Storm brewing

时间:2019-03-07 02:12:04166网络整理admin

By Paul Marks TV BROADCASTS warning of approaching hurricanes or tornadoes, or other civil emergencies, might not reach American homes when digital TV becomes the norm, according to video experts at the Pentagon. This claim puts one US government agency at loggerheads with another in the acrimonious debate over standards for digital TV. Stephen Long, chairman of the Department of Defense Video Working Group, has called on the Federal Communications Commission to conduct a public debate questioning the “continued use” of the digital TV standard set by the FCC in 1997. Long believes the standard, called 8VSB, could prevent emergency communication with large sections of the public. “There is growing evidence that digital TV receivers using 8VSB may require large, highly directional outdoor antennas for adequate signal reception,” Long says. Such antennas, he points out, may be the first things destroyed in storms or other disasters. But Robert Graves, who heads the FCC committee that set the standard, claims that Long is basing his assertions on “scientifically unsound” test data from a group of commercial TV stations who want the FCC to let them use a rival standard called COFDM—which delivers digital TV in Europe (New Scientist, 30 October, p 23). The rebel broadcasters—led by the Sinclair Broadcast Group of Baltimore, Maryland—say their tests show 8VSB only works well with TVs using large outdoor antennas. They say that indoor set-top antennas and portable TVs have trouble coping with signal echoes from buildings and vehicles, which blank out the picture. But the COFDM standard uses echoes to reinforce the picture signal, so set-top and portable antennas still work. Graves dismisses the rebels’ criticisms. He claims that Sinclair’s engineers did their tests in unusually difficult locations using the “worst 8VSB receivers on the market”. Newer 8VSB receiver technology shows “dramatic improvements”, Graves says. The Pentagon, however, believes that COFDM could improve reception of both standard and emergency broadcasts. Nat Ostroff, Sinclair’s technology chief, says: “The entry of the Department of Defense on the side of COFDM is very helpful in raising the legitimacy of our position. They represent a truly independent evaluator.” But the two sides will eventually have to agree the best way to handle emergency broadcasts in the digital age. The National Hurricane Center in Miami says TV remains the best warning medium. Its spokesman Frank Lepore says: