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I have been told that electronics can possibly interfere with avalanche beacons (cell phones, radios, etc., but even flashlights). Is there any truth to this? A source would be helpful, ideally from a beacon manufacturer themselves.

If this is indeed the case, how large is the impact: would it slow down a search, make it impossible, or not measurably change anything?

What can one do to protect themselves from interference by electronics?

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Yes it does, especially mobile phones.

I attended an avalanche course last year. The guide did a very simple demonstration. He powered his avalanche beacon on "send" mode, and put it on his backpack over the snow surface. All participants walked away from his beacon in a straight line with their own beacons in "search" mode. We all marked in the snow the distance where our own beacon stopped receiving the signal (not all devices have the same search range).

The guide then repeated the exercise with his mobile phone placed 20cm from his beacon. The phone was switched on, he had 3 out of 4 bars of signal (with 4G), and did not make/receive any call or SMS during the test. We again walked away from the beacon in a straight line: Every participant stopped receiving the signal about 10-12m earlier than for the first test.

In conclusion: If you keep your mobile phone in your pockets and you are buried under the snow in an avalanche, the range at which the signal of your device can be detected by other people is significantly reduced! As result, it takes more time to find you, and the risk of death increases.

I personally keep my mobile phone in airplane mode: first it saves battery for an emergency, secondly it reduce the interfere with the avalanche beacon. Third (this is personal): it is OK and feels good from time to time ;-)

As for references:

Avoid having other electronic devices (e.g. mobile phones, radios, headlamps, cameras), metal objects (pocket knives, magnetic buttons), or other transceivers close to your running avalanche transceiver.

Mammut Barryvox manual

How strong is the disturbing influence of my cellphone?

Cellphones, especially smartphones, as well as other electronic devices (e.g. cameras), can influence the functionality of your avalanche transceiver in the close range. This applies for all avalanche transceivers!

Possible effects on send function:

Reduction in signal strength and therefore range reduction for faulty transmitter.

Possible effects on search function:

• Reduction of receiving range
• Wrong direction and/or distance indication
• Display of additional, non-existent transmitter

For all electronic devices, as well as metals and magnets, a minimum distance should be observed: 20 cm in SEND mode, 50 cm in SEARCH mode.

Pieps Transceiver Knowledge

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    On the other hand, if your incandescent flashlight is interfering with an avalanche beacon, something is badly wrong with either the flashlight or the beacon. – Mark Jan 25 '18 at 23:50
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    You haven't said how far the range was without the cellphone on. Losing 10m from a 500m range is probably not a big deal, loosing 10m from an 11m range is basically non functional – Richard Tingle Jan 26 '18 at 8:18
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    We walked between 60 and 80m (the sending device was over the snow surface, under the snow, the distance would be much shorter), depending on the device of the participants. – Giomsen Jan 26 '18 at 8:38
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    The statement "It is wise to keep your mobile phone in airplane mode" is not supported by the experiment nor the sources. The testing you conducted did not include phone in airplane mode, nor do either of the sources suggest it. The testing and reference do not allow for a phone to powered on at all near the avalanche beacon. – James Jenkins Jan 26 '18 at 13:25
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    I'm surprised at this. I would like to see some other tests. A: Repeat the test with the phone in airplane mode. B: Repeat the test with the phone off. C: Repeat the test with one of the searchers carrying the live phone. D: Repeat the test with one of the searches carrying the airplane mode phone. – Sherwood Botsford Jan 27 '18 at 22:03
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I am the lead hardware engineer for Backcountry Access.

Interference from personal electronic devices (PED) is very real, and it can range anywhere from minimal impact to severe. The reasons are a little complicated to understand, but basically the worst case is if the PED emits a signal at or very close to 457kHz, which is the beacon frequency.

LED headlamps could have an internal regulator or dimmer emitting large signals in this band unintentionally. The dimming circuitry can actually make the problem much worse! If you absolutely must have an LED light near the searching beacon, the best thing you can do is to switch it to full brightness, so that the dimming circuitry is less likely to cause problems.

Beacon designers do everything possible to minimize this problem, but we have no control over other electronic devices.

Cell phones and other devices don't intentionally transmit here but they emit broadband noise and other signals which makes it more difficult to hear weak beacon signals. Two way radios, MP3 players, even something like a digital watch or heart rate monitor could emit a signal that interferes. (REALLY!)

"Airplane mode" turns off the radios in the phone, but those are the LEAST of the problem! The processor itself, display, and much other internal circuitry is still on, and can still emit enough signal to mask a beacon unless you are very close.

The nature of the interference will change with different operating modes (play vs standby etc) and as the battery level changes, or at different temperatures, so a device that doesn't seem to cause a problem today can be worse or severe tomorrow.

The best thing you can do is to turn those devices OFF when searching. The second best is to get those devices away from the search area. In general doubling the distance from the PED to the beacon receiver will cut the interference by 4x.

An old analog beacon like the Ortovox F1 can be used to illustrate the problem because it allows you to hear what the beacon electronics are trying to deal with. You might find it interesting to grab one cheap on Ebay and have a listen.

From a practical standpoint, the biggest threat is electronics carried by the searchers which can create signals that interfere with the ability of the receivers to hear weak beacon signals at larger distances. Electronic noise emitted by PEDs carried by the victim are not an issue.

In the lab, I can place my cell phone a few inches away from a transmitting beacon. When the beacon is off, my cell phone noise is detectable at about 1.5 meters. Some phones are worse, some are better. With the beacon transmitting, the cell phone noise is completely undetectable during the beacon transmissions. In between beacon pulses, the cell phone again becomes detectable. From a few meters away our to full range, the cell phone will be undetectable while the beacon transmitter will be clear. Get that Ortovox and have a listen!

It is conceivable that PEDs on the victim could, at very short range, confuse the searcher by showing up as a second weak signal.

Metals VERY close to the transmitter (inches) can cause an increase in power consumption in transmit mode, and can distort the field which might cause errors in pinpointing.

When we get into what "could" happen, it can get confusing, and I don't want to risk creating any more myths about how beacons work, but I do want to answer completely and honestly.

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    Welcome to outdoors.sx and thanks for a great answer! To clarify, do the electronics interfere only with the search mode or both search & send? – Felix Mar 15 '18 at 15:25
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    From a consumer point of view, the most significant issue is when the interferer is near the searcher. The interferer can deafen the reciever, or create false pulses, or both. – David VanHorn May 11 '18 at 17:47

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