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.

BELLEVUE, Wash.—T-Mobile has introduced a new 5G-enabled smartphone that uses the 600 MHz it acquired from broadcasters during the spectrum auction held in 2017. The company said it plans to cover 200 million consumers with 5G on 600 MHz by the end of the year.

Pricing and availability for the new limited edition OnePlus 7T Pro 5G McLaren “superphone” will be announced later this year, the company said. T-Mobile says it has been “building toward broad 5G on 600 MHz for two years, laying a foundation with 5G-ready equipment.” The company has been so eager to get its hands on the spectrum that it incentivized some broadcasters—including Dallas’ KXAS—to vacate its spectrum early. The company spent nearly $8 billion to acquire 31 MHz of the 600 MHz spectrum during the auctions, which yielded $19 billion total to U.S. broadcasters.

T-Mobile has already obtained approval from the DOJ and FCC to merge with Sprint, but a lawsuit by 15 state Attorneys General is holding it up.

The company recently released a video showcasing where the 600 MHz channels are showing up, including Cannon Beach, Ore., Bonneville Salt Flats, Utah, Jersey Shore, Pa., Kabetogama, Minn., and Roswell, N.M. 

NEW YORK—CBS Television Stations and T-Mobile completed the repack of WLNY-TV on Long Island and the surrounding area extending into Brooklyn and Queens in early July –more than one year before the August 2019 deadline assigned by the FCC, the companies jointly announced this week.

Clearing WLNY from its 600 MHz spectrum early will enable a more rapid enhancement of T-Mobile’s coverage and capacity in New York City with equipment that supports LTE and is 5G-ready. The company plans to light up 600 MHz LTE service there in early 2019, it said.

“We are happy to report the move of WLNY 10/55 to its new frequency was seamless,” said Peter Dunn, president, CBS Television Stations, a division of CBS Corp. “It was a pleasure to partner with our friends at T-Mobile and be ahead of the curve in terms of serving our viewers.”

[Read: T-Mobile To Help KXAS Move Early]

The early repack of WLNY is the latest accelerated 600 MHz clearing T-Mobile has spearheaded. Others include Fox Television Stations’ WWOR-TV in New York City, and KXAS-TV in Dallas/Fort Worth. Both were relocated at least a year before their FCC repack deadline. T-Mobile has also committed to helping public TV broadcasters by covering the cost of relocating their low-power facilities in rural America.

“The T-Mobile team is deploying 600 MHz LTE across the country at record pace, and we’re laying the foundation for 5G in NYC by deploying 600 MHz with 5G-ready gear,” said T-Mobile CTO Neville Ray.

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

LOS ANGELES—At the Mobile World Congress (MWC) in Barcelona, Spain, at the end of February, T-Mobile announced that it plans to build out its 5G services in 30 major U.S. cities this year, including New York, Los Angeles, Dallas and Las Vegas. While the “Un-carrier” — as the company likes to refer to itself — was not specific about what frequency spectrum those services will use, wireless microphone, in-ear and communications equipment users are already on notice that they may have to vacate the 600 MHz band sooner than the FCC’s post-incentive auction TV station repack schedule would suggest.

T-Mobile acquired 31 MHz of the 600 MHz spectrum licenses made available by the FCC’s Incentive Auction, which ended in April 2017, spending nearly $8 billion. The carrier sought the spectrum because it allows it to “cover every single American with low-band spectrum, which travels twice as far and is four times better in buildings than mid-band spectrum.”

The company has built out its new 600 MHz services quickly, lighting up its first site, in Cheyenne, Wy., in August 2017. By the end of 2017 the carrier had expanded its coverage in what is known in the telecom industry as Band 71 into 26 more U.S. counties.

T-MOBILE OUT IN FRONT

T-Mobile kicked off 2018 with an announcement that its 600 MHz services had been extended to 586 cities and towns in 28 states. The carrier also announced during MWC that it has expanded into 90 more towns and cities across 26 states, including major population centers such as San Jose, Calif., Jacksonville, Fla., Seattle. Louisville, Ky. and Tucson and Mesa, Ariz.

T-Mobile was not alone in acquiring 600 MHz spectrum in the auction, of course, but thus far it is the only carrier to deploy new low-band spectrum services. While the carrier’s initial focus was on building out its Band 71 infrastructure for rural populations, affecting relatively few broadcasters, professional audio companies and other operators, its more recent announcements — and actions — have now put wireless mic users in urban areas on notice.

The carrier’s swift rollout of Band 71 services has put wireless audio equipment operators in “phase zero” of the TV station frequency repack. That term was coined by Karl Voss, Lead Frequency Coordinator for the NFL, for those impacted ahead of the FCC’s planned 10-phase repack schedule.

