A hidden pirate radio antenna is the reason dozens of drivers in Hollywood, FL, couldn’t unlock or start their cars using keyless entry systems when parked near the local police station.
For months, drivers of certain model cars found their keyless remotes useless, only to have the problem disappear when the cars were towed to their dealerships for repairs. Some suspected electromagnetic interference from some sort of equipment at the police station, but local cops eventually fingered another culprit: a pirate FM radio transmitter hidden on the roof of a nearby bank building.
Once police removed the equipment — which was broadcasting Caribbean music — the problems stopped.
What makes this case interesting is that the pirate station was reportedly broadcasting at 104.7 MHz — well below the 315 MHz used by keyless devices for North American-made cars (European and Japanese cars use 433.92 MHz). If FM signals at 104.7 MHz normally jammed keyless entry, there would be chaos in parking garages all over the 107 U.S. cities with FCC licenses to broadcast full power at that frequency.
Most likely, the primitive pirate station blamed for the interference lacked filtering gear, and its 104.7 signal generated harmonic frequencies that interfered with the 315 MHz devices. If the outlaw broadcaster had spent a few extra bucks, his Caribbean beats might still be on the air, bothering no one but Hollywood residents trying to tune into the “hot adult contemporary” stylings of “Mix 104.7” WSGL in Naples, FL.
While this is the first reported case of pirate radio jamming keyless entry systems, the low-power devices are prone to interference from stronger signals broadcast on their frequency, which is within a range licensed primarily for use by the military and the federal government:
In a summary of radio spectrum use from the National Telecommunications and Information Administration, the frequencies in the range from 225 MHz to 328.6 MHz “are heavily used worldwide for critical military air traffic control and tactical training communications.” Specific functions include “air-ground-air communications for combat weapons training carried out at and in the vicinity of all major air bases and military training areas worldwide.”