Get Outdoors - Women: Avalanche Beacons

What They Are and How They Work

An avalanche beacon (or transceiver) is, or used to be, a simple radio transmitter and receiver - sending or receiving a beeping signal on a standard frequency of 475 megahertz. When someone wearing a transmitting beacon is buried by an avalanche, their transmitter continues to emit "beeping" signals which can be picked up by a searcher/rescuer who has another beacon set to receive the signals. These signals become stronger as the rescuer gets closer to the buried unit, allowing the rescuer to zero in gradually on its location and find the buried wearer.

The Evolution of Beacon Design

Avalanche beacons have evolved and improved over the years, with each innovation designed to make them easier to use. This is important because they are actually quite difficult to learn to use, requiring a fair bit of training and a great deal of practice in order to quickly find a buried beacon.

Until recently, the most important design change was the addition of colored lights to the unit, indicating visually the change in volume of the signal as the searcher got closer. Since changes in volume can be hard to detect, this visual reinforcement proved quite helpful.

More recent innovations include adding a second antenna and digitizing the signal with a micro processor in the unit. Backcountry Access introduced the digital technology with the "Tracker". Unlike the traditional "analog" transceiver, the Tracker's micro processor, in combination with two antennas, allows it to analyze the incoming signal for the user, calculating both direction and strength of signal. It then displays the signal as a numerical readout indicating distance from the target and "points", by means of an array of lights, in the direction the searcher needs to turn. The searcher no longer uses her ears to listen for a change in volume, she just reads the numbers on the screen and walks in whichever direction makes them grow smaller, turning right or left as indicated by the lights. The unit does the work that used to be done by the user's ears, eyes and brain.

Beacon Manufacturers and their Designs

Various beacon manufacturers have responded to the challenge of the new digital technology in different ways.

Ortovox has kept the "analog" technology - direct signal to the user with no intervening processor, single antenna - while digitizing the display to make it easier to use. The signal is displayed on a small screen as a numerical display giving distance to the target, and volume is also indicated by a bar that fills more completely as the signal gets stronger. A light also echoes the indication of closer range. The Ortovox strategy is to display information in several ways, since individuals differ in the ways they process information most effectively. The analog technology doesn't indicate direction as effectively as the digital units, but the Ortovox unit does indicate direction in a "yes/no" sort of way by having an arrow that fills in when the receiving unit is aligned with the radio waves coming from the transmitting unit.

Barryvox has embraced the dual antenna, digital design. However, recognizing the diversity of peoples' perceptive styles as well as the reluctance of experienced beacon users to abandon acquired skills and habits to learn new ones, they have attempted to provide a choice between direct signal (analog) modes where the signal is processed by the users' own ears and brain, and the directional ability of the digitized signal.

Choosing the Right Unit

Here are some pros and cons of the new digital, dual antenna design:

Cons:

Reduced range: The addition of the processor seems to have reduced the range of usable reception significantly. (The Barryvox so far is worse than the Tracker in this regard). This could be a distinct disadvantage in a large search area, or when the rescuers didn't see the burial. It's hard to say how important this is - in other words, how much range does one actually need in practice?

Less effective with multiple burials: If more than two people are beneath the snow, the task of separating and identifying the different signals becomes much more difficult with a digital readout than with an audible signal. Our ears are pretty good at differentiating between the relative strength of several signals and picking out the loudest, and the digital unit doesn't allow the user to do this. With training, a digital readout user can learn to differentiate and identify a single signal out of several, but it is not as easy as with an audible signal.

Pros:

The digital unit is simply much easier to learn and to use, especially with a single burial. One guide tells a story of giving his 9 and 11 year old niece and nephew two simple instructions: keep the light in the middle, and make the numbers get smaller - and they found a buried beacon in 90 seconds! Since survival rates of buried victims decrease dramatically and exponentially after 10 to 15 minutes of burial time, and skiers and other winter fun-hogs hate to take time away from the good stuff to practice beacon searches, this is an important difference for the recreational user.

The Upshot:

Many professional users highly trained in the use of avalanche beacons, such as guides, ski patrollers and other avalanche professionals, may be more likely to prefer an analog beacon. But for the recreational user, who doesn't care to invest a lot of time learning to use a traditional beacon, or who has received only minimal instruction, the digital, dual antenna technology is a better choice.