Backcountry series: History of the avalanche beacon
Colorado Ski & Snowboard Museum
The following is part of a series of articles compiled by the Colorado Ski & Snowboard Museum and Hall of Fame that will take a closer look at the sport of alpine ski touring. The museum is located atop the Vail Village Parking Structure and features a treasure trove of ski history and heritage.
Wearing an avalanche beacon in the backcountry, just like buckling a seatbelt in a car, is a matter of common sense. But, while neither will stop an avalanche or an auto accident from occurring, they will greatly increase your chances of survival and well-being if such an event does take place.
Avalanche rescue beacons have become standard equipment for skiers and snowboarders that venture into wilderness areas or beyond the boundaries of ski resorts. The small radio transmitters, strapped to the body, can aid rescuers in locating someone buried under several feet of snow.
Statistically, 92 percent of avalanche victims survive if they are dug out within the first 15 minutes. That percentage drops dramatically to 35 percent after 30 minutes. After an hour, only about 25 percent remain alive, and after two hours, almost no one survives.
The first truly practical electronic avalanche rescue beacon, called the Skadi, was created in 1968 in Buffalo, New York by a Cornell Aeronautical Laboratory research team, headed by Professor John Lawton. Prior to Lawton’s work, researchers had managed to develop electromagnetic methods to locate avalanche victims, although their products lacked enough range and accuracy to deliver the timely location required to save lives.
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Lawton’s Skadi evolved from a culmination of ideas and experimentation involving a number of people, most notably, well-known avalanche expert Ed LaChapelle. LaChapelle was working in Alta, Utah in the late 1960’s, involved in the development of avalanche safety ideas and techniques, including methods for finding buried victims.
In conjunction with his study, LaChapelle built a pocket-sized radio transceiver that worked at the upper end of the broadcast band. The idea was to be able to pick up the signal with a portable radio receiver, using the receiver’s antenna for directivity. Lawton, who happened to be skiing at Alta, saw LaChapelle conducting his experiments and figured there might be a better way.
Back in Buffalo, he assembled a pair of units using an audio frequency induction field. The device consisted of a pocket transmitter, about the size of a cigarette package, with a plug-in antenna in the form of a wire coil. The antenna was about a foot in diameter and sewn into the back of a parka. Not only did the unit work but the large coil antenna provided more range, although it also proved awkward to use, while obviously limiting the user to the chosen parka.
Lawton managed to downsize the unit by eliminating the parka antenna and replacing it with a smaller one built into a handheld plastic box. Just as in today’s avalanche beacons, the original Skadi radiated a magnetic field by pulsing electricity through a copper coil. Reception was achieved by picking up the magnetic field and producing sound in a small earphone.
The Cornell team put a good deal of time and effort into the method of finding a buried unit by receiving the transmitted signal. Their simple method, which found its way into virtually all later beepers, was to give the user an audio signal and a volume control.
The researchers selected a frequency of 2.275 kHz, which is audible to the human ear, eliminating much of the expense and complexity of a radio transceiver that had to convert a non-audible signal to a tone that could be heard.
The frequency that Lawton chose was virtually free of interference and worked well when blocked by objects such as rocks and trees. Due to greater range, a higher frequency of 457 kHz became the international standard in 1996.
When units were closer together, the signal was louder and, by using a grid search pattern, a searcher could home in on a buried victim by listening for volume changes. The human ear is more sensitive to such changes at lower levels so the volume control was constantly turned down as the signal got louder, allowing for precise location of the source.
The first production units of the Skadi were put on the market in the early 1970s and featured a long-lasting battery and an approximate 90-foot range. Due to the red color of the box, and its curved corners, users nicknamed it the “Hot Dog,” or “Hot Dog Skadi”.
The device quickly became standard issue for professionals such as ski patrollers, search and rescue volunteers and operators of slope grooming equipment who found themselves at risk of avalanche burial. The Skadi worked and it saved lives.
Soon, it was copied and improved by European manufacturers that converted to more streamlined models, built around replaceable AA batteries, rather than built-in re-chargeable batteries. Today’s state of the art beacons feature three antennas which, combined with the trio of antennas used in the receiver, reduce dropout problems.
The digital avalanche beacons on the market today incorporate microprocessors to simplify searching while containing a number of additional features, but all of them work on similar principles to the original Skadi. However, no matter how fancy a product you decide to purchase, training and practice are still essential elements in optimizing your avalanche beacon’s effectiveness in the backcountry.