireless microphones. Anyone using wireless microphones on these channels found them obsolete and illegal.

The same thing will happen after the incentive auction as TV spectrum will again be reduced. Fourteen TV channels will probably go away. If the FCC efficiently packs the remaining VHF and UHF spectrum, there won’t be enough TV channels for the wireless microphones in use today.

Wireless microphone companies are developing products for alternative spectrum— 1.4 GHz and/or 5.0 GHz. A replacement for the analog FM technology used today for wireless microphones will be needed to take advantage of the limited spectrum and provide high-quality sound without dropouts. Swapping out existing wireless microphone equipment will take time, so prudent broadcasters and production companies will start looking for solutions this year.

2016 will be an interesting and challenging year, but new technologies are appearing that will help the broadcasters that don’t sell out in the incentive auction. Look for those technologies in a few months at the NAB Show. I’ll be writing about them in this RF Technology column and on other postings on www.tvtechnology.com.

Comments are welcome! E-mail me atdlung@transmitter.com.

THE BIG ISLAND—The ATSC 3.0 standard is nearing completion. Candidate standards have been released for system discovery, or “bootstrap,” and the physical layer. Broadcast engineers will have to understand how ATSC 3.0 works if they want to take advantage of the improved performance and flexibility it offers. This month, I’ll describe the physical layer differences between ATSC 3.0 and other DTV standards in general and explain the unique ATSC 3.0 bootstrap signal in detail.

Most readers know that ATSC 3.0 uses OFDM (orthogonal frequency division multiplexing), which divides data among thousands of carriers (8K, 16K or 32K); versus the legacy ATSC standard that uses 8-VSB (eight-level vestigial sideband modulation), which puts all the data on a single carrier. All other DTV standards around the world, including DVBT, DVB-T2, ISDB-T, ISDB-Tb and DTMB use OFDM, although DTMB also supports a single-carrier mode.

ATSC 3.0 provides an improvement over existing OFDM-based DTV standards through use of the latest LDPC FEC (low-density parity-check forward error correction) codes and optimized constellations ranging from QPSK (quadrature phase shift keying) through 4096QAM (quadrature amplitude modulation).

Different combinations of codes, pilot patterns and constellations can be selected to allow data rates ranging from less than 1 Mbps in an extremely robust mode working at less than zero dB SNR (signal-to-noise ratio) to over 57 Mbps when a much higher SNR is available.

A key requirement for ATSC 3.0 is the ability to change the transmission format while continuing to support legacy receivers. This is accomplished through a framing structure that includes a “System Discovery and Signaling” signal, referred to as the “bootstrap” signal before each frame. This signal has a fixed physical configuration, but carries data identifying the version of the frame following it. This could be ATSC 3.0, a future ATSC 3.1 or some other variation; even one using a different waveform.

Frames carrying ATSC 3.0 data and those with different formats can be combined in the same RF channel. When it is time to transition to a new standard, the bootstrap will allow older receivers to ignore the new ATSC 3.1 frames, but continue to demodulate the ATSC 3.0 frames.

Fig. 7.10: ATSC 3.0 Frame Structure

Figure 7.10 from “A/322: ATSC Candidate Standard – Physical Layer Protocol” shows the frame structure of an ATSC 3.0 frame. The bootstrap at the start of the frame provides the information necessary to demodulate the preamble, which in turn provides the information necessary to demodulate the rest of the data in the frame and its subframes.

The bootstrap is the most robust part of the signal. The preamble is less robust than the bootstrap, but more robust than the data in the frame.

The bootstrap signal uses a Zadoff-Chu sequence combined with a PN (pseudo-noise) sequence to create a robust signal that allows detection and decoding at a SNR of around –10 dB or less. The Zadoff-Chu root defines the major version number and the PN sequence defines the minor version number. Once this frequency domain sequence is translated to the time domain using a 2048 point IFFT (inverse fast fourier transform), cyclic shifts can be applied in the time domain to encode information in the bootstrap symbol.

