Avalanche transceiver

Avalanche transceivers are a class of radio transceivers specialized to the purpose of finding people or equipment buried under snow. They are variously called "ARVAs" (Appareil de Recherche de Victimes en Avalanche, in French), "avalanche beacons" or "avalanche transceivers" with many regional slang terms in effect. When transmitting, the device emits a pulsed signal which another transceiver can receive. Due to the nature of the radio pulse, a person holding the receiving beacon can orient it, and "home in" on the location of the transmitting beacon using techniques similar to radio direction finding.

The current standard [ASTM'02] specifies a frequency of 457 kHz, and many companies manufacture beacons that comply with this standard.

It is important to note that an avalanche beacon is not considered a preventative measure for possible avalanche burial, but rather it is a way to reduce the amount of time buried.

History

In 1968 Dr. John Lawton invented the first avalanche effective transceiver [AlpenGlow] in 1968 at Cornell Aeronautical Laboratory in Buffalo, New York, with the first units being sold in 1971 under the “Skadi” brand name. [AlpenGlow] This unit, functioning on 2.275 kHz, converted the radio frequency to a simple audible tone that a human can hear. By following the tone to where it was louder, the beacon operator could use it to locate the buried beacon by using a grid searching technique.

In 1986 IKAR adopted 457 kHz.

In 1996 ASTM adopted the 457 kHz standard.

Standard: [WildSnow.com]
* 457 kHz
* 200 hours transmitting at +10C
* 1 hours receiving at -10C
* operation from -20C to +45C
* carrier keying (pulse period) 1000 ms +/- 300ms
* frequency tolerance +/-80 Hz

Types of Beacons

There are two types of avalanche beacons: digital and analog. They both adhere to the international standard as described above, and only differ in the method(s) used to indicate to the user where the buried beacon is located.

Analog

The original avalanche beacon was an analog beacon which transmitted the pulsed signal as an audible tone to the user. The tone gets louder when the user is closer to the transmitting beacon. These beacons have also been augmented with LEDs that provide a visual indication of signal strength, and earpieces to increase the ability of the listener to hear the tone.

Digital

Digital beacons take the strength of the signal and the emitted dipole flux pattern and compute distance and direction to the buried transceiver [ISSW 2000]

earch Techniques

Due to the highly directional nature of the 457 kHz signal at the ranges common for avalanche burial (and the range specified in the standards), there have been many techniques developed to search for buried beacons. Good beacon search abilities are considered a required skill for recreational backcountry skiers, mountaineers as well as avalanche professionals such as ski guides, ski patrollers, search and rescue volunteers and professionals. Recreationalists and professionals alike take part in drills, practice and scenarios as a regular part of avalanche skills training.

The burial of a single beacon may involve search using one of several methods:
* grid search
* induction search
* circle method

These search methods are adapted and extrapolated to scenarios where there is more than one burial.

Manufacturers

* [http://www.ortovox.com Ortovox] - "F1" (analogue) "M2", "X1", "S1", "d3" (digital)
* [http://www.pieps.com/ Pieps ] - "457", "OptiFinder" and "Opti-4" (analogue) and "DSP" (digital)
* [http://www.bca.com Backcountry Access] - "Tracker DTS" (digital)
* [http://www.survivalonsnow.com/ Survival On Snow] "SOS F1ND" (analogue)
* [http://www.mammut.ch/ Mammut] - "Barryvox Opto 3000" and "Mammut Pulse"
* [http://www.nic-impex.com/ Nic-Impex] - "ARVA Advanced", "ARVA 8000", "ARVA 9000" and "Arva Evolution+" beacons

Notes

References

*cite journal
author = ASTM International
date =
year = 2002
month =
title = Standard Specification for An Avalanche Beacon Frequency
journal =
volume = ASTM F1491-93(2002)
issue =
url = http://www.astm.org

*cite web
url= http://standards.mackido.com/en/en-standards24_view_5066.html
title=EN Standards: EN282:1997
accessdate=2007-04-21
work=
date=1997

*cite web
url= http://webstore.ansi.org/ansidocstore/product.asp?sku=ETSI+TS+100+718-v1.1.1-1999-01
title=ANSI Standard: ETSI+TS+100+718-v1.1.1-1999-01
accessdate=2007-04-21
work=ANSI
date=1999

*cite web
url=http://www.wildsnow.com/articles/skadi/skadi_1.html
title=The Skadi Avalanche Rescue Transceiver
accessdate=2007-04-21
work=WildSnow.com

*cite web
url= http://www.alpenglow.org/ski-history/notes/period/summit/summit-1970-79.html#summit-1971-mar-p29
title=Aplenglow Ski History
accessdate=2007-04-21
work=Summit Magazine
date=1971

*cite web
url= http://www.autocall.ch/media/documents/publikationen_standards_2000.pdf
title=European Law and Standards Affecting Avalanche Beacons
accessdate=2007-04-21
work=
date=
format=PDF

*cite journal
author = J. Hereford and B. Edgerly
date =
year = 2000
month =
title = 457kHz Electromagnetism and the Future of Avalanche Transceivers
journal = International Snow Science Workshop (ISSW 2000)
volume =
issue =
url = http://www.bcaccess.com/documents/457andFuture_000.pdf
format = dead link|date=June 2008 – ^{[http://scholar.google.co.uk/scholar?hl=en&lr=&q=author%3A+intitle%3A457kHz+Electromagnetism+and+the+Future+of+Avalanche+Transceivers&as_publication=International+Snow+Science+Workshop+%28ISSW+2000%29&as_ylo=2000&as_yhi=2000&btnG=Search Scholar search]}