By JASON LAUGHLIN
Courier-Post Staff
LINDENWOLD

A Boston-area TV station's new 24-hour-a-day digital signal is disrupting Camden County's police communications system, threatening public safety by drowning out calls from officers to central dispatch in certain kinds of weather.

Camden County, whose system operates on the same frequencies as the TV station's, has appealed to the Federal Communications Commission for help, but so far no solution has been found.

It has been joined by Ocean County, where the problem is even worse, and Burlington County. Burlington County fears it could face similar disruptions in the future because it also now shares some of the same frequencies as the two other counties and the TV station.

The problem has the potential to leave an officer in the middle of a dangerous situation with no way to call for backup or ask for help.

"Losing communications even for the shortest of times could be dangerous for the public and our officers," said Chris Ferrari, police chief of Oaklyn, one of 31 Camden County communities served by the central communications center.

Rep. Rob Andrews, D-N.J., has met with county representatives over the issue and is working to arrange a meeting between county personnel and FCC officials in Washington.

"This is a very big deal," he said. "I want to call this to the attention of the most authoritative person at the FCC we can find."

Twice this summer, the signal of WCVB in Needham, Mass., interfered with communications from the field to Camden County's communications headquarters in Lindenwold, said Rick Connor, the county's technical services director.

Normally, the station's signal travels only about 50 miles. But under certain atmospheric conditions, it can go hundreds of miles.

The most serious disruption occurred during the middle of the night on June 9 when the TV signal drowned out calls from hand-held radios and some car-mounted units over the course of two hours, Connor said. Lawnside officers were the first to report the problem.

"In this business, one time with one cop with one syllable that can't get through, that is unacceptable," Connor said.

All but Camden, Cherry Hill, Voorhees, Pennsauken, Gloucester Township and Winslow are on the county system. They have their own communication systems, which use different frequencies. Fire and ambulance communications in the county also operate on different frequencies, so they are not subject to interference.

The TV station's signal has not been strong enough to disrupt 9-1-1 dispatches from Lindenwold, and officials said the incident in June and a much briefer one in August did not result in any harm to public safety.

The problem could turn up in Burlington County because the county recently bought several frequencies on the same bandwidth as the TV station, said Joseph Saiia, Burlington County public safety director. Gloucester County also uses similar frequencies but has not experienced any problems, its communications director said.

WCVB began broadcasting a digital signal on Channel 20, 506 through 512 megahertz, in 1998. But the problem did not show up in South Jersey until this year because the station began round-the-clock digital programming only in January.

The communications logjam has been blamed on a weather condition known as tropospheric ducting, which usually occurs on summer nights. Layers of warm and cool air create a kind of "duct" that traps radio transmissions, allowing them to travel hundreds of miles without breaking up - in this case about 270 miles, Connor said.

Interference is even worse in Ocean County because of its proximity to the ocean, which helps create the conditions that result in transmissions traveling longer than normal distances.

Mike Keller, chief engineer at the TV station, said the problem should have been anticipated.

"I think what happened here is somebody underestimated," Keller said. "There's nothing new here. Skip and bouncing of signals has been going on forever."

Keller was alerted to the problem by Ocean County. He said WCVB is willing to work with local communications centers. But he said the station is operating within the parameters of its license and there's not much it can do.

Camden and Ocean counties blame the FCC for not having planned better in its efforts to transfer all TV stations from analog to digital broadcasts. The FCC should have known atmospheric conditions could cause a station signal in Boston to travel this far south, county officials said.

To solve the problem, either WCVB or Camden County will have to get new signals, Connor said. There are no other frequencies available that could handle the county's growing needs for police communications, he said. Shortening the Camden County antennas might help the problem, but it would require the county to nearly quadruple the number of repeaters, or relay towers, used to pass a signal along, Connor said.

"Public safety has first priority on the bandwidth," Andrews said Thursday. "I think the FCC had an obligation to assess the impact of giving that frequency to the Boston station and they failed to do that."

An FCC spokeswoman did not know enough about the problem to discuss the agency's decision-making, but said the FCC expected the move to digital stations wouldn't be a painless one.

"We expected some wrinkles and we will look at each one and work to resolve any problems," she said.

Camden County has developed a short-term backup plan, but officials said they could not discuss it for security reasons.

Repeaters dispersed throughout the county are intended to exchange messages among mobile and portable units and the central dispatch office in Lindenwold. During periods of interference they pick up the TV signal instead, translating it into noise the receivers can't translate.

A standard analog TV transmission is made up of peaks and valleys of energy, so even when it interferes with local frequencies, one frequency is more affected than the other. But digital transmissions fill the entire set of frequencies on a channel equally. Weaker transmission sources, like from a portable radio, are drowned out across the channel.

The FCC has mandated all TV stations switch to digital transmissions, which are viewed as a more efficient way to use the spectrum.

Reach Jason Laughlin at (856) 486-2476 or jlaughlin@courierpostonline.com