The bootstrap signal has a fixed bandwidth of 4.5 MHz, regardless of the actual RF channel bandwidth. The sampling rate is fixed at 6.144 Msamples per second with an FFT size of 2048, resulting subcarrier spacing of 3 kHz.

Each bootstrap symbol has a duration of 500 microseconds. The number of bootstrap symbols is set at four. The first is a synchronization symbol. Symbols that follow contain emergency alert wake-up information, system bandwidth, the minimum time to the next frame with the same major and minor version, and a value for one of the defined preamble structures. Annex K of “A/322” defines 119 different preamble structures.

BOOTSTRAP BENEFITS
Mathematics, beyond the scope of this article, is required to fully describe the bootstrap signal. To learn more, search Google “Zadoff Chu.” See “A/321 Part 1—ATSC Candidate Standard: System Discovery and Signaling” for a mathematical description of how the signal is generated in ATSC 3.0. Zadoff-Chu sequences are also used in LTE cellular transmissions.

The ATSC bootstrap signal provides benefits beyond those I mentioned earlier. In addition to providing a universal entry point to the ATSC 3.0 waveform and any future waveform, the robust signal gives the receiver a head start on frequency offset and RF channel estimation, making it easier to decode the preamble and the rest of the frame.

The bootstrap is integral to reception. The time required to complete a DTV channel scan is a major frustration for viewers. Worse, channel scans often have to be repeated if the desired signal wasn’t received on the first scan and the antenna is relocated. The bootstrap signal should help solve both of these issues. The receiver only has to detect the bootstrap signal to know there is a DTV signal on a channel. The bootstrap signal is much more robust than the payload data, so antenna positioning isn’t likely to be a problem.

The spacing of the frames will determine how long a receiver will have to remain on a channel to detect the presence of an ATSC 3.0 signal. Although the ATSC 3.0 standard will allow frame lengths up to about 5 seconds, such long frames are not likely to be used for conventional broadcasting because it will greatly slow the time required to change programs, even on the same channel.

A more realistic frame length is around 250 ms. At this frame length, a scan of 49 channels would take less than 15 seconds! While this won’t provide the call letters or program information on available stations, that information can be easily obtained after the identified channel is selected, on a more detailed follow-up scan, or from a listing of stations in an area transmitted by one or more of the stations.

The bootstrap signal also will play a key role in emergency alerting. For example, a portable receiver in a tablet or cellphone only has to turn its receiver on long enough to pick up the bootstrap signal (2 ms). The receiver does not need to decode the preamble or the rest of the frame or turn on additional demodulation circuitry until the bootstrap signals that an emergency alert is available, reducing power consumption and thus providing longer battery life. When an alert is received, it can switch on the demodulator and receive and display the emergency message and supplemental data.

The ATSC 3.0 standard offers broadcasters unparalleled flexibility. If broadcasters fail to utilize this flexibility, they may find consumer electronics manufacturers reluctant to support it in their products. Understanding the options is the first step.

Over the next few months, I’ll delve into the ATSC 3.0 candidate standards in more detail and examine some practical examples of how this flexibility can be used. The ATSC candidate standards are available at http://atsc.org/standards/candidate-standards/.

How would you like to see ATSC 3.0 used? How can it increase consumer interest in broadcast TV? Email me atdlung@transmitter.comand I may use your answers in the examples.

See more of Doug Lung’s contributions, including...
November 3, 2015
“Getting Ready for the Repack”
After the FCC incentive auction is complete, likely before we transition to ATSC 3.0, many UHF TV stations will have to move to new channels. Many TV translator stations will have to find new channels, if they can.

July 23, 2015
“Getting Ready for ATSC 3.0”
The amount of spectrum devoted to TV broadcasters is shrinking—from a peak of 486 MHz before 1983 to 294 MHz today.