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Electromagnetic Compatibility of Avalanche Beacons

07 Feb 2009

Lawine_Piepssuche_Bergrettung_Salzburg

Considering the recent public discussion on the EMC (ElectroMagnetic Compatibility) of some ava- lanche beacons, we state that

  1. All electronic devices are subject to EMC issues. Various types of interaction are possible, e.g. via RF radiation, static magnetic fields or even by the presence of materials with high magnetic permeability near a device.

  2. Interaction is not limited to particular products from specific manufacturers; it can be observed among all products with similar characteristics.

  3. All avalanche beacons use antennas made of a ferrite rod and a coil, and such antennas are tuned to the nominal operating frequency of 457 kHz. Any piece of material exhibiting signifi- cant magnetic permeability near the antenna of an avalanche beacon may detune the antenna and thus cause a reduced performance in terms of transmitted signal strength or receiver sen- sitivity.

  4. Some products use a combination of a Reed contact and a small permanent magnet to achieve waterproof switching of the main functions OFF - TRANSMIT – RECEIVE. Such de- vices may be sensitive to magnetic fields emanating from other devices, such as small loud- speakers in portable radios, detached speaker-microphones or even magnetic button closures on garments or magnetic name tags. However, such interaction is limited to very small dis- tances, usually below 4 inches (10 cm). In case of an avalanche, the position of an avalanche beacon relative to other devices may not be under control. It is very simple to determine a minimum distance for no interaction by a practical test using the devices under investigation.

  5. Users of avalanche beacons should carefully read the owner's manual that came along with the beacon and watch for statements about EMC.

  6. The best way to avoid any EMC problems is to keep devices separated from each other as much as possible.

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