ISSW 2012: avalanche beacons and electrical interference
Posted on November 19th, 2012 by edge | 8 Comments
We’re not done yet with our blog series on ISSW! Here’s a summary of the presentation by John Barkhausen on how electrical interference can affect avalanche beacons.
You might have seen some of the posts on TGR (Teton Gravity Research) and other forums recently in which a chap with a British accent (Stuart Pitches, fun co-owner of English retailer Facewest ), encounters problems when avalanche beacon searching with a GoPro camera attached to his chest. The video reinforces the point that electrical devices can definitely affect avalanche transceiver performance. But how much?
Barkhausen, a student at Alaska Pacific University, attempted to answer this question at the ISSW (International Snow Science Workshop) by placing various electronic devices near a transmitting avalanche beacon and near a searching avalanche beacon. Then he determined how it affected both the receive range and the search pattern of the receiving unit. He tried this with a cell phone, iPod, digital camera, RFID tag (Alyeska lift ticket), Spot emergency locator, a GPS unit, and a small radio. For searching beacons, he used a Tracker DTS, Barryvox Pulse, and Pieps DSP.
His first finding was that these electronic devices have no affect on a transmitting beacon, which is consistent with our experience. His second finding was that these electronic devices can definitely throw off the transceiver search if they’re held within 40 cm (about 17 in.) of the receiving unit. This is also consistent with our experience, which is why we recommend in our owner’s manuals to keep all electronic devices at least 30 cm (about 12 in.) away from the searching unit–or turn those electronic devices off entirely. In other words, keep your searching avalanche transceiver at arm’s length if you have a GoPro on your chest and you can’t figure out how to turn it off.
What are the symptoms when your avalanche beacon receives electrical interference? It will either lose receive range or it will show you “false triggers” on the distance display. This is usually in the form of erratic distance readings and directions; the distance readings are usually quite high, but not always. Can you avoid this if you use an analog beacon (like an Ortovox F1 Focus) ? Not really. You’re going to get so much static that you won’t even be able to pick out the “beep” in the background.
Barkhausen tried to capture this by tracking his search path on a GPS with each receiving unit (the person holding the GPS was well behind the searcher, for the reasons above). Unfortunately, this part of the study was not conclusive.
In a previous blog, we gave a good example of how electrical noise from a snowmobile engine can affect searching with an avalanche transceiver. Moral of that story: get off your sled if you plan to do a beacon search.
OK, so which beacons are less susceptible to false triggers and range loss than others? It’s clear in the snowmobile blog above. At ISSW, Barkhausen didn’t go there, but of course I had to follow up with him. He provided the following graph:
You’ll also notice that the iPod (orange line) and the GPS (red line) are the biggest culprits in creating interference, which is consistent with our experience.
So we give John an A- on his paper. His findings make good sense, although they could have been presented more clearly. He definitely reinforces what we’ve been saying for years: keep your searching beacon at arm’s length!
We’re looking forward to the next installment of John’s research at the ISSW 2014 conference in Banff.