Do Phones Cause Avalanche Beacon Interference?

Do cell phones affect avalanche beacons?

Yes! Research has proven that electronic devices and magnetic materials can affect avalanche beacons (transceivers). Electronic devices like cell phones, GPS, GoPros and other cameras, radios, electric snowmobiles, and other electronic devices can interfere with beacons, ESPECIALLY when the beacon or transceiver is in SEARCH mode. 

Your avalanche beacon is one piece of equipment that you can flat out NOT afford to be dysfunctional when in the backcountry. 

So, let’s discuss the concept of electric noise and the effect is has on accuracy and overall performance of your avalanche beacon.

HOW IT WORKS

Avalanche beacons send out electromagnetic pulses (at 457 kHz) when they are transmitting. When you change your beacon to search mode, it receives the emitted pulses from other beacons and interprets the pulse via the internal antennae. With this information, your beacon determines the distance and direction of an emitting pulse (ie – your target or victim’s transmitting beacon).

However, the searching beacon will also pick up any frequency noise that happens at the same frequency as the transmitting beacon. This additional noise (ie electronic noise) is useless if it is not coming from your target, but anything in the 457kHz frequency is interpreted as a potential target.

If this excess noise is significant enough, it can cause false signals or inconsistent readings on your beacon. This is because if the miscellaneous electric noise is high enough, your transceiver can have a hard time deciphering the actual target signal from the unrelated items.

ACTIVE INTERFERENCE

Active interference means interference from electronic devices that are actively emitting radio frequency noise. Almost any running electrical item can be a potential source of electric noise. The most obvious and common is, of course, your cell phone. Cell phones can give off substantial amounts of electric noise, especially when running and even more so when the screen is on. Setting your phone to airplane mode has not been proven to decrease the amount of electric noise from your phone in any significant way.

Additional sources of active interference can be from GPS devices, radios, video cameras like GoPros, and really any other electric device or device with batteries. In general, its wise to assume that if you are carrying anything powered by electricity, there is a possibility of that item causing electrical noise

PASSIVE INTERFERENCE

Passive interference refers to when an item may block or distort transmissions, without necessary emitting anything itself.

Passive interference is usually only an issue when the item is very close to your avalanche beacon and can affect the performance of the internal antenna, usually by blocking the signal or altering the electromagnetic field around the device.

In most cases, passive interference would not significantly alter the ability to conduct a search. However, Backcountry Access and other avalanche resources recommend that users store any sources of passive interference 20cm (about 8 inches) from the beacon.

The most common type of source for passive interference are things that are metal or magnetic in nature. Things like your avalanche shovel, pocket knives, or aluminum foil come to mind and you should make sure these items are kept away from your beacon. Storing such items in your backpack is far enough to render any interference mute. 

BEST PRACTICES TO AVOID ELECTRICAL NOISE INTERFERENCE

It is generally understood that interference has a greater effect on transceivers in search mode rather than when it’s in transmit mode. For this reason, common practice is to keep any possible source of interference 20cm (about 8 inches) away from your beacon when in transmit mode and 50cm (about 20 inches, or 1.5 feet) when in search mode.

The longer distance is particularly important when actively searching, as you want to be absolutely sure you are getting the correct distance and direction to your target in an emergency situation.

The 50cm recommendation works out to being about arm’s length, therefore holding your beacon at arm’s length during search is considered proper technique and the way that you should practice using your beacon. 

For reference, follow these simple tips and guidelines to reduce the risk of interference with your avalanche beacon:

  1. Turn off electronic items that aren’t necessary and store them away from your beacon, in your pack
  2. Make sure electronics that are left on are at least 20 cm (8 inches) away from your beacon
  3. Keep metal items or foil away from your beacon
  4. Park snowmobiles and other equipment with spark plugs away from the search zone when beacons are in search mode
  5. For taking photos – take your camera or phone out only when needed to take the picture, then make sure to return it to a place away from your beacon.
  6. When searching with your avalanche beacon, hold the beacon out at arm’s length to limit interference and be able to keep your eyes up and aware of your surroundings
  7. If you think that there is interference with your beacon that you can not avoid and it may be impacting your beacons performance, reduce your search strip widths to 30 meters when performing a signal search

The amount of interference any given object gives off can vary quite a bit. Identical smartphones for example, can give off different levels of noise.

Some variation in interference can just be due to very small inconsistencies in manufacturing. Other variances may develop based on how worn your gear and equipment is.

General wearing down, cracks, or water damage can all affect potential interference which means that best practices for avoiding beacon interference aren’t absolute and you may need to adapt as necessary.

Final Thoughts

Hopefully this small bit of knowledge increased your awareness to potential issues with the interaction of common devices and your avalanche beacon.

You obviously should prioritize the functionality over all else in the backcountry. For additional resources and sources for some of the info provided in this post, see below:

https://www.mtavalanche.com/sites/default/files/Interference_Myth_NOT_Busted.pdf

https://www.mtavalanche.com/sites/default/files/Interference_Issues_Concerning_Ava_Rescue_Transceivers.pdf

https://backcountryaccess.com/en-us/blog/p/electronic-noise-and-what-it-means-for-your-beacon-2 

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