Behind the Beeps:
The Truth About Digital and Analog Avalanche Beacons
by Craig Dostie
from Couloir Magazine XI-5, Spring'99

With the advent of digital beacons and all the new features they have to offer, many old standards are being questioned. If you’re in the market for a beacon, the following guidelines may help you understand the differences between the options available.

ANALOG VS. DIGITAL BEACONS
All beacons transmit and receive analog signals. The difference is in the processing of that signal. Analog beacons convert the inaudible radio signal of the transmitting beacon into an audible tone, echoing the strength of the original, pulsed signal. Digital transceivers, on the other hand, sample the received signal digitally, perform a mathematical algorithm on that information, and then output visual and audio signals.

The real difference between beacons is not in the digital or analog processing of the signals, but in the beeps and flashes it emits to us, the searcher. Right now what we call digital beacons provide better visual clues with directional lights and a distance display, while their audible beeps are of varying value. Analog beacons rely primarily on the volume of an audio beep; they also have lights to indicate directional alignment with flux lines. The beauty of analog beacons is their simplicity: the closer you are, the louder they get. Their signals are easy to interpret even without much practice, and if you’ve had some practice, pinpoint searches are quick.

Digital beacons show direction with lights and display the distance to the victim in numerals on an LED or LCD screen (the numbers are not super accurate, but they’re good enough). In the case of Backcountry Access’s Tracker DTS, dual antennae help you stay perfectly aligned to the flux line of a victim, while Arva’s 9000 and Ortovox’s M1 only use one antenna. For the latter, arrows indicate when you’ve deviated from the flux line, but they are not as sensitive to changes as the Tracker DTS is. As a result, the Tracker DTS keeps you more precisely on the flux line, while other beacons guide you approximately along the flux line in a piecewise linear fashion (see "Tangent search" p 59). Digital beacons not only get you to the victim’s general vicinity fast, they also yield quick results in the pinpoint search. However, pinpoint methods differ. Using the same pinpoint method for digital and analog beacons will confuse most users.

By far the most significant difference between analog and digital beacons is the learning curve involved with using them effectively. In single-victim scenarios, digital beacons require far less practice to achieve good results than do analog beacons. The beauty of a digital system is that a signal can be processed and output in many different ways. In fact, now that digital processing has landed in the beacon world, it’s only a matter of time before we will be downloading software from a manufacturer’s Web site to find out about the latest way to find buried beacons.

RANGE
Clearly, range is important. But how much is enough? All beacons currently on the market meet European DIN standards. In transmit mode, all use a single antenna and have about the same transmit range. In receive mode however, the Arva 9000 and the Tracker DTS have a significantly smaller range. Competitors may claim that they don’t meet DIN standards, but this is incorrect. For single-antenna analog receivers the receive range is a fair indicator of sensitivity. With digital processing the apparent receive range is reduced, but the sensitivity is not. The key thing to keep in mind is that pure numbers about range or sensitivity aren’t all you need to know to determine which kind of beacon is best for you.

For instance, inexperienced users of analog beacons tend to move slowly through the medium-search range, carefully adjusting the volume as they get closer. With digital beacons, one never wastes time on this process or gets confused about how far to go. So while a digital beacon may take longer to pick up the first signal, that may not be a drawback, depending upon how quickly you move once you’ve found the signal. Where increased receive range has a clear advantage is in a search of a large avalanche path. More range simply allows you to cover more ground more quickly, whether you are a solo searcher or part of a group.

RANGE VS. ACCURACY
One of the key questions to ask in determining which kind of beacon you should be using is that of whether the first beep you hear, or the last, is the most important. It is easy to argue that knowing exactly where to start digging for a victim contributes more to his or her rescue. This assumes, however, that digging for the victim will take most of the time required to rescue him or her, and that receiving the first signal doesn’t take more than a few minutes. In the case of a small- to medium-sized avalanche, this may be true.