The potential impact on wireless mic users should not be underestimated. Licensed and unlicensed wireless audio equipment operators must vacate frequency spectrum in the 600 MHz band as soon as any of the new licensees announce an intention to begin using it, whether for testing or full-time services.

The situation is complicated by the fact that Band 71 uplink and downlink spectrum is in 5 MHz blocks to either side of the duplex gap, so does not conveniently line up with 6 MHz-wide TV channels. Per 47 U.S. Code § 503, the FCC may impose a fine of "$10,000 per violation or per day of a continuing violation and $75,000 per any single act or failure to act" on anyone who continues to operate in the relevant spectrum.

According to James Stoffo, founder of wireless comms provider Radio Active Designs, “I’ve done my last show using equipment that operates above 608 MHz, except for the 653-663 MHz duplex gap. If there are no DTV stations in the duplex gap, then we can be assured that those frequencies will remain clean for wireless system usage, as long as the special restrictions for that band are met, until we get a better sense for the RF out of band emissions by the adjacent LTE downlink and uplink.”

If T-Mobile wants to fire up services in an area it can, provided the company sends advance notification to protected users — but wireless mic operators are considered secondary users and are not protected. Happily, the company is bending over backwards to be a good spectrum neighbor, but it can only do so much.

At the DTV Audio Group’s Spectrum Workshop at the SVG Summit in New York in December, Dan Wilson, senior manager spectrum engineering for T-Mobile, encouraged wireless mic operators to visit the carrier’s dedicated website, where it posts updates to the list of new Band 71 sites. The carrier has been notifying its “significant email distribution list” of wireless mic users whenever it updates that list, said Wilson, who is encouraging those not on the list to contact the company. T-Mobile is also working with the SBE and NFL frequency coordinators and, less successfully, with tech companies such as Microsoft and Google and the white space database companies, he reported.

AHEAD OF THE FCC TIMETABLE

Tests conducted by T-Mobile have revealed several scenarios in which the carrier’s equipment and wireless mics can interfere with each other, Wilson reported. In the uplink spectrum, the wireless mic will cause interference to the T-Mobile base station. In a venue, a wireless handset could cause interference to a wireless microphone receiver.

In the downlink spectrum, wireless mic interference directly into handsets is a concern, he said. The downlink base station into the wireless receiver is also a concern.

Each downlink receiver is 40W plus the antenna gain, he noted. Anyone doing frequency scans will immediately see T-Mobile’s downlink, which is active 24/7, he said, but handset use will depend on customers in the venue.

Wireless mic operators should not assume that the TV station repack will follow the FCC’s timetable, said Wilson. “We are working with stations to move them earlier than the 10-phase plan.”

T-Mobile previously announced that it had partnered with Fox Television Stations to assist in repacking its 600 MHz spectrum. The carrier has also partnered with PBS and America’s Public Television Stations (APTS) to assist rural translators in the move to new airwaves, clearing the spectrum for its Band 71 services.

As part of the Fox agreement, WWOR-TV in New Jersey will repack in early 2018, more than one year sooner than the originally scheduled FCC deadline of August 2019. According to Wilson, T-Mobile won licenses to 622–632 MHz in the downlink spectrum (663-673 MHz in the uplink block) in the New York metro area and will begin services in Manhattan in Q3 2018 after assisting WWOR to relocate.

Wireless audio equipment operators in New York City will be affected if they are using those uplink block frequencies but will initially not see a lot of uplink activity since there are currently only two 600 MHz handsets on the market, he said. However, Wilson added, T-Mobile plans to launch more than a dozen new 600 MHz-capable smartphones in 2018.

In short, wireless mic users can’t rely on the FCC’s projected 39-month transition plan to replace affected equipment with gear compliant with the new rules. The bottom line? Start budgeting for replacement equipment and begin replacing that equipment now.

OLD LYME, CONN.—The FCC has set a deadline for wireless microphone manufacturers to cease operation in the 600 MHz band, so as a result Sennheiser is providing its customers an opportunity to trade in their equipment that would be affected for new gear.

Between now and Dec. 14, owners of any non-compliant wireless systems from any manufacturer can trade it in for the latest Sennheiser FCC-compliant equipment through a special rebate program.

There are three steps to the rebate program. Step one, equipment owners should check eligibility for the rebate by checking for a printed sticker on the equipment that indicates its operating frequency range; anything above 608 MHz will require an upgrade to maintain FCC compliance. Step two, consumers may purchase authorized wireless equipment from an authorized Sennheiser dealer. Step three, consumers will send the outdated gear to Sennheiser.

Here is the list of eligible products for the promotion: XS Wireless Series; evolution wireless D1 Series; AVX Series; evolution wireless we 100 G3 Series; evolution wireless ew 100 G3 Portable Series; evolution wireless ew 300 G3 Series; evolution wireless ew 300 IEM G3 Series; evolution wireless ew 500 G3 Series; SpeechLine Digital Wireless Series; 2000 Series; 2000 IEM; 3000/5000 Series; Digital 6000.

