Tuesday, April 7, 1998 | 1 a.m.
Twenty-six stations have promised the government to broadcast in digital by November, and appear to be on track. They include the ABC, NBC and Warner Bros. Network affliates in Los Angeles and the ABC, CBS and NBC affiliates in the San Francisco Bay area.
Those that didn't make promises have a government timetable to meet. Forty network stations in the top 10 markets are required to start digital by May 1, 1999. But some in New York and Chicago are having trouble finding space for towers.
"The rollout there might be a little slower than anyone had anticipated," said Chuck Sherman, an executive vice president of the National Association of Broadcasters, which is meeting here this week.
As long as they are making a good-faith effort, however, stations with tower or equipment problems can get more time from the Federal Communications Commission.
Eventually, all stations must switch to digital.
Digital technology offers viewers the chance for improved pictures and sound, and even new services. But the digital signal is transmitted over the air into homes just as existing analog signals are and for viewers without cable, that means good reception will depend on where you live.
Among the issues: distance from the broadcasting tower, height of the tower and whether the signal has a clear path or must travel around mountains and tall buildings.
Engineers say if you get a crummy over-the-air picture now, you probably won't get any digital picture unless you have a rooftop antenna. "Rabbit ears" won't do. Most digital TV channels are on channels 14-51 in the UHF band, where it's harder to make indoor reception work.
In analog, a signal weakened by interference can produce a fuzzy or static-ridden picture. But in the digital world, you either get a picture or you don't. It's called the cliff effect.
"The picture is either perfect, or if the signal gets a little bit weaker, it's gone entirely," says Robert Graves, chairman of the Advanced Television Systems Committee, which is helping stations implement digital TV.
Digital signals are more robust and less susceptible to interference than analog. Rain or planes won't degrade the digital signal, but mountains, dense foliage or tall buildings can weaken it if towers aren't high enough, engineers say.
"If you are receiving the digital signal, the odds of it taking a big enough pounding that you'll drop it are kind of low. ... I wouldn't expect it to fade in and out," says Charles Jablonski, vice president of broadcast and network engineering at NBC Inc.
Current rooftop TV antennas can be used to receive digital TV signals, says Jonathan Thompson, spokesman for the Consumer Electronics Manufacturers Association. But a wider range of rooftop antennas is expected along with the introduction of digital TV sets in stores around October, he said.
Some are expected to look like a hockey stick without the hook at the bottom. Others would be similar to round shipping tubes used for posters.
And, if you get your broadcast stations via cable TV - as some 67 million Americans do - it will be up to your cable system to decide whether to use set-top boxes that allow the digital signal to enter your home.
The government also is likely to decide whether cable TV systems must carry broadcasters' digital systems, as they are now required with analog.
FCC Chairman Bill Kennard told broadcasters Tuesday he will watch that issue closely. "No consumer wants to buy five set-top boxes, six remotes and a $6,000 television set that may not work with cable," Kennard said.
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