Doug Lung The number of exhibiting transmitter companies and the size of their booths were smaller at the NAB Show this year than in years past, reflecting the impact of how U.S. TV broadcasters will respond to the incentive auction before upgrading their transmission facilities. That doesn’t mean they’ve been standing still.
Transmitter manufacturers are continuing work on improving solid-state high-power amplifiers using Doherty technology. Antenna and passive RF system equipment manufacturers are working on broadband antenna technology and development of tunable transmitter mask filters for low- to high-power applications.
As ATSC 3.0 approaches candidate standard status, exciter manufacturers were showing products that can be upgraded via firmware to support ATSC 3.0, provided there are no major changes from the current baseline.
Dektek DTU-315 All-standard All-Band USB 3.0 modulator One piece of good news this year was the return of Larcan to the exhibit floor, although it was in the booth of Unique Broadcast Systems (UBS), the purchaser of the Larcan’s intellectual property. Time will tell how well UBS will support Larcan, but I was pleased to see Larcan employees in the UBS booth actively promoting Larcan. It appears UBS will not only be supporting previously sold Larcan gear, but will relaunch many of the popular Larcan product lines.
Another bit of good news was that Comark, now 100-percent owned by Hitachi, is continuing support of its popular DCXP Paragon transmitters using the L-3 MSDC IOT. While MSDC IOT sales have slowed, if not stopped, Comark engineers have made improvements in cooling system efficiency to help the Paragon hold its position as a UHF high-power amplifier with system efficiency equal to or greater than the best solid-state Doherty amplifiers.
Comark is still working on its high-power UHF Doherty transmitter and had an amplifier module on display. It looked solid on the outside, but Comark wasn’t opening it so I couldn’t tell for sure if there was anything inside. The control interface looked promising and Comark is requesting comments on features from potential customers. Hitachi holds many patents on Doherty technology and I wouldn’t be surprised if the Comark transmitter, when released, offers performance and efficiency equal to or better than that available from other manufacturers. While I was quite impressed with the design, I had to remind myself that a product that’s still in development often has wonderful features and performance that disappear when the final product appears. We should know next year how wonderful it is.
GatesAir has already shipped high-power solid-state Maxiva ULXT transmitters with power outputs up to 60 kW. The design of the amplifier trays and combiner assembly make it easy to configure the transmitter for a range of power outputs. While the high-power amplifiers are liquid-cooled, they are powered by reliable telecom-grade air-cooled GE switching power supplies, the same ones Comark was showing with its prototype amplifier. The power supplies are paralleled to provide some redundancy in case one fails. The first GatesAir Doherty amplifiers, while far more efficient than conventional solid-state amplifiers and competitive with conventional IOT efficiency, were not as efficient as the Rohde and Schwarz solid-state Doherty amplifiers. GatesAir admitted they were still working on the design of the Doherty amplifiers and that the next version would have much better efficiency.
One trade-off transmitter manufacturers have to make when designing high-power amplifiers is whether to sacrifice efficiency and build broadband amplifiers that work over the entire UHF band or maximize efficiency using narrower band amplifiers that only work over a portion of the UHF band. The difference in efficiency can be significant at higher power levels. While many broadcasters who purchase transmitters before the repacking will have to change channels in a few years, it is unlikely they will be changing channels again unless the transmitter is taken out of service and shipped to another station. Swapping or retuning out a hundred or more amplifier pallets is time-consuming, but the energy savings over the life of the transmitter should offset that one-time headache.
PREPARING FOR ATSC 3.0
Even more good news—TV exciter manufacturers are preparing for ATSC 3.0! Comark, Teamcast and One Media joined together to show a working system based on One Media’s ATSC 3.0 proposal. The Teamcast exciter can provide an ATSC 1.0 signal today and, when the ATSC 3.0 standard is finalized, be updated via firmware to transmit ATSC 3.0. Anywave was also showing a programmable exciter that should be able to be upgraded for ATSC 3.0. While you may not be familiar with Teamcast and Anywave, their exciters are often relabeled and used in other manufacturers’ transmitters. If the Comark/One Media demo at the NAB Show is any indication, the new Comark transmitter may be using the Teamcast exciter.
At the NAB Show Futures Park, ETRI, CRC and the University of the Basque Country (a Spanish public university) demonstrated the LDM system I wrote about two columns ago. GatesAir was showing the multimedia emergency alert system proposed by LG, Zenith and GatesAir for ATSC 3.0 in the GatesAir booth. China’s National Engineering Research Center (NERC) has been active in the ATSC 3.0 process and had a demo in the ATSC Pavilion.
My biggest “find” was a pocket-sized signal generator from Dektek that connects to a USB 3.0 port and is capable of generating ATSC, ATSC-MH, DVB-S (multiple versions), DVB-T, DVB-T2 and other popular transmission standards. I was told that when the ATSC 3.0 standard stabilizes, it will be available as well. The base unit with a few core transmission standards costs around $2,600 while a fully loaded unit with all available standards will cost around $6,000. While I doubt this device will match the specifications of the Rohde and Schwarz SFU, it will provide a relatively inexpensive way for broadcast engineers and equipment manufacturers to become familiar with ATSC 3.0 while testing stream generation equipment and receivers.
While at the NAB Show I was frequently asked about the future of TV broadcasting in the United States. After discussions with other broadcasters and manufacturers, I’m guardedly optimistic. Broadcasters will have to make some tough decisions over the next three to five years if over-the-air TV is to survive. More on that in my next article.
Does over-the-air TV have a future? I welcome your opinion. Send me an email at email@example.com.
Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.
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