» Back to Articles List

Avalanche beacons - frequency drift - important!

It is a well-known fact among backcountry professionals but not so much among recreational skiers that over time any avalanche beacon will drift from its original frequency. What does it mean for you? It means that if your avalanche beacon drifts off the standard frequecy too much it may be no longer useful as your life saving device.

Avalanche beacon frequency background

International standard transmit frequency of a brand new avalanche beacon is 457 kHz. The worldwide frequency standard (457,000 cycles per second) was established in 1997. The tolerance allowed under this standard was tightened in 2001 from 457,000 +/- 100 Hz to 457,000 +/- 80 Hz.

This assures that all avalanche beacons are compatible thus in case of an avalanche accident you can search for Ortovox beacon with BCA Tracker and vice verse. This applies for all brands and models of avalanche beacons.

Ortovox avalanche beacons
Ortovox F2 analog avalanche beacon released in 1980.	Ortovox S1 is the first sensor-controlled avalanche victim scanner to be released in November 2006.

Avalanche beacon frequency drift

In 2001, the French Avalanche Research Institute's report revealed that the transmit frequency of some avalanche beacons at the time could significantly drift at cold temperatures.

The frequency drift can be experienced with any avalanche beacon after few years of use. Therefore we strongly advise that if your avalanche beacon is more than 3 years old you contact the manufacturer and ask him where you can have your beacon tested to assure there are no significant drifts.

Transmit frequency and receiver bandwidth

Avalanche beacon transmit frequency is only one part of the equation because avalanche rescue search is at least a two beacon process - one transmits (the victim) and one receives (the rescue party).

Even if an avalanche beacon transmits way off the allowed margin of the standard transmit frequency it may still be possible to receive its signal if the rescue beacon has such a wide receive bandwidth.

To avoid relying on such chances or coincidence it is a responsibility of each individual that uses avalanche beacon or transceiver to make sure his beacon is compatible. Have your beacon tested before every winter if it is more that 3 years old or buy a new beacon every 3-4 years.

According to a research report by Bruce Edgerly & John Hereford: "In the recent development of modern transceiver technology, there has been a direct tradeoff between ease-of-use and receive range [distance]. Easy-to-use digital beacons provide less receive range than analog beacons because the microprocessor must filter out extraneous electromagnetic noise before showing the user clear distance and directional information. Despite this tradeoff, all major beacon manufacturers are focusing their design efforts on increasing ease-of-use instead of range, as ease-of-use is where the market has shown the most interest."

If you are planning purchasing a new avalanche beacon bear in mind the ease-of-use should not be the ultimate deciding factor but rather research what is the range (in meters) of the avalanche beacon you want to have. Shop for new avalanche beacons.

Read the full report about avalanche beacon frequency drift by Bruce Edgerly & John Hereford: Obsolescence and Analog Avalanche Transceivers: Ensuring Downward Compatibility.

Back to top | Disclaimer | Copyrights