DTV Signal Problems Hard to Anticipate, Officials Say

One issue is that stations using the lower part of the VHF band have needed to increase power, said several industry officials. Even stations using UHF frequencies -- thought by some to be better suited for DTV -- have viewers close to their antennas in buildings often built of concrete where digital signals don’t penetrate as well as analog, others said. Broadcasters are using the post-transition experience to try to address such issues, some of which seem to have to do with digital set-top boxes having problems processing signals and viewers using indoor instead of outdoor antennas, they said. FCC Chairman Julius Genachowski and his colleagues will get a DTV status update at today’s commission meeting (CD July 1 p8).

One client of lawyer Robert Rini increased power, but “it only had a marginal impact on the fringe area we were hoping to improve, but it did help in the core area,” he said. “I think the jury is still out on how these DTV signals are propagating” as “people are still trying to understand it better,” he said. One broadcast lawyer said he'd heard of problems in “concentrated urban areas” such as the Chinatown section of San Francisco.

But Valari Staab, general manager of Disney-owned ABC affiliate KGO San Francisco, said she'd heard of no problems with broadcasters having signal difficulty in the Chinatown area. There have been reception problems in the Bay Area, mainly because of geography and in places such as “in the shadows of hills,” Staab added. “We haven’t had much unexplained” signal issues. That sentiment was shared by executives at Gray TV, Scripps and Media General, which own a total of more than 50 stations.

The FCC is aware there’s some variability with digital signal propagation, but hasn’t had many reports of unexplained problems and is working to solve all issues, said three agency officials late Wednesday. Viewers had “many years” to fix analog problems, such as snowy pictures, or simply put up with it, said Chief Julius Knapp of the Office of Engineering and Technology. “You've got a system that’s complex -- it’s just been a short time since we've instituted it,” he said. “Just as there are dead spots where you have trouble getting cellphone service, the same thing happens with TV.”

There are some “individualized” issues at TV stations, said an FCC spokesman. The commission has sent about a dozen engineers and other staffers to Atlanta, Chicago, Miami, New York, Philadelphia, Nashville and several other large markets to work on the problems, he said. “Our challenge is to figure out where unique signal or reception issues are.”

Frank Jazzo, also representing TV stations, “knew there was a major problem” when speaking in May in New Orleans at the Louisiana Broadcasters convention and a station there had already gone all-digital, moving to a VHF channel, couldn’t be received in many places in the city, he said. “New Orleans is extremely flat with few high rises, other than downtown, so it should be best-case from a propagation perspective.” Broadcast lawyer Henry Solomon has heard of viewers having difficulty getting high-band VHF channels using indoor antennas, but outdoor antennas seem to work well, he said.

Engineers who consult for TV stations said it’s hard to predict how digital signals will fare, especially because, unlike wireless cellular networks, broadcasters have much less control over viewer equipment. “Broadcasters, and even the federal government for that matter, really have limited control over what the viewer is getting on the receive end,” said President Bob du Treil of du Treil, Lundin & Rackley. “There are probably solutions to every problem, it’s probably going to take some time to work through it.” His firm has dealt with issues at both VHF and UHF stations, du Treil added. “So it’s not something that seems to be uniquely defined to any category of stations.”

President Don Everist of Cohen, Dippell and Everist agreed: “It’s very random and it’s very scattered and it’s very site-specific.” Because of the high number of variables, the average consumer doesn’t have the technical expertise to “make all of those distinctions” between various types of set-top boxes, for instance, Everist said. “As much as the old analog system was not well thought of, it had a component that is hard to replace, which was graceful degradation.”

Traditionally, TV stations have wanted VHF channels, because in the analog world people could receive them easier than UHF. But in digital, UHF works better, particularly for indoor antennas and in city cores, because shorter UHF wave lengths pass through windows and doors better, said Lynn Claudy, NAB senior vice president-science and technology.

“Like any new technology, a day of operation is worth a thousand pages of engineering analysis,” said President David Donovan of the Association for Maximum Service Television. “You have got to see how it operates in the real world, especially with RF.” Solutions for those who lost TV in the transition are going to have to be worked out on a case-by-case basis, he said.? There’s “no one-size-fits-all solution,” Claudy agreed.? The FCC is looking at power increases for some of the VHF stations, he said, and other stations are looking at switching back to UHF.? But all of the options involve interference “trade offs,” Claudy said.

Donovan, whose association is largely focused on preventing interference to TV spectrum, also sees another big lesson for the future.? Referring to efforts to allow un- licensed radio devices in the TV “white spaces,” he said the RF surprises in the transition show that “if you are going to put new devices in the RF spectrum, you have got to have real-world experience first.”