Digital Avalanche Transceivers affected by Mobile Phones

A manufacturer’s investigation has revealed that the search mode of ARVA 9000 and Ortovox M1 avalanche transceivers can be affected by GSM mobile phones.

A pisteur died at Pra-Loup on the 25th of December. He was caught and buried in an avalanche while securing the ski area. His colleague tried to find him using an ARVA 9000 avalanche transceiver. The ARVA indicated a direction and distance that were incorrect, some 50 meters away from where the pisteur was buried. He was later found with a classic analogue avalanche transceiver but too late. Inquiries revealed that the searcher’s mobile phone was turned on and may have affected his avalanche beacon.

The search facility of ARVA 9000 and also the Ortovox M1 can be affected by mobile phones in proximity that are not turned off. After testing this problem has been confirmed by the manufacturers and by contributors to the fr.montagne Internet newsgroup. It would also seem that there is some affect on analogue transceivers. It is recommended that all mobile phones and other electronic devices within the search area should be switched off when a search is made.

Further Information: Pisteur Killed in Pra Loup

===== Update =====

It is over 5 years since we reported problems with mobile phones and certain digital avalanche beacons. There is still a lot of interest in this story and this page gets linked to so we thought we would follow it up.

Remember the problem only manifests itself when the searcher has both a mobile phone (switched on but not in use and not updating with the nearest cell) and a beacon in search mode. There is no evidence that a victim wearing a mobile phone interferes in any significant way with the searcher’s beacon. In our limited tests the problem of interference is also less marked with more recent twin antenna beacons. They are probably better able to distinguish between noise and a genuine signal.

This report was made after the Pra-Loup avalanche by Bernard Giraudon of Nic-Impex who produce the ARVA 9000, ARVA Evolution+ and ARVA A.D.Vanced avalanche beacons.

So what happened at Pra Loup? : this information comes from the report compiled by mountain police unit at Jausiers (PGHM) it seems that a dozen members of the Pra-Loup piste patrol went out on an avalanche control exercise. While descending one pisteur left the group and was buried by a slide. A little later one of the group noticed he had not arrived at the rendez-vous and climbed up to look for him. Seeing a recent avalanche he figured the man was in a dip whereas in reality he was 60 to 80 meters higher up on the slope. The group were equipped with 4 ARVA 9000 and 6 Ortovox and the victim had an old Ortovox F1. One of the rescue workers turned his ARVA 9000 to search mode but he also had a portable phone. He picked up a beep, the direction arrow flashed and the distance read 50 meters. He asked his colleagues to turn off their beacons so that the group could concentrate on his beacon (an error). The pisteur with the mobile phone, instead of realizing that he received one or two irregular beeps, that the LED flashed on and off and that the direction indication varied between 50 – 12 then 36 meters etc, evidence that there was interference, wasted 50 minutes before calling the PGHM. Arriving at the scene the police, realising the problem of interference and using an ARVA 9000 found the victim in a few minutes. The head of the piste patrol resigned following this incident.

Following this incident, and knowing that all beacons on the market (in 2001) were subject to interference from neon lights, high voltage lines, computers etc., we made some tests with beacons and portable phones and are conclusions are:

All current avalanche beacons suffer from interference from portable telephones but this varies according to the mobile phone and beacon (PH found the same in tests). The interference is generally in a range of 10-50cm but sometimes as far as several meters. Analogue beacons can pick up phantom beeps and the LEDS can flash randomly. Digital beacons emit random beeps and the direction and distance readings are unstable. It is important to note that a transmitting beacon is unaffected so a mobile phone on a victim should not cause any problems.

It is important to note that when members of the rescue services make a search with an avalanche beacon they ask for what is called “radio silence”, that is all electrical equipment in the search area must be turned off.

Bernard GIRAUDON (Société Nic Impex)

Immediately following the incident guides were advised to turn all mobile phones off in a group. Further testing has shown that to not be strictly necessary. However given the problem of reception in the mountains, the limited battery life mobile phones have in harsh environments, the chance that recreational user forget to turn off their mobiles and the problems recreational units encounter when confronted by confusing signals we recommend the default that all mobile phones should be off.

There is the counter argument that a mobile phone that is switched on can be used to locate a victim. To our knowledge there is one case of this in France, but that was after the police had exhausted other means. A mobile phone that is switched on can also give a stronger signal to a Recco receiver.

Further information:
Avoriaz Avalanche Victim Located by Mobile Phone
Avalanche beacons affected by LED head torches

Posted by davidof on Monday, 05 February, 2001 at 10:36 PM

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