Poor Quality of DTV Receivers Noted by Disney in DTV Review Replies
Disney cited FCC findings that commercial DTV receivers aren’t up to snuff, in reply comments it filed last week in an FCC review of the DTV transition. In late March, the FCC Office of Engineering and Technology found that of the commercially available receivers it put through an interference rejection threshold study none met ATSC guidelines that are more lax than the “receiver performance assumptions on which current DTV interface protection criteria are based.” For Disney, that means New York viewers may have problems picking up a DTV signal from its WABC-TV New York station, it said. It asked the commission for leeway for Zone I VHF channel stations like WABC-TV to reach private interference agreements with other broadcasters.
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Among variances OET found between commercial DTV tuners and its own receiver performance assumptions was that no DTV tuner tested had a double-conversion tuner. However, such a tuner was used in the prototype DTV receiver on which the “Grand Alliance” based interference protection criteria for the DTV channel allotment process. Single-conversion tuners, like those found in the commercial DTV receivers OET tested, are more susceptible to interference.
The specs for subsidized digital-to-analog converter boxes don’t involve a double-conversion tuner, said David Donovan, president of the Association for Maximum Service TV. The receivers normally work fine and DTV receivers will improve over time, but the OET report showed how vulnerable DTV sets are to interference from so-called white-spaces devices that may be used to offer wireless broadband, he said. Based on the FCC report, even if white spaces sensing technology worked “and these guys operated on the first adjacent channel, they will cause interference on 80 to 87 percent of the service area,” Donovan said.
That’s a message broadcasters likely will have to take to Congress this month, with white spaces bills pending in the House and the Senate. “We're working hard on that issue in trying to get this message out there, that America’s DTV future is at stake,” Donovan said. “We hope that the Congress and the FCC are concerned enough with the DTV transition and the nearly 19.6 million homes that rely on over the air TV, that they won’t gamble away their DTV future.”
The FCC should proceed cautiously with its white spaces rulemaking as the DTV transition nears, engineering consulting firm Cohen Dippell and Everist said in reply comments. “To do otherwise would add additional uncertainty to a very complicated process which has been mandated by law and which the Commission has only limited resources to respond,” it said.