On the other hand, in a large avalanche you could spend an inordinate amount of time zig-zagging an avy path as a solo searcher with a short-range (digital) beacon until you picked up the first signal. If there are several searchers, beacons with a shorter range tighten the distance between searchers. For the best possible results, one would like a beacon in search mode to have both range and pinpoint accuracy. Analog beacons have the biggest range, but they require a lot of practice before they will yield reliable pinpoint accuracy. If you and your friends practice, get analog. If you keep meaning to practice more, the range limitations of digital are offset by a higher probability of good pinpoint accuracy. If I were buried, I’d want my friends, who rarely practice, to have digital.

ARE ALL BEACONS COMPATIBLE?
Except for the outdated 2.275 kHz models, every 450 kHz beacon on the market can find every other beacon. This doesn’t mean, however, that the beacons won’t discriminate among themselves. Last year it was shown that the Tracker DTS favored beacons with a faster pulse rate, like its own. Because of its method of digitally sampling the signal, it reacted more quickly to a signal that occurs more often. This could also mean that it would locate a Pieps (second-fastest pulse rate) over, say, the Arva, Ortovox, or SOS beacon. Since then the Tracker DTS has changed its search algorithm so that it now places priority on signal strength, not pulse rates—further proof that digital beacons can be more easily upgraded and improved than analog beacons can.

In the meantime manufacturers with the slower pulse rates may cry foul, but with the inevitable change in the wind, if more pulses give faster, more accurate responses, perhaps every manufacturer should consider making their beacons beep more. It should also be pointed out that this "beacon discrimation" is not something that has been newly discovered, since even analog beacons generally found the old Skadi beacon, which has a pulse rate three times faster than that of the Ortovox, more quickly. The only foreseeable problem with faster pulse rates is that in a multiple-search scenario one could easily become confused by a mix of faster and slower signals.

THE TANGENT SEARCH
For the past three years the tangent method of searching has been promoted as the quickest way to find a buried beacon. According to this method one aligns the beacon with the flux line of the transmitting beacon and then moves in that direction. With single-antenna beacons (digital or analog), alignment with the flux line is determined by rotating the receiving beacon until it provides the best signal (loudest tone, maximum number of lights on, and/or minimum distance reading at that location). One then walks in the direction of the best reception. By regularly correcting the alignment as you walk, you can move along the flux line directly to the victim. This is simple but requires practice, especially with the more audio-intensive analog beacons.

So far (1999), the Tracker DTS is the only avy beacon using dual antennas, which, because they can sense phase as well as field-strength differences, make the beacon more sensitive to flux-line changes and will likely keep a searcher more closely on the flux-line path. It’s sort of like the difference between seeing with two eyes versus with one. Because single-antenna beacons can only sense signal strength (loudness), they are less sensitive to flux-line changes and can allow the searcher to stray a bit farther from the line. Again, with practice, this problem can be minimized. Ortovox suggests following the mantra, "sweep slow, walk fast," for best results.

THE PINPOINT SEARCH
When you get within one to two meters of your victim, depending on depth, a grid search is recommended with single-antenna beacons. It is very important, at this stage, to maintain the orientation of the receiving beacon; that is, do not rotate it. With a bit of practice this works very well, but without it confusion often reigns. This is especially true when the buried beacon is pointing straight up. In that case, the signal directly over the buried victim is reduced. The Tracker DTS, on the other hand, thrives on vertical burials—or any fine search for that matter—as long as you follow the flux line all the way in. The key here is to not adopt a grid-search method, but rather to refine the directional aim of the beacon by tilting it into the snow as you get within one to two meters of the victim. (Tip: Try twisting the beacon 90° to see the alignment with the flux line from the side.) With either type of beacon, studies show that probing will probably yield a quicker find than will trying to refine the pinpoint search to a less than two-foot area. The beauty of the dual-antenna procedure is that it helps aim the first probe. It should be noted that it is also possible to use a single-antenna beacon in a tilting fashion to point to a buried beacon in a pinpoint search. And guess what? All it takes is more practice.

CONCLUSION
Now that the age of digital beacons has arrived, two questions arise. Which avalanche beacon should you buy, and when? For now, if you need a beacon, get one. If you are conservative, and prefer reliability, stick with analog beacons, and let price be your guide. If you’re willing to gamble that range is worth sacrificing for easier pinpoint accuracy, go digital. If you have a beacon already, be sure you and your regular partners practice often. If you are looking to upgrade you may want to wait a year. We’re not so sure that the market for avy beacons will ever be so big that the price will drop significantly, but it is easy to infer that in the years to come digital technology in avalanche beacons will improve greatly.

