Avalanche Transceivers - Electromagnetic Interference

Mark Staples
Director, Forest Service Utah Avalanche Center
Avalanche transceivers are susceptible to interference by electronic devices, metal objects, and magnets if they are too close. Every day there are more electronic devices being carried into the backcountry. Of particular concern may be heated clothing.
The guidance below provides practical guidance on how to avoid problems with interference. It was created through a collaboration by Avalanche Canada, the US National Avalanche Center, Colorado Avalanche Information Center, Utah Avalanche Center, Northwest Avalanche Center and the six avalanche transceiver manufacturers: Arva, BCA, Black Diamond, Mammut, Orthovox and Pieps. Thanks to Avalanche Canda for creating the images below!
There are two scenarios in which interference may occur:
  1. Interference with a transmitting transceiver (send mode). This must be addressed and dealt with before going into the backcountry. If you are buried and wearing something causing interference, you will not be able to fix the situation.
  2. Interference with a receiving transceiver (search mode). This one should also be addressed and fixed before going into the backcountry; however, if a searcher can recognize interference is happening during a search, they would have an opportunity to deal with it as long as they can accurately recognize the interference.
Interference with transceivers generally presents as either reduced range or ghost signals. 
The GOOD NEWS is that interference has a simple solution - DISTANCE. Add distance between the transceiver and the object creating interference. The guidance below will help you understand how much distance you need. 
The 20/50 rule is that you want your beacon 20cm (8") away from other electronics while transmitting and 50cm (20") away from electronics while searching. 
Leave a comment
Wow! Great info. This material is being asked about, and talked about more and more as technology and clothing combine. Next, heated jackets.
Michael Davis
Tue, 2/7/2023
It had not occurred to me to take off my bluetooth connected GPS watch. I seem to remember old transceivers being mounted on the center of your chest. Now the tend to be lower left abdomen. 20cm away from a pacemaker. Thanks for the information
Pete Freeman
Sun, 2/19/2023
Great information, if you have a link to more detail about how the interference was tested I'd be curious. I did my own backyard tests a couple of years ago using a Mammut Barryvox S and a Mammut Element beacon. As expected, I saw major interference in search mode from an iPhone, seemingly about equal in magnitude between regular and airplane mode. Interestingly, I didn't see any difference in search mode when I held a transmitting radio right next to the beacon. I used both a BCA transmitting at 2W and a Baofeng at 5W. I had similar results when the electronics were next to the sending beacon. I found that quickly moving my phone to my back pocket created enough distance and the increased shielding from my body probably helped too. A friend and I have hypothesized that a clothing manufacturer could incorporate a Faraday pouch pocket into a touring pant that could eliminate any phone interference.
Thu, 3/9/2023
Hello Steve, Here is a link to ICAR on some beacon work they did in 2022. Thanks for your information on your backyard tests. The big problem that operations have been have is with the draw of power to operate the screen. This is something that has come up in other tests. Moving your phone to your back pocket increases the distance and is probably suitable for what you're doing. There has been some work that has been done on pouches- but no testing that we're aware of. Thanks,
Fri, 3/10/2023