WASHINGTON—The Federal Communications Commission today announced that it has accepted 2,319 applications for the 600 MHz spectrum sold off in the spectrum incentive auction. The applications comprise those licenses sought by 11 out of 50 total bidders and represent the first tranche of applications, according to an FCC spokesman, who said the “more complex bidding credit applications tend to take longer to accept for filing.” 

The bidders with applications accepted among this first tranche include the following providers, followed by the number of licenses applied for and the amount each one bid in the forward auction according to the April 6, 2017, bidder summary:
· T-Mobile, with 1,525 license applications ($8 billion);
· ParkerB.com Wireless, Dish Network’s bidding entity, with 486 ($6.2 billion);
· U.S. Cellular, of Chicago, with 188 ($329 million);
· CC Wireless Investment, Comcast’s bidding entity, with 73 ($1.7 billion);
· AT&T Spectrum Holdings, with 23; ($910 million);
· Pine Belt Cellular, an Alabama-based provider, with nine ($1.8 million);
· Docomo Pacific, a wholly owned subsidiary of Japan’s NTT DoCoMo., with six ($3 million);
· Plateau Telecommunications with five ($1.4 million);
· LICT Wireless Broadband of Rye, N.Y., a regional and competitive local exchange carrier, with two ($686,000);
· NEIT Services, a Monona, Iowa, phone company, with one ($481,000); and
· Polar Communications Mutual Aid Corp., of Park River, N.D., with one ($62,500).

The commission emphasized that these applications have been accepted but may still be rejected: “The commission may return or dismiss any application if it is found, upon further examination, to be defective or not in conformance with the commission’s rules.”

Petitions to deny the applications must be filed no later than May 30 2017—ten days after the date of today’ Public Notice. Oppositions to those petitions must be filed no later than June 6, 2017, five business days after the filing date for petitions to deny.Replies to oppositions must be filed no later than June 13, 2017, five business days after the filing date for oppositions.All pleadings filed regarding a 600 MHz long-form application should reference the file number of the application.

The license application file numbers can be found on Attachment A of the Public Notice. (Attachment B is the same information, sorted by market.)

Fig. 1: Operating at 17.2 kHz, the Alexanderson alternator rotating armature radio transmitter at the Varberg Radio Station at Grimeton near Halland Sweden is the only one of its type in the world.

THE BIG ISLAND—To understand the concerns about spectrum availability and the value of spectrum, it’s worth taking a look at the history of spectrum usage, how spectrum is valued, and what the impact of the demand for greater wireless data bandwidth and associated spectrum needs will have on broadcasting.

WHAT SPECTRUM IS MORE VALUABLE?
The UHF TV spectrum at 600 MHz has been called “beachfront property” for wireless carriers but before buying that property, it might be worth asking if today’s “beachfront property” might be underwater tomorrow. Looking at the history of spectrum usage, could this spectrum be worth less in 2020 than it was when the National Broadband Plan was released in 2010? This month I’ll present some historical data and some technical arguments that support my assertion that, as demand for data bandwidth increases, the value of higher frequency spectrum increases and that of lower frequency spectrum decreases.

It may be hard to believe, but at the dawn of the 20th century frequencies below 1 MHz were considered the best ones for communications. Large RF alternators were used to generate high power RF signals at frequencies below 50 kHz. One is still operational on 17.2 kHz (Fig. 1). Amateur radio operators were disappointed when the Radio Act of 1912 restricted private radio transmission to wavelengths above 200 meters (1500 kHz), but found the higher frequencies actually allowed longer range contacts.

In the last 100 years, amateur radio operators have found their higher frequency allocations, well into the GHz bands, limited or shared as other users discovered the value of their previously undiscovered higher-frequency spectrum.

I got my first job in broadcasting more than 45 years ago and at that time AM radio (540–1600 kHz) was king and FM radio (88–108 MHz) was a stepchild that got little respect. Today, except for a few stations in larger markets, listeners tuning into AM radio are likely to hear the same programs (usually sports talk) delivered nationwide by satellite. Programming has moved to FM, and even all-news AM stations are finding outlets on FM radio, if not as the primary service, as a digital HD-Radio sub-channel.

After the transition to digital TV, even the FCC recognized that UHF spectrum was at least equal to VHF spectrum. Based on the incentive auction rules, UHF TV spectrum is now valued significantly higher than VHF TV spectrum. History shows that through time, higher frequency spectrum becomes more valuable, although the technical and economic reasons for that vary.

