Will digital TV reception problems doom broadcast TV?August 5th, 2005
For viewers, digital TV may offer the best TV reception ever—or none at all.
With over-the-air analog TV, when interference strikes, ghosts may haunt your picture, and reception gradually degrades over distance. Digital TV pictures are different: they remain perfect as long as an acceptable signal can be received. But if the signal is too weak, sound and picture disappear entirely. This can be a particular problem in fringe areas. Viewers who live a long way from a broadcast tower and get so-so pictures on an analog set may have trouble getting digital broadcasts at all.
Such problems are not limited to outlying areas. A city dweller who lives a mile from the transmitter can have trouble picking up a digital signal that bounces off of tall buildings in its path, as detailed recently in Scientific American:
I had stumbled headlong into the problem identified in the late 1990s by the Sinclair Broadcast Group, based near Baltimore. The company conducted field tests suggesting that indoor reception may not be possible.
The U.S. transmission format is called 8-VSB (for 8-level vestigial sideband), which is more susceptible to multipath distortion than the European system, called coded orthogonal frequency division multiplexing, or COFDM. The 8-VSB format requires less power to broadcast and packs in more data each second (19.4 megabits compared with 18.66 for COFDM)–useful for “datacasting” services. But 8-VSB did so poorly in multipath environments that Sinclair urged the FCC to switch.
After spending $300 on a set-top box, the writer struggled with three different antennas, including a bulky rooftop antenna used indoors. Improved receivers and antennas may eventually minimize these sorts of reception issues, he suggests, noting that advances in receiver circuitry led Sinclair (not my favorite broadcaster, incidentally) to withdraw its objections to the U.S. digital transmission format. Some advances have yet to reach the consumer market, however.
These problems may be nothing more than growing pains, recalling those faced in the early days of analog TV. Even as late as the 1970s, most viewers had to use rooftop antennas or fiddle with rabbit ears and TV-tuning dials to get a decent reception.
But this is not an isolated incident. More than a few techies who have embraced HDTV report problems picking up a signal. So what are the chances for the average viewer? And while the FCC has instituted the requirement that larger sets include digital tuners, how many of today’s tuners will be up to the task?
For members of Congress, cable or satellite is a must—how else can you watch yourself on C-SPAN? But millions of Americans, especially those of limited means, still depend on over-the-air TV for entertainment, news and emergency information. As we look toward the phase-out of analog broadcasts, we must face up to this question: How ready is America to switch to digital TV?
• Source: Scientific American