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Help File: After the DTV Switch, Some Tinkering Still Required

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By Rob Pegoraro
Sunday, June 21, 2009

QTwo weeks ago, you suggested that digital-TV reception would improve after analog broadcasts ended. But the DTV signals of channels 7 and 9 seem to have gone off the air.

AWhen ABC affiliate WJLA and CBS affiliate WUSA moved their DTV channels from UHF (ultra-high-frequency) airwaves to the VHF (very high-frequency) spaces once occupied by their analog broadcasts, many formerly-happy viewers found they could no longer get those stations -- contrary to predictions of improved reception from such sources as the Federal Communications Commission.

This wasn't just a matter of people using UHF-only antennas or forgetting to have a TV or converter box re-scan the airwaves for the new frequencies. I know, because I've had trouble picking up these stations with a VHF/UHF antenna, even after many re-scans.

Viewers in other cites with UHF-to-VHF digital switches have reported similar issues.

The problem seems to be rooted in the complex interactions of broadcasts in the VHF band with other signals and buildings in the way. Fixing it may require tinkering with your antenna.

First, try moving the antenna, if it's an indoor model. Parking it closer to a window seems to help a lot.

Second, consider swapping it out for a more traditional design. WUSA's director of technology and operations, Victor Murphy, wrote in an e-mail that "new 'space-age' antenna configurations like flat panel antennas, etc., don't perform as well as we'd like." Instead, he recommended "dipole" antennas -- old-fashioned rabbit-ears -- for better VHF reception. WJLA's Web site seconds much of that advice.

Murphy further suggested extending the "ears" of a dipole antenna only halfway to two-thirds out and then laying them flat, parallel to the ground. If the antenna is amplified, try turning off that signal booster. Replacing the cables running from the antenna to the TV can help as well.

But if you live more than, say, 10 miles from the TV transmitters, the most effective fix may be to upgrade from an indoor antenna to an attic- or roof-mounted model.

Rob Pegoraro attempts to untangle computing conundrums and errant electronics each week. Send questions to The Washington Post, 1150 15th St. NW, Washington, D.C. 20071 or robp@washpost.com. Visit http://voices.washingtonpost.com/fasterforward for his Faster Forward blog.


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