THE LIMITS OF SHANNON
Fig. 2: Comparison of distance-based path loss models with unity gain antennas. The curves labeled “Empirical NYC” are the experimentally derived mmW models based on the NYC data. These are compared to free space propagation for the same frequencies and the 3GPP UMi model for 2.5 GHz.
Let’s look at the technical reasons first. In my article “Reviewing Next-Generation Error Correction Codes,” I explained the “Shannon Limit,” the maximum error-free data rate that could be sent over a given amount of bandwidth for a given signal-to-noise ratio (SNR). The obvious conclusion is that more bandwidth provides a greater data rate for a given SNR. The lower the frequency, the lower the available bandwidth.

Designing RF systems that can use bandwidths more than 5 percent of the center frequency is difficult. At 600 MHz this equates to 30 MHz; at 5 GHz this equates to 250 MHz—more than eight times the bandwidth and eight times the data rate for a given SNR. This makes higher frequencies more useful. If someone tried to put a 200 kHz-wide FM signal in the medium wave AM band, there would have only been room for five stations! Wider bandwidths and higher speeds demand higher frequencies.

Some of you may be asking, “What about MIMO and directional antennas?” The advantage again goes to the higher-frequency spectrum. The reason is that the directivity of an antenna is related to its size in wavelengths. For MIMO to be effective, it requires at least two receive antennas isolated from each other. The longer wavelengths (lower frequencies) in the UHF or lower bands make it more difficult to isolate antennas, especially in the confined space of smartphones and even tablets compared to higher-frequency spectrum. One wavelength at 600 MHz is about 20 inches, while at 5 GHz, the wavelength is less than 2.4 inches.

One of the advantages of lower frequencies is that they can travel great distances. I regularly receive KNX (1070 kHz) from Los Angles after dark while driving in Hawaii. Properly designed UHF and VHF stations, assuming no terrain obstructions, can provide a decent signal all the way to the radio horizon. Lower frequencies are also passed through foliage and through windows. This ability to get indoors, to get through the trees, is one reason 600 MHz spectrum has attracted the interest of wireless carriers. However, Shannon’s Limit still applies, limiting the number of users a site can support. As the number of users grows it will be difficult to increase the bandwidth, and thus the data rate, enough to accommodate them, even after using directional antennas to provide sector coverage.

FREQUENCIES OR SITES?
As cell sites become overloaded, wireless carriers increase capacity by adding more sites, so each one serves a smaller number of customers. As the service area of each site is reduced, the long-range coverage of UHF frequencies becomes less important and limiting interference more complicated. We’ve already seen Verizon shift traffic from its 700 MHz LTE spectrum to its 1700 MHz spectrum in urban areas. As demand for bandwidth grows, even reallocating the entire UHF TV band for wireless broadband won’t be sufficient.

With a large number of closely spaced cell sites, there is no advantage in using UHF spectrum (500–800 MHz) for wireless broadband. As sites become denser, it is easier to move to higher frequencies with wider RF bandwidth. More bandwidth equals higher data rates and more users. At much higher frequencies with shorter wavelengths, it’s possible to use massive MIMO with very directional beams. Researchers at NYU Wireless (an academic research center focusing on wireless, computing and medical applications), have successfully tested wireless links in New York City using 28–60 GHz spectrum. Last fall, Samsung tested 5G technology in New York as well, delivering data rates more than 1 Gbps over distances up to 2 km using 28 GHz spectrum.

Who will be the winner in the battle for wireless bandwidth? Look at companies developing technology for spectrum well above that commonly used today. The need for more base stations will benefit those companies with the ability to inexpensively deliver very high data rates to antennas on roof tops and light pole tops.

Cable companies are in a great position to move their business from delivering fast, wired Internet to delivering wireless Internet just as fast or faster. It isn’t surprising CableLabs has joined NYUWireless.

Another option—if some data bandwidth can be sacrificed—is a mesh network, where base stations connect to each other to move data across the network. Such a network could be built inexpensively using unlicensed spectrum, similar to Metricom’s 900 MHz Ricochet network that, until it shut down in 2001, provided higher data rates than most cellular companies could provide.

What about broadcasters? The maximum frequency allocated for conventional TV broadcasting is 698 MHz and that may drop to 608 MHz or less after incentive auction repacking. Being limited to 6 MHz of bandwidth, the only way broadcasters will be able to deliver higher data rates and prettier pictures to viewers will be to move to a new transmission standard. ATSC 3.0 will allow broadcasters to trade-off robustness for and increase in the data rate and that loss in robustness can be offset by building single frequency networks—multiple transmitters using the same channel—to deliver a stronger signal to viewers unable to get a strong signal from the main transmitter. Such coverage could still be useful after 5G technology allows essentially unlimited wireless Internet.

I welcome your comments. Email me atdlung@transmitter.com.

Want to learn more about how the upcoming spectrum auctions will impact your business? Be sure to attend "Spectrum Auction Preparation: What You Don't Know Will Hurt You," Thursday, July 23 at 2:30 p.m., EST.