Auto-detect function soothes 2GHz digital ENG compatibility worries
Jun 9, 2009 12:15 PM, By Phil Kurz
Sprint Nextel’s latest bimonthly update to the FCC showing steady progress on the 2GHz Broadcast Auxiliary Service relocation project means many station engineers are entering a period outside of the old, familiar ways of doing live reports from the field.
Recently, one Broadcast Engineering reader wrote to find out if a consensus is emerging in the industry about the most commonly used configuration parameters for the new digital radios being employed as part of the relocation. The readers asked, would it be desirable for the industry to use the same configuration for modulation, forward error correction, guard band and pedestal?
After all, having a consensus might help news crews, stations and networks in several respects, including sharing signals for pool feeds of certain events, avoiding interference problems and making coordination easier, he reasoned.
A series of calls to various industry authorities has revealed that there is no industry consensus, but that lack of consensus has played into the design of ENG receivers, which in turn should allow most stations to sidestep any problems. Recognizing there was no industrywide agreement, many RF vendors are building receivers with auto-detect functions that will tune the receiver using the parameters appropriate for the signal detected.
“From our standpoint, because there was no consensus, the radios are all auto-detectable regardless of modulation,” said John Payne IV, VP of engineering at Nucomm. “Typically, the receivers will automatically track what the transmitter is doing.”
Leo Rosenberg of Direct Broadcast Services, and the SBE frequency coordinator for New York City in frequencies 1GHz and higher, agreed. “Generally, many of the broadcasters, will use many of the same parameters, but there is no official consensus,” he said. “Any given station can determine its own parameters.”
While automatically detecting and identifying the parameters of the 2GHz digital BAS transmitter is helpful, broadcasters should keep in mind that at least one proprietary modulation technique is being employed in the industry and may not be automatically detectable by equipment from another vendor.
“LMS-T modulation is proprietary,” said George Maier, director of product marketing and management at Microware Radio Communications. LMS-T, developed by MRC sister company Link Research, would not be automatically detectable today, he added. However, MRC is building its own receivers to detect LMS-T automatically and demodulate it, Maier said. (MRC and Link Research as well as Advent Communications recently began operating as a unified company under the name Vislink News and Entertainment.)
On the horizon is another aligned issue: HD electronic newsgathering. As broadcasters increasingly integrate HD into their field acquisition, it’s likely the number of instances of incompatibilities between encoders and decoders will rise, particularly with MPEG-4 AVC H.264 gaining popularity for HD contribution. “More and more HD is being done in the field,” Payne said. “If you do a pool feed, everyone who needs to receive that signal needs to be on the same encoding standard and format.”
However, despite a couple of potential hiccups, it appears the auto-detect capabilities being built in to the digital 2GHz ENG receivers make forming an industry consensus unnecessary.
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