DTV: A Few Tweaks Left
Stations, FCC working to solve VHF reception snafus
Stations, FCC working to solve VHF reception snafus
WHDH Boston didn't expect to still be paying the electrical bills for two transmitters come late June 2009. Like many U.S. broadcasters, the Sunbeam Television station and NBC affiliate had already exceeded its original transmission budget when the government pushed back the turnoff date for analog signals from Feb. 17 to June 12. WHDH Engineering Director Jim Shultis looked forward to shutting down high-powered digital broadcasts on UHF Ch. 42 and launching digital signals on VHF Ch. 7, the station's former analog assignment.
But as of last week, WHDH was still running transmitters for both Ch. 42 and Ch. 7. And both were being used to deliver the station's digital TV signal, which many Boston viewers couldn't find on its new Ch. 7 home after WHDH made the switch on June 12 and began broadcasting at 29.7 kilowatts.
After receiving numerous viewer complaints, WHDH petitioned the FCC late on the afternoon of June 15 for an STA (special temporary authority) to resume DTV broadcasts on Ch. 42, and was back broadcasting a simulcast of its Ch.7 there at 1:12 pm on June 16. The FCC says the station can continue broadcasting on Ch. 42 until the reception issues on Ch. 7 are resolved, as long as that doesn't cause interference to other stations.
“We've received immense viewer feedback,” says Shultis of the relaunch of Ch. 42. “'Thank you for bringing it back,' that type of deal.”
WHDH is one of several big-market outlets, including ABC-owned stations in Philadelphia and Chicago, to experience significant problems with reception since switching to a VHF channel for their permanent DTV operations. According to viewer comments and interviews with engineers, many of these stations were received reliably on their former UHF assignments but are now hard for viewers to find, even for those with an adequate UHF/VHF antenna. On the other hand, there have been few complaints of significant reception problems from stations with high-powered UHF assignments.
The FCC has moved quickly to address the issue. Besides granting the STA to WHDH in less than 24 hours, it has also helped out another Sunbeam station, WSVN Orlando, and Schurz-owned KWCH Wichita by granting them power increases. It has also redeployed forces to Philadelphia and Chicago to help tackle reception problems there, and is discussing solutions including boosting power or installing a translator to fill in coverage to affected areas. By the end of last week, the FCC was scheduled to place engineers in Baltimore; Nashville; Raleigh, N.C.; Rochester, N.Y.; Orlando; and Richmond, Va., to help stations who have asked it for assistance, either with DTV consumer outreach or technical issues with signal reception.
Some of the problems with VHF reception are simply due to consumers not having the correct antenna; many antennas marketed as “HDTV-ready” are UHF-only. And the double-rescan procedure recommended last week by the FCC has solved the issue for some viewers in New York and Chicago. But in many cases, the reception problems are more severe in close proximity to the transmitter than farther away. That suggests the problem is less one of signal coverage than of signal penetration into urban dwellings such as apartment buildings, where many viewers rely on simple indoor antennas.
“Most of the viewer complaints have been within 10 to 12 miles [of the transmitter],” says WHDH's Shultis. “It's like we have distance—the people out 20 to 30 miles with outdoor antennas are getting us—but we have poor penetration. On Ch. 42 at 948 kW, which is just under a megawatt, we had so much better penetration. ”
Caroline Welch, program director for WPVI Philadelphia, says reception of her station's 7.5-kW signal on Ch. 6 has been random, with next-door neighbors and houses on opposite sides of the street experiencing completely different reception. But many of the problems for Ch. 6, which also suffers interference from FM radio stations, have been close to the transmitter site in the Roxborough section of Philadelphia.
“There is no definitive spot, which is part of what makes it a little more of a complex issue,” Welch says. “You can't just say, if you live here, you can't get it.”
Engineers say the fact that VHF DTV signals don't seem to be having as many problems on the West Coast is due to the different construction techniques used there compared to cities farther east like Chicago and Philadelphia.
“One of the things we've found is that with the same Ch. 7 in Los Angeles and San Francisco, there's not as much of an issue,” says WLS Chicago Engineering Director Kal Hassan. “You've got stucco construction out West, and the VHF penetrates well. But in the East you have a lot of brick construction and aluminum siding, and all of that is harder.”
WLS, which has also experienced DTV reception problems from viewers living close to its transmitter atop the Sears Tower, never had reception problems with Ch. 7 in analog, Hassan says. But while it used to broadcast analog VHF at 55 kW, it is only allowed by the FCC to transmit digital VHF at 4.75 kW to avoid interference with stations in Milwaukee and Grand Rapids, Mich.
However, simply boosting the power may not be a quick fix in every market. Engineers note that some consumers with amplified antennas have actually been getting too much power and are overloading their receivers, rendering them useless to tune any channel. Installing signal pads between the antenna and receiver, which dampen the power sent to the receiver, have solved reception issues in some cases.
“We don't want to rush to judgment,” says FCC spokesman Rick Kaplan. “What we're finding are problems with limited stations and limited markets, and each problem appears to be different. That's why we're going to stations when they've asked us to, to try to find out what the problems are.”
—John Eggerton contributed to this story
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