THE REVIEWS

ARVA
9000
Single antenna, digital beacon $299.95 220g Batteries: 3xAAA
Pros: Good harness system • on-switch integrated into harness • easiest to figure out for single victim scenario • no volume switches • excellent audio signal • good distance with acceptable direction visual indicators • endorsed by Rock & Ice magazine.
Cons: First year on the market • multiple victim scenarios require practice. 503-236-9552 • www.climbaxe.com

BACKCOUNTRY ACCESS
TRACKER DTS
Dual antenna, digital beacon $299 276g Batteries: 3xAAA
Pros: Excellent directionality • visual distance indicator • no volume switches • special narrow focus mode for multiple victim searches • auto-lock on strongest signal • fast pulse rate • harness allows tethered search at arms length.
Cons: Shortest receive range of the pack • audio signal weakest of the pack • harness needs work • multiple victim scenarios require practice. 800-670-8735 • www.bcaccess.com/bca

BARRYVOX
Dual antenna, digital beacon
Pros: Switchable from single antenna, analog mode to dual antenna, digital mode • company builds avy beacons for Swiss Army • works perfectly on paper.
Cons: Not available yet (not tested), multiple victim scenarios require practice.

ORTOVOX
F1
Single antenna, analog beacon $250 230g Batteries: 2xAA
Pros: Most popular beacon among professionals • excellent harness • on-switch integrated into harness • battery check • good audio sensitivity in close • Red-Yellow-Green signal strength LED’s • real-time audio beep.
Cons: Multiple victim scenarios require practice.

M1
Single antenna, analog beacon with digital display $300 230g Batteries: 2xAA
Pros: Superb harness system includes integrated on-switch • can turn on with or without harness • it’s an F1 with an understandable visual display • real-time audio beep.
Cons: LCD display needs external light and is visually cluttered • multiple victim scenarios require practice. 603-746-3176

PIEPS
OPTI 4 (OPTI FINDER SHOWN)
Single Antenna, Analog Beacon $249 230g(approx.) Batteries: 2xAA
Pros: Good Harness System, battery check • and 2 extra volume settings for better deep burial differentiation • four LED’s for visual signal strength • real-time audio beep.
Cons: On switch not part of harness • multiple victim scenarios require practice. 800-443-8620 • www.lifelink.com

SURVIVAL ON SNOW
F1-ND
Single Antenna, Analog Beacon $245 230g Batteries: 2xAA
Pros: Good harness system • automatic on switch integrated into harness • Red-Yellow-Green LED’s for visual signal strength • reduce volume indicator LED • real-time audio beep • economical.
Cons: Least sensitive visual indicators • multiple victim scenarios require practice. 403-973-5412 • www.sos-find.com

BIBLIOGRAPHY
Here’s where I did my research, plus a few tests in real snow, on a real avalanche slope, with novice and professional searchers. Read and think for yourself.

Bruce Edgerly and John Hereford, "Digital Transceiving Systems: The next generation of Avalanche Beacons."

Procedings of the ISSW Conference, Oct. 1998

Swiss Federal Institute for Forest, Snow and Landscape Research, "Summary of the Avalanche Beacon Test LVS-98,"

The Avalanche Review, Vol. 17, No. 3 - January 1999, pg. 3

1,3 Dale Atkins, "Companion Rescue and Avalanche Transceivers: The U.S. Experience,"
The Avalanche Review, Vol. 17, No. 2 - December 1998, pg. 9

Steve Matthews, "Transceiver Signal Strength: Batteries and orientation can make the difference," Snowboarder Magazine, October 1998, Pg. 168

Clyde Soles, "Avalanche Beacon Review," Rock & Ice Magazine #89, December 1998, pg. 2

Nic Seaton, "Digital Avalanche Rescue Transceivers: Are we ready for the transition?,"

The Avalanche Review, Vol. 16, No. 6, June 1998, pg. 10