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Feb 29 2012

Time to retire your beacon?

While testing avalanche transceivers this year it has become more evident that older, analog type beacons should be retired. It isn’t because they don’t work. But the way they work can cause trouble in the dreaded multiple victim scenario. If you have more than one person buried in an avalanche the odds are at least one person will turn up dead.

Screen capture of the received signal from an analog beacon. Notice how the signal never fully turns off - and the extra wide pulse increases the chance of signals overlapping.

Analog beacons should be retired because they transmit with a continuous carrier signal which, when you are close, can confuse searchers by covering up the signals from other, more distant victims. With a continuous carrier signal the oscillator that creates the 457 kHz signal is always on. When the pulse is ON, it connects the signal to the antenna so it radiates in to space. When the pulse is OFF, the antenna is switched off, but the signal is still being generated and it leaks out from the circuit board of the transceiver.

When you are within 2 meters the strength of the signal from an analog beacon is stronger than the ON pulse of another beacon that is approximately 30 meters away. That distance, of course, depends on spatial orientation.

By comparison, with modern digital beacons when they’re off, there is no signal being created. The oscillator circuit that generates the 457 kHz signal is not producing a signal until it is time to turn it on and transmit it. Notice how small the line is between pulses for the digital beacon compared to how fat is is for an F1. The height of the pulse and corresponding lack or presence of it between pulses indicates the strength of the signal between pulses.

Received signal from a recent model digital beacon. Notice how little signal there is between pulses? And how narrow each pulse width is?

There is another reason too. Not only is the signal not completely off when it isn’t transmitting, when it is on, it is on for approximately twice the time a current model “digital” beacon is on, which increases the likelihood that there will be an overlap in the timing of signals. This creates another source of confusion for the receiving transceiver, and more importantly, the searcher.

The end result is avalanche transceivers that are great at detecting and helping you find multiple victims, like Barryvox’s Pulse and Element, the Pieps DSP and DSP Tour, and Ortovox’ S1 can become “confused,” which inevitably slows down search times and compromises a victim’s survival chances.

Now I’m not advocating for some rule or law from higher up, I’m just encouraging you that if your avalanche transceiver is an Ortovox F1 Focus, a Pieps 457, or an Arva 457, please upgrade your beacon. You may appreciate it some day, and if you’re caught with another friend they most certainly will appreciate that. And don’t sell ‘em to a stranger either. If you can’t bring yourself to trash it, use it for multiple beacon searches and you’ll see what I mean by how easily it confuses you and others. When you’re frustrated enough, take a hammer to it.

In keeping with that sentiment, this is the last season you can buy an Ortovox F1, but don’t; let someone else make that decision.

© 2012
 

  • http://www.thompsonpass.com Valdez Telehead

    I would add a Tracker 1 (DTS) on your list of beacons that should be retired. I consistently have some issues with it in drills with folks who still have it. There are lots of them out there, perhaps more than any other beacon. Tracker 2 is great.

  • http://www.earnyourturns.com Dostie

    What sort of “issues?”

  • http://www.thompsonpass.com Valdez Telehead

    I have a DSP and over and over when doing beacon checks, etc….no signal, erratic signal when doing multiple searches. They do OK in single scenarios. Sometimes they work ok, sometimes not. I am not a beacon expert like some, but I have to manage groups of skiers with concerns about who is wearing Tracker 1′s. In other words I don’t rely on me being able to find a T1 as well as others. It might be that DSP just doesn’t like T1′s.

    The other day I was doing beacon tests, not knowing what beacons folks had. When the test was over, I guessed correctly who was wearing a T1 due to “issues”.

  • teletilyouresmelly

    How about m2s?

    I have an old (1992)F2 that I loan to hut trip members who don’t have a beacon and wouldn’t know how to search with a good one anyway- maybe I should stop that practice?

  • http://www.earnyourturns.com Dostie

    Well it seems you should at least upgrade that loaner to F1 quality. ;) That F2 would be an excellent avy placebo on a good spring corn day.

  • bob

    is it fate or serendipity . . . I’m a novice BC skier (who wants to live to be just an old BC skier) and bought a used Ortovox F1 off someone a few years ago . . . never needed it luckliy, but I have been trying to step up my commitment to the snow and wondering if I should buy a new beacon . . . and just found myself on your page tonight (skipping over from Wildsnow) . . . and okay, I’m gonna spend the money. Thanks for the information.

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