Doug Lung /
04.15.2013 10:59 AM
NAB Show Observations
Solid-state transmitters edging out tube models; attendance up this year
Doug Lung
Over the years I've found I'm spending more time in meetings at NAB and less time prowling for new products on the floor. I did find enough time however to observe some trends while wandering the halls. Last year I described how solid-state RF power amplifiers have been slowly overtaking tubes, even at higher power levels. The trend was obvious this year.

The only high power UHF IOT (Inductive Output Tube) of any type I saw at the show was in the CPI booth. Not too long ago, not only were there tubes on display from multiple vendors, but some transmitter companies showed them in large transmitter cabinets.

While solid-state amplifiers still can't compete with modern MSDC IOT amplifiers in power efficiency, their cost is coming down, making them a viable alternative for applications requiring one IOT and in some cases two IOTs. Although operating cost is likely to be higher than with an MSDC IOT, the reduced amount of maintenance (no high voltage, no tuning, generally stable performance) and simple design (no huge outdoor HV supply, no filament and bias supplies floating 35 kV above ground) can lead to a more reliable, easier-to-install transmitter for stations with a less skilled or resource/time limited engineering staff.

Doherty amplification is the technology allowing solid state amplifiers to take the place of a high power IOT for UHF broadcasting. See my RF Technology article Coming: Higher Efficiency for Higher-Power Amplifiers for an explanation of how it works. Rohde and Schwarz was showing its THU9 Doherty transmitter, first introduced as a prototype last year. Comark introduced its MPTV-8000 series Doherty transmitter that looks like it should be very easy to service.

Liquid-cooled amplifiers can be combined to reach 20 kW RF output or more. Screen Services was showing the same Doherty transmitter it displayed last year. Linear/Hitachi had their Doherty transmitter in operation, sending an ISDB-T signal at a bit less than 2 kW into a dummy load. An AC wattmeter on the power to the amp and an RF wattmeter on the output plotted the efficiency. Due to the use of ISDB-T, the 39 percent efficiency was lower than what could be achieved if they had used ATSC with its lower peak-to-average power ratio. LARCAN and Harris did not have Doherty amplification in their solid-state UHF transmitters (at least not that I could see), but were claiming improved efficiency with 50 volt LDMOS devices.

I noticed manufacturers are starting to see the impact of what has become a real “freeze” on applications to expand TV coverage that went into effect just before the NAB Show. While there may be a short-term boost in sales from stations with construction permits to build out their facilities while they still can (even if they may not be protected in the repacking), reduced U.S. equipment sales is bound to put a strain on TV broadcast transmitter, filter and antenna manufacturers and their employees.

The bad news for broadcasters is that after the repacking is settled and the final channel plan announced, some manufacturers may not survive to meet what could be a huge demand for transmitters, filters and antennas in the three years. Companies may need to focus on international sales to survive until the repacking orders roll in.

Other than the more efficient solid-state amplifiers, I didn't see any new TV RF transmission products that I would consider revolutionary. There were some interesting products that I may cover in a future RF Technology column.

One small item that attracted my attention was the Avateq AVQ1020ATSC ActiveCore RF Layer Monitoring Receiver. This device, which accepts an RF input from −15 dBm to −40 dBm (−20 dBm optimum), provides day-to-day measurement of an ATSC transmitter parameters. Alarms can be set for a variety of parameters and sent using SNMP. The unit uses a Web GUI, making it easy to view detailed transmitter performance at the studio or even over the Internet. The Web GUI provides all common plots for analyzing ATSC RF signals: spectrum, constellation, eye diagram, AM-AM/AM-PM, CCDF, SFN impulse responses/CIR, SNR/MER/EVM variation history, shoulder attenuation history and channel amplitude and phase response. The good news is this until should sell for less than $10k. I found Larcan and Acrodyne/Decontis showing it at NAB. At some point I hope to get one of these to test, and I'll have more on it in a future RF Technology column.

On the Mobile DTV side, there was little new in the transmission area but Dyle was showing the RCA Mobile TV Android Tablet that was demonstrated at CES along with other Dyle-compliant receivers.

I saw the Elgato Android dongle on display for the first time and was able to borrow it to test on my inexpensive Ainol Novo 7 “Flame”/”Fire” tablet. After installing the downloaded APK it ran without incident. I was able to receive the unencrypted stations in Las Vegas and unencrypted UHF stations in Los Angeles. On my way to Chicago, I picked up several mobile DTV channels at the Minneapolis International Airport, although I was able to decode only one of them. The final version will be able to receive encrypted programming. This should be a hit for Elgato if the cross-device compatibility is as good as it appears. (Please note that it must have a USB host mode to work the Android device.)

Upgrades to transmission facilities to improve ATSC Mobile DTV reception without extending contours could help manufacturers during the lull before repacking starts. These could include adding vertical polarization, which will mean higher transmitter power. It could also include low-power on-channel repeaters/boosters for shadowed areas, and perhaps even medium-power transmitters for SFNs, although self-interference to conventional ATSC reception is likely to limit widespread use of ATSC SFNs.

The NAB release with show attendance numbers indicated an increase from recent years—92,414 registered in 2013 compared with 92,708 in 2011. The final show attendance number has yet to be released. In 2012, this was 91,565, down slightly from 91,932, but up significantly from the 88,044 attendees in 2010. (For purposes of comparison, the final attendance figure in 2000 was 115,293.)



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