Item: AVALANCHE TRANSCEIVERS, ELECTROMAGNETIC INTERFERENCE AND THE 20/50 RULE
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Title: AVALANCHE TRANSCEIVERS, ELECTROMAGNETIC INTERFERENCE AND THE 20/50 RULE
Proceedings: International Snow Science Workshop Proceedings 2023, Bend, Oregon
Authors:
- Bruce Edgerly [ Backcountry Access, Inc., Boulder, CO, USA ]
Date: 2023-10-08
Abstract: Electromagnetic interference (EMI) is an increasing concern in the snow safety community, as it can affect the performance of avalanche rescue transceivers in the field. Not only is the number of users increasing in the winter backcountry, but these users are increasingly carrying electronic devices such as smartphones, smart watches, GPS devices, heated clothing, and electronic airbags. To better understand the effects of various EMI sources on avalanche transceivers and to provide clear guidance to the public, we undertook a series of tests on both active and passive sources of interference. The results confirmed that the "20/50 Rule" is an adequate, albeit conservative, measure for mitigating the effects of interference from most personal electronics. This rule-of-thumb advises users to keep all personal electronic devices at least 50 centimeters (one arm's length) from a transceiver in search mode and to keep these electronics at least 20 centimeters (one hand's width) from a transceiver in transmit mode. In the case of heated gloves, smartwatches, chest-mounted cameras, and chest-mounted digital UHF/VHF radios, it might be difficult for some users to achieve this distancing, in which case the noise source should turned off or relocated. The research indicated that snowmobile engines create more noise than personal electronics and that noise can persist as the user moves away from the operating snowmobile. Therefore users of a searching transceiver should turn off the engine or gain at least five meters distance from a running snowmobile before entering search mode. Since all avalanche transceivers display the strongest signal when multiple victims or EMI sources are present–and since interference sources are invariably weaker than a transmit pulse at close range–there were no effects on the search in the fine search phase of an avalanche rescue. In almost all realistic cases, a signal can be isolated over electromagnetic noise within a range of approximately ten meters. Environmental EMI sources such as overhead and underground power lines, electrical generating equipment, and even electrical storms, are more difficult to control. When experiencing effects such as false triggers and decreased receive range caused by environmental EMI, users should reduce their search strip width to a maximum of 20 meters during the signal search phase of an avalanche rescue.
Object ID: ISSW2023_P2.60.pdf
Language of Article: English
Presenter(s): Bruce Edgerly
Keywords: avalanche transceiver, avalanche beacon, electrical interference, electrical noise, electromagnetic interference, electromagnetic noise, EMI
Page Number(s): 997 - 1003
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