With the help of a helicopter flying over Las Vegas, Microwave Radio Communications (MRC) will give NAB attendees a chance to see if HDTV's better resolution gives more drama to chopper coverage of police chases, fires, and traffic accidents.
The company will bring in live shots from the chopper's microwave transmission system via a receiver site atop the Las Vegas Convention Center. The system is identical to the one used by KUSA Denver for its nightly newscasts.
The system was born out of MRC's Strata microwave transmitter based on COFDM, says Vice President of Sales and Marketing Dan McIntyre. The use of COFDM improves transmission when the chopper doesn't have direct line of site to the station's antenna.
The development is key for an industry that has been on the hunt for a way to transmit live HD pictures from the field via microwave. McIntyre says that, while KUSA is using the system for its chopper coverage, it can also be employed in an electronic-newsgathering (ENG) van to help ground crews send signals back to the station.
KUSA Chief Engineer Don Perez sparked its creation when he called MRC late last year to see if such a system could be developed. The supplier began working with other manufacturers and Helinet Aviation of Van Nuys, Calif. (which leases the chopper to KUSA) to put it together. "This will allow stations to get HD shots from places they previously couldn't," says McIntyre. "Crews on the ground, for example, won't have to drag wires and cables."
The system demonstrated at NAB illustrates the complexity of the transmission procedure. It sends signals captured in a Sony HD camera into an NEL HD encoder. Then the signal is compressed into the ASI (asynchronous serial interface) format. That allows the HD signal to be sent on MRC's Strata COFDM transmitter at a data rate of 19.35 Mbps. The Strata unit has an HD composite output of 2 GHz, giving it the bandwidth needed to transmit the signal to a high-gain steerable SkyPod V antenna installed under the chopper.
At the convention center, an MRC continuous-rotation UltraScan central ENG antenna will receive and auto-track the 2-GHz RF signal. The antenna is connected to a CodeRunner CR4 central ENG digital receiver that downconverts the signal to a 70-MHz IF signal, which, in turn, is fed into the IF input of MRC's new RXL digital receiver. That unit then translates the COFDM signal into an ASI transport stream, which is then sent to a Tiernan HD decoder, where it is transformed back to a full 1.5-Gpbs video signal. Voila! HD from a chopper on the NAB show floor.
The cost of the Strata unit itself is about $60,000. If stations have the other gear, they can add HD capability to their chopper for that amount. If they're starting from scratch, McIntyre says, the system will cost about $160,000.
Visitors to the MRC booth will also be able to check out a demonstration of a new joint development with Boeing. It enables transmission of uncompressed HD at 1.5 Gbps. That capability is useful when video coming in from a live event has to be edited. And it prevents the problems, such as audio delays, that arise in editing already compressed HD video.
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