When residents of a Philadelphia suburb complained to an area television station about how their remote car door entry devices wouldn't work in the parking lot of a local department store, an investigative reporter for NBC-10 (WCAU) called everyone she could to help her discover why. No one knew anything -- until she called on some local ham radio operators.

"Many people lock and unlock a car by remote and don't even give it a second thought unless it doesn't work," said NBC10 reporter Lu Ann Cahn. "The mystery problem repeatedly occurs outside the Kohl's store in Royersford. When I went into Kohl's [to ask about this], they told me they had no idea [about this]."

Cahn said that shoppers told her that this has been going on for more than a year, and that some shoppers don't realize they might have to manually lock their doors: "One woman reported her laptop was stolen from her car after she thought she had locked it."

Shoppers theorized that it was the local power plant causing the interference, but Cahn said that officials at the plant said it wasn't them. Others thought that cellular telephone towers might be the culprit, but there are no cell towers in the area. "Police tell us that they can't figure it out either," Cahn said.

So after calling numerous places to help her out with this mystery, Cahn happened upon Reggie Leister, N3KAS, and Bob Rex, K3DBD, of the Pottstown Area Amateur Radio Club (PAARC); Rex is Vice President of the club and Leister is the club's Public Information Officer (PIO). And as hams do, they were quick to volunteer to help out.

Leister and Rex accompanied Cahn to the parking lot in question. Rex built an antenna out of aluminum tubing and hooked it up to a spectrum analyzer. "Somewhere in the vicinity of this parking lot," Leister said, "there is a big source of radiation, some sort of signal." When Leister aimed the antenna in the direction of the Kohl's store, he hit pay dirt. "There are actually two signals there. It looks like [they're] coming from the building," Rex said when he read the analyzer.

Leister and Rex moved in closer to the building and pinpointed that one signal was coming from one set of doors, while the other signal emitted from another set of doors. Rex, an engineer, said that the thing that bothers him about this is that the signals "are running constantly." When Cahn approached Kohl's management with their findings, she was told that "they will look into it."

"The FCC licenses radio signals and these ham radio operators say the fact that some signal is interfering with remote locks isn't good," Cahn said in her report. Rex concurred, saying, "The FCC rules are pretty clear on that. It might be something that's broken." Leister and Rex agreed that the store security sensors located at each set of doors might be the culprit.

Three days after Leister and Rex located the source of the interference, remote car door lockers worked again. "Kohl's will only say that they're working on it," Cahn said. "The FCC says it does sound like something malfunctioned and they have had reports of similar incidents in New York City and Tampa, Florida."

A few days after they found the signals, Leister explained that he and Rex did not think the anti-shoplifting detectors were the problem: "What we are guessing here is that they are probably connected to some kind of device that triggers a security camera to come on if there is a breach. Except instead of just sending out a quick 2-5 second (Part 15) blip, these seem to be on continuously and exceeding the permissible signal levels."

Cahn was quick to give credit to the local hams who stepped up to the plate and helped crack this mystery: "We here at NBC10 were so curious as to why these remote car locks would just stop working, so we thought we should really try to solve this mystery. I have to give kudos to Reggie Leister and Bob Rex with the Pottstown Area Amateur Radio Club. They were so great and so excited. You don't know how many people we called -- police, Triple A, car dealerships -- we called so many people trying to figure this out and nobody knew anything until we talked to these ham radio operators. They were so wonderful and they knew all about radio signals. They created their own gadgets to help us figure this out. We really want to thank them for their help with this."