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Avi Beacon Top Tips for Preventing Electromagnetic Interference

Certain electronic devices and other objects can interfere with an avalanche beacon's ability to send and receive signals — the UIAA just released a list of tips for mitigating that risk.

skier holding up pieps dsp pro transceiver with two other skiers in background(Photo/PIEPS)
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Electronic devices like phones and cameras emit electromagnetic signals that can disrupt avalanche transceivers. And in an emergency, when time and accuracy are essential, electromagnetic interference (EMI) is working against you. It could make the difference between rescuing someone and recovering them.

The International Climbing and Mountaineering Federation (UIAA) recently released an updated position statement statement regarding EMI in avalanche transceivers. It comes on the heels of a comprehensive consultation process the UIAA completed. It incorporated presentations from organizations, federations, and leading experts and looked at insights and feedback from all avalanche transceiver manufacturers.

The UIAA describes the evidence it considered as both “overwhelming and compelling” that EMI is a critical issue. And it offers some helpful, constructive — possibly lifesaving — recommendations for mitigating it in the field.

What Is Electromagnetic Interference?

Mammut Barryvox S avalanche tranceiver
A modern, cutting-edge avalanche transceiver from Mammut; (photo/Seiji Ishii)

When a device’s electrical path, circuit, or signal is disrupted by an outside source, it can tamper with a device’s ability to function.

If you place a cellphone next to a speaker, you can sometimes hear noises or beeping. That’s an example of EMI. The phone’s signal is actively interfering with that of the audio equipment. The same thing is commonly called “feedback” when EMI affects a guitar and its amplifier.

But EMI doesn’t have to come from an active, functioning electronic device. In sensitive devices, it can also be caused passively. Simple metal parts, metal cases, foils, magnets, and wire mesh are enough to sometimes cause it.

In the case of avalanche beacons, this curious scientific phenomenon becomes a matter of life and death. If something is disrupting a beacon’s “Send” (or “transmit”) signal, it will confuse other beacons that are in “Search mode” (or “receiving” a signal). That could provide misleading distance and direction indications. It could even provide false positives, leading rescuers to the wrong location.

UIAA identifies phones, video cameras, heated apparel or gear, vehicles, and walkie-talkies as active sources of EMI. It even includes battery-operated avalanche packs (like the Litric or Alpride systems) in its list of potential sources of EMI.

Realistically, skiers aren’t going to start leaving all that gear at home. So, what can people do to mitigate EMI even when you’re carrying those electronics on you?

UIAA Tips for Preventing EMI in Avalanche Beacons

UIAA releases statement on mitigating electromagnetic interference (EMI) in avalanche beacons

For starters, UIAA recommends keeping any potential EMI disruptor — passive or active — at least 20 cm from your beacon. So, if your beacon is in its cradle on your chest, you should keep your cellphone, car keys, wallet, and other potential disruptors in the opposite pants pocket. It also warns against wearing action cameras at chest level if the beacon is cradled.

Essentially, UIAA recommends keeping anything that could be a potential source of EMI as far from your beacon as you can keep them.

From there, the UIAA breaks its advice for mitigating EMI into two parts: Mitigating EMI for beacons in Send mode and mitigating EMI for beacons in Search mode.

Mitigating EMI in ‘Send’ Mode

The recommendations for beacons transmitting a signal are simple: “All devices may remain in use.”

That means, while you’re skiing or touring, you can leave your phone, camera, heated socks and gloves, and battery-operated avi packs powered up. As long as they’re 20 cm away from the beacon, the transmitting signal will be strong enough for other beacons to pick up.

The logic here is simple. People aren’t realistically going to turn every electronic device off at the top of every run and turn them all back on at the bottom. And if someone is buried, they can’t be expected to turn things off under the snow.

Mitigating EMI in ‘Search’ Mode

The recommendations for beacons in search mode require more action. The UIAA recommends that all electronic devices be immediately turned off or ditched as soon as someone is buried.

Cellphones, walkie-talkies, and other communication devices should be turned off (as in, shut down, not placed in airplane mode). All heated gloves, socks, liners, and boots should be turned off. Drop your battery-operated avalanche airbag a safe distance away. And if you’re wearing an electronic or magnetic watch, hold your searching beacon in the opposite hand.

While searching, active EMI sources — like phones, radios, or Satcom devices that haven’t been turned off — must be 10 m from the search beacon to maintain an accurate signal. UIAA also notes that you should be 10 m away from any snowmobile or other vehicle if its engine is on.

Keys, wallets, and other passive sources of EMI must be kept at least 50 cm from the beacon to maintain an accurate signal.

If you think turning off your equipment will take too much time, hand it off to someone who is not actively searching or set it all aside.

Identifying False Positives

(Photo/Nate Mitka)

If EMI interferes with a beacon signal, it can generate “false positives,” confusing searchers. They might think they’ve located a buried individual and start digging, only to realize that they’re in the wrong place.

The UIAA notes that if your avalanche beacon gives off an analog sound approximately every second with distance and direction indications, it’s likely an authentic signal of a buried subject.

However, if that signal makes no analog sounds or does so infrequently, it’s a sign that the beacon is affected by EMI. That’s even if it’s still providing distance indications. If a rescuer notices that their beacon isn’t making consistent noises, EMI could affect their search.

Stay Prepared: Prevent Electromagnetic Interference

(Photo/MTN Guide)

The UIAA is an organization dedicated to ensuring the welfare and safety of mountaineers worldwide. This position statement and the associated recommendations on transceiver EMI are part of its effort to compile a repository of published documents on this issue and its risks. The hope is to eventually propose a baseline standardization for avalanche transceivers worldwide. You can download a PDF of the UIAA’s position statement on EMI in avalanche transceivers here.

The UIAA concludes its statement by noting that further research is warranted on the topic of electromagnetic interference and avalanche beacons. It recommends that people stay up-to-date on current research and their own electronic safety equipment.

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