The ARRL have successfully helped Police in Evanston, Illinois to pin down the source of strange RF interference to vehicle car fobs signals and cell phones
The Police Department contacted the ARRL Lab, after an apparent interference source began plaguing wireless vehicle key fobs, cell phones, and other wireless electronics. Key fob owners found they could not open or start their vehicles remotely until their vehicles were towed at least a block away, nor were they able to call for help on their cell phones when problems occurred.
The police turned to ARRL after an unsuccessful approach to the FCC. The FCC considered key fob malfunctions a problem for vehicle manufacturers, although the interference was affecting not just key fobs but cell phones, which are a licensed radio service.
Evanston authorities worried that a serious situation could develop if someone were unable to call the emergency services, putting public safety at risk. They also were concerned that the RFI could be intentional and indicate some nefarious or illegal activity. Given the seriousness of this situation, Gruber contacted Central Division Director Kermit Carlson, W9XA, to ask if he could look into the matter.
Carlson employed a Radar Engineers 240A Noise Signature Receiver and UHF Yagi antenna to survey the affected block. Since key fobs typically operate at around 315 MHz and 433 MHz, he looked on both frequencies. The survey identified several noise sources in the affected block, but in particular a strong signal in the middle of the block. The interference source turned out to be a recently replaced neon sign switching-mode power supply, which was generating a substantial signal within the on-street parking area just across the sidewalk, between 8 and 40 feet from the sign.
Carlson called the Evanston case “a particularly alarming example of radio interference,” especially since local authorities considered it a public safety matter.