Audio Video News

A demonstration of digital television broadcasting in New York City last week may have laid to rest fears about the viability of the Advanced Television Standards Committee's transmission technology. The technique, known as 8-VSB, has been under attack from some quarters, particularly Sinclair Broadcasting, as being inadequate to prevent severe multipath distortion, which results from reflected signals arriving at a receiver slightly later than direct signals. In digital TV, multipath can cause a screen to go blank.

The "blue screen of death," as engineers call it, is one of the biggest criticisms directed at the ATSC standard. Some tests, such as those conducted by Sinclair, have indicated that a more robust transmission technique known as CODFM, adopted for digital broadcasting in Europe, is less susceptible to multipath problems. To the dismay of consumer-electronics manufacturers, who have already rolled out the first generations of new sets, Sinclair and its supporters have called for a review of the ATSC standard. "A change in the standard at this point would be a serious setback to the market acceptance of digital TV," said one Consumer Electronics Association spokesman.

The alarm raised by Sinclair may have been too hasty. Some engineers have noted that early models of receivers were not sufficiently equipped to deal with multipath in highly reflective environments like cities, with their many tall buildings.

Thomson Multimedia may have resolved the issue with its Manhattan demonstration of a new RCA 38-inch HDTV receiver, which picked up and decoded digital signals using only a "rabbit-ears" antenna, available in most hardware stores and RadioShack outlets for $6 or $7. In the demonstration, more than 40 electronics-industry reporters witnessed what PRNewswire called a "stunning, robust broadcast." The transmission was received on the first floor of a mid-Manhattan townhouse from an Empire State Building TV tower. New York City is considered to be one of the nation's worst terrestrial environments for television reception.

"Side-by-side demonstrations of the analog and digital broadcasts provided the most telling evidence that digital television stands to revolutionize broadcasting," the report states. "After a demonstration of DirecTV's satellite-delivered HDTV signals, Thomson showed reporters reception of terrestrial-broadcast digital television utilizing a professionally installed UHF antenna on the roof of a building on West 54th Street in Manhattan. Then, a $6.99 'rabbit ears' set-top indoor antenna was hooked to a television monitor with an NTSC analog tuner to show how difficult it is for Manhattan viewers to watch TV today with an indoor antenna." The result was nothing but "fuzzy ghosting" and a picture "filled with snow."

The report goes on to mention that the same antenna picked up the DTV transmission and displayed it perfectly. "Even in the largest city in America, in a high multipath environment, on the first floor, surrounded by skyscrapers, using an off-the-shelf antenna purchased yesterday—digital TV works like a charm," Thomson senior VP Mike O'Hara said. His company is confident that the Vestigial Sideband (VSB) modulation standard is the "right choice for broadcast transmissions."

"I think you have to question the motives of some in the broadcast industry who may be trying to delay the digital TV transition for their own special interests," he added. With several DTV products already on the market and many more in the pipeline, Thomson and its RCA subsidiary have much to gain from the acceptance of the ATSC standard.