Most broadcast engineers probably remember the intense debate about the performance of the European DVB-T COFDM-based DTV transmission standard versus the U.S. ATSC 8-VSB-based system. Nat Ostroff, vice president of New Technology for Sinclair Broadcast Group was one of the most vocal and persuasive critics of the performance of 8-VSB for indoor and urban TV reception. He conducted numerous public demonstrations and field tests to support the criticism. In the years since those tests, manufacturers have worked to improve the performance of 8-VSB receivers, especially in the presence of multipath. The latest demodulators are able to use energy in the multipath echoes to allow reception even when the signal-to-noise ratio of the main signal alone is below the 8-VSB threshold level. A press release entitled, "Sinclair Broadcast Group Pleased With Progress in DTV Receiver Technology," issued last week by Sinclair, should put to rest broadcasters' concerns about the performance of 8-VSB.
"We are pleased to see the progress made by Zenith that will allow consumers to easily receive free digital television broadcasts in their homes," Ostroff said. "Broadcasters and consumers can now look forward to a robust DTV service delivered over-the-air without having to subscribe to cable or satellite."
"Our concerns that poor indoor reception would hinder the DTV transition have now been addressed," he said. "And this is especially timely because of the FCC-mandated rollout of millions of large-screen HDTV receivers with integrated over-the-air tuners beginning this summer. With indoor reception now more viable, broadcasters need to examine their current transmitting power levels to assure that they deliver an adequate signal inside the home, and consumer electronics manufacturers need to ensure that breakthrough technologies such as this are available in the market."
Sinclair and Zenith conducted informal field tests in Baltimore to see how well the fifth-generation receiver worked at locations sites Sinclair previously identified as having difficult multipath conditions. Early generations of receivers had trouble at many of these locations. The sites included parking garages and sidewalk locations, many without direct line-of-sight to the transmitter site.
The press release said, "results of the new trials show dramatically improved reception with the receiver built around a new DTV chip developed by LG Electronics Inc., Zenith's parent company. Specifically, the innovations in the fifth-generation integrated circuit allow it to lock onto signals in severe multipath environments, even when the ghosts have long delays or are larger than the main signal."
Sinclair said fifth-generation receivers will be able to tune in multiple digital signals using simple indoor antennas without having to change the orientation of the antenna.
For articles I wrote about the COFDM versus 8-VSB debate, refer to the back issues of my RF Technology columns at www.tvtechnology.com.
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