DTV Notes
KUAC Makes Unusual Digital Switch
Alaska station goes from UHF to VHF
By Glen Dickson --
Broadcasting & Cable, 11/2/2009 2:00:00 AM
After full-power broadcasters ceased analog operations on June 12 and settled into their final digital TV (DTV) assignments, one of the early findings was that stations with VHF channel assignments were experiencing far more reception problems than their UHF counterparts.
Reception issues were particularly prevalent in Eastern cities like Philadelphia and New York, where the number of stations in close proximity meant that VHF stations had to curtail their power to avoid interference and were often left with signals unable to penetrate into apartment buildings for reception on small indoor antennas.
The FCC has since granted power increases to a number of VHF stations, and let others switch their digital assignments to available slots in the UHF band. Raycom Media, for example, has switched WLOX, its Biloxi, Miss. station, from VHF to UHF operation, and plans to do the same at its Jackson, Miss., station, WLBT, next month. And WCPO Cincinnati wants to move from its current VHF Ch. 10 assignment to UHF Ch. 22, even though the Scripps Television station has already received a power increase.
“We're still finding areas where the digital signal is not acceptable and is not being received at all,” says Mike Doback, VP of engineering for Scripps.
But at least one station, KUAC Fairbanks, Alaska, decided to move in the other direction to solve its reception problems. The public broadcaster actually switched in late September from a DTV assignment on UHF Ch. 24 to VHF Ch. 9, its previous analog home, undergoing a “rechannelization” process that required it to go off-air for six days.
Using funds from a Corporation for Public Broadcasting grant, KUAC spent $1.1 million on a new Harris VHF transmitter and ERI transmission line and antenna, which were installed in a tightly coordinated process designed to take advantage of Alaska's brief window for weather conducive to tower work.
The Fairbanks market never had a UHF station until stations began broadcasting DTV. So when KUAC began broadcasting DTV on Ch. 24 in 2004, it didn't expect many viewers to have the proper UHF antenna required to receive the signal. The station also had a relatively low-power allocation for UHF of 79 kilowatts ERP (effective radiated power), and actually went on-air at a licensed power of 69 kW. Initial tests showed reception problems at a range of only 11 miles from the transmitter.
But with roughly 28% of the market relying on over-the-air service instead of pay-TV, plenty of homes were already equipped with roof-mounted VHF antennas, particularly those residing in the “bush” communities on the fringes of the market. Fairbanks also doesn't have a lot of big apartment buildings with viewers relying on indoor antennas. More important, the power costs of running a higher-powered UHF transmitter weren't feasible for a public broadcaster like KUAC.
So the station filed a request with the FCC several years ago to switch its DTV assignment to its old analog position at Ch. 9. While that request was granted, it was only at an effective radiated power of 3.2 kW, which KUAC feared would still result in coverage issues. So it subsequently asked the FCC to maximize its power to 30 kW.
That request was granted in late March, but due to budget issues, scheduling with vendors and tower crews, and Alaska's harsh spring weather, KUAC wasn't able to launch DTV on Ch. 9 on June 12. The complaints from viewers forced to rely on Ch. 24 for service flooded in, as homes in the outer ranges of the Fairbanks market were unable to receive the DTV signal.
“We had hundreds of calls,” says KUAC Director of Engineering Keith Martin. “We knew it was going to happen, but there was nothing we could do about it. We had everything in the works to fix it, but the timing was pushed out to September.”
So KUAC worked with Harris, its prime contractor on the project, to get the work done before the long Alaskan winter set in and with minimum interruption to on-air operations. Besides installing a new transmitter, antenna and transmission line, the tower's foundation had to be reinforced, and new guy wires and guy piers installed. The bulk of the work was done in a week, between Sept. 13 and 20, and the station was off-air from Sept. 14 to 20. Luckily, the weather cooperated.
“The week we had was in the 50s, so it was perfect,” says Nathan Smith, program manager of transmission for Harris.
KUAC did heavy community outreach to alert viewers, including ads in local newspapers and e-mail blasts, and a follow-up round reminding them to rescan their converter boxes or digital TVs to find the station on Ch. 9. Although KUAC had planned to be off-air until Sept. 23, it resumed operations part-time three days earlier, and soon started receiving phone calls from happy viewers.
As Martin puts it: “The impact wasimmediate.”
KUAC’s UHF-to-VHF success story is certainly unusual, says John Howell, manager of installations for Harris. The company is currently working with about 150 stations to improve their DTV coverage, says Howell, but most of them are looking to maximize their power, including several VHF stations in the Plains states. Those stations looking to switch assignments are “predominantly going from VHF to UHF,” says Howell.
According to the FCC, of the 79 full power television stations requesting a channel substitution, 22 stations asked to change their channel allotments from a VHF to a UHF channel. Less than 10 went from UHF to VHF.
The problems suffered by high-V stations like WCPO Cincinnati are somewhat ironic, says Scripps’ Doback, as several years ago stations with a high-V assignment thought they would “be in heaven” because of the expected combination of good signal propagation and low power costs.
“It’s only now that we’ve found out the planning factors were probably wrong in terms of how much power you need to replicate analog service,” says Doback.
Raycom’s VHF reception problems in Biloxi and Jackson were primarily due to adjacent-market, co-channel interference issues that prevented the stations from broadcasting at a high enough power to replicate analog coverage, says Chief Technology Officer Dave Folsom.
“It’s not an indictment of VHF,” says Folsom. “There’s nothing inherently wrong with VHF. It’s just easier to have interference, because it goes out further.”
http://www.broadcastingcable.com/art...tal_Switch.php 
