Avalanche transceivers work by transmitting and receiving high-frequency sound waves. Electrical interference can occur when electronic devices—like cellphones, radios or even head lamps—disrupt these sound waves by emitting high-frequency noise themselves. The result of electrical interference can include a delayed rescue—or worse.
Fascinated by frequency
Steve Achelis, a ski patroller and former commander of the Salt Lake County sherrif’s search and rescue team, recovered nine avalanche victims during his career.
“That’s where my interest in avalanche beacons originates,” said Achelis. Achelis, who is also a software engineer, conducted extensive tests on a wide array of avalanche transceivers.
“One of the more esoteric tests I did was I took more than 50 avalanche transceivers and used a $20,000 oscilloscope to measure what frequency they were transmitting at,” said Achelis, “and then I chilled them all down to five degrees Fahrenheit. Then I re-tested their frequencies to see both how accurately transceivers transmitted a signal as well as to compare by brand.”
Most units stayed within the allowable variance, but some older analog types had drifting frequencies that were worsened by the temperature drop.
Achelis’s interest in beacon testing has seen him running new tests every year on his growing collection of transceivers.
Important factors
Achelis said that aside from having signals blocked by a large metal object near by, transmitting units aren’t overly affected by electrical interference.
“What is affected is the receiving beacon, because it is listening very closely for this specific frequency of 457 kilohertz,” said Achelis. “If it is a strong signal close to the receiving beacon, it can confuse the receiving beacon.”
Achelis has observed this kind of distortion caused by two-way radios, MP3 players—even radios used by ski patrollers and search and rescue.
The solution to this potential problem is to keep the transceiver at least 30 centimetres away from potential sources of interference. While it might not be practical to turn off your phone or radio, even a small amount of distance between the devices can help transceiver reception.
