If caught and buried in an avalanche, you have a 50-percent chance of surviving. Out of those on the wrong side of chance, 25-percent die from trauma and the other 75-percent die from suffocation. Wearing an avalanche beacon increases your odds of surviving an avalanche burial, if you and your partner each have a good beacon and know how to use the technology properly. The latest step in beacon technology, the addition of a third antenna, also will help you and your partner avoid that 37.5-percent chance of suffocation.

How Beacons Work
Avalanche beacons are a type of radio transceiver that send and receive signals. They are the size of a small PB&J sandwich, typically weigh 10-12 ounces, and have a weatherproof, hard exterior designed for tough winter conditions.

“Beacons consist of antennas and software. They crunch the numbers and give you info that is useful,” said Ethan Greene, director of the Colorado Avalanche Information Center located in Boulder. Inside modern avalanche beacons are two or three internal antennas. When traveling in the snowy mountains you set the beacon to “transmit” and it sends a 457 kHz signal from one antenna. When a victim is buried, rescuers switch their beacon to “search” and the searching beacon receives signals on all antennas.

First generation beacons, such as the Ortovox F1, used a single antenna that sent out an analog (real-time, unprocessed) signal. Rescuers received this signal as an audible signal – searches were done by moving toward the loudest signal.

In 1997, the manufacturer Backcountry Access introduced the first dual antenna beacon: the Tracker DTS, which calculated a direction to the transmitting beacon through internal software. Many praised the Tracker’s simplicity, saying you could hand the Tracker to an untrained user, tell them to follow the arrow, and they could find a victim. Some professionals discredited the Tracker DTS by saying its tendency for dead spots – meaning when the beacon shows no reading because of crossed signals – was too high for reliability. Despite these problems, almost all beacon manufacturers began using dual antenna technology.

Three Antenna Beacons
The most recent development in beacon technology is the addition of a third antenna. “Three antennas give you more resolution because they have the X, Y, and Z directions,” said Greene. Many models currently have a third antenna: Barryvox Pulse, Pieps DSP, Ortovox Patroller (formerly X1), D3, and S1.

The main purpose of the third antenna is to eliminate spikes in the fine search phase. A spike is when your beacon leads you to the strongest signal that is near, but not directly above, the victim. “The third antenna has nothing to do with multiple burials or max range,” explained Bruce Edgerly, director of Backcountry Access. “It’s only about smoothing out the pinpointing process so that you don’t have any spikes, or what people used to call nulls. A null is when an analog beacon loses the sound because the signal is weak in that direction.”

The transmitting antenna in a beacon sends out a signal shaped like an apple core. “The reason we get spiked signals is because the receiving beacon is perpendicular to the transmitting beacon’s electromagnetic field at some point on the way in,” Edgerly said. “The third antenna is able to align with the perpendicular part of the field so we don’t have a weak signal. That’s the concept behind a third antenna.”

“The key point to remember is that a third antenna and marking/masking feature on some beacons are not linked,” said Jonathan Shefftz, an AIARE* instructor, who has a detailed beacon review on WildSnow.com. Marking, also known as masking, is a feature on some newer beacons for multiple burial situations that allows the transmitting beacon’s signal to be blocked out once a probe strike has been made, allowing searchers to move onto other victims.

Beacons are not avalanche deflectors. If you’re heading into the snowy backcountry with a new partner, ask them: “When was the last time you practiced with your beacon?” If they say less than three months, stop right then and practice. Even if beacons become an iPhone app, complete with distance, depth, and pulse display of multiple victims, you'll have to keep practicing.

*American Institute for Avalanche Research and Education

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