Hams Help Trace “Mystery” Signal Disrupting Keyless Entry Devices in Ohio
From ARRL de WD1CKS@WLARB to QST on Tuesday, May 07, 2019 20:04:34
A recent article in The New York Times reported that many garage door openers and keyless vehicle entry fobs in an Ohio town near Cleveland mysteriously stopped working. While the article invoked The X-Files and hinted initially that a NASA research center somehow could be involved, the cause was not so much mystifying as arcane.
"Garage door repair people, local ham radio enthusiasts, and other volunteer investigators descended on the neighborhood with various meters," the May 4 article by Heather Murphy recounted. "Everyone agreed that something powerful was interfering with the radio frequency that many fobs rely on, but no one could identify the source."
More than a dozen residents reported intermittent issues getting their key fobs and garage door openers to operate, and most lived within a few blocks of each other. At one point, the local power utility started shutting off power to areas where the strongest RF signal was detected, but the signal persisted. Dan Dalessandro, WB8ZQH, a TV repairer, was among several hams who investigated. He initially picked up "little blips" on a signal detector, but finally, on one block and at a particular house, the signal was quite loud.
"The source of the problem was a homebrew, battery-operated device designed by a local resident to alert him if someone was upstairs when he was working in his basement," the Times reported. "It did so by turning off a light." The individual, who, the article said, has special needs, was not identified for privacy concerns. The inventor, who had no malicious intent, had no inkling that his device was wreaking havoc on the neighborhood until a North Olmstead City Council member and a volunteer knocked on his door. The device operated on 315 MHz, the frequency many keyless-entry devices use under FCC Part 15 rules. The device's battery was removed, the signal stopped, and all who were involved breathed sighs of relief.