November 15, 2019
In this video, BCA’s Bruce Edgerly covers the basic functions of an avalanche transceiver. He gives a great ‘how-to’ on flux lines, electromagnetic noise, and the reason for a third antenna.
Traveling in the backcountry with an avalanche transceiver is highly recommended (OK, we’re biased), but beacons will only help you and your group if you all know how to use them. To further your avalanche transceiver knowledge, BCA has created 12 new transceiver education videos for the 17/18 season: from the very basics to the very esoteric, including one on how to pass the transceiver portion of a guiding exam.
BCA’s “Introduction to Avalanche Transceiver for Skiers and Snowboarders” provides nearly everything you need to know about getting started with your transceiver. You’ll learn how to use your directional lights to follow electromagnetic flux lines. You’ll learn how to wear your beacon and how to keep it isolated from electromagnetic noise. The videos also clarify the importance of the third antenna, and how it cleans up the last few meters of the search to eliminate misleading “spike” signals.
Once you graduate from watching “Introduction to Avalanche Transceivers,” check out our new videos on how to do a transceiver trailhead test, advanced transceiver search techniques, and how to conduct a transceiver search in case of multiple avalanche burials. We also have a series on Tracker’s special functions, including Special Mode, Signal Suppression, and Big Picture. All of these can be found on our Videos page. For training videos about avoiding avalanches (the Backcountry Basics) and performing companion rescues, first aid, and evacuation, go to our Education page.
If you’d like to learn more, scroll down to read the full transcript.
Full Transcript: Intro to Avalanche Transceivers for Skiers and Snowboarders
Howdy, Bruce Edgerly here, Co-Founder and Vice President of Backcountry Access, in our backyard here in Summit County Colorado. We’re here today to talk about transceiver basics. We’re going to talk about the science behind transceivers, some basic concepts that apply to all transceivers really, and then we will go through beacon searching, probing, and shoveling technique in our 101 series: transceiver searching 101, probing searching 101, and shoveling 101. And then we have an advance video to watch, once you graduate from those videos. So let’s talk about transceivers.
Why do we call then transceivers? Because they transmit and they receive. We don’t call them transponders, and generally, we try to avoid calling them beacons because that can be confused with an emergency locator beacon, which is a completely different technology.
Alright, since its a transceiver, and we need to pull it out to receive a signal, we need to make sure it’s accessible. So, you always want to wear it underneath your outermost layer, so that it’s not fully exposed to get torn off if your in a violent avalanche, but it’s accessible enough so that you can pull it out and so that somebody else can pull it out and turn it off once they find you. Another place you could put it is in your side pants pocket, just make sure that pocket is built into the inside of the pants and not sew on the outside, and make sure that you clip it into the zipper area.
The golden rule for turning on your transceiver is put it on, turn it on and take it off, turn it off. In other words, turn it on when you put it on, don’t worry about wasting batteries because in transmit mode it should last up to 300 hours and transmit, so there is no reason to try to conserve batteries that will last most people an entire season. Another important consideration is to isolate your transceiver from other electronics on your body, like cellphones, GPS’s, or GoPro’s.
In Transmit mode, it doesn’t make a huge difference if they are right on top of each other, it could effect the shape of your search, it could effect your battery life a little bit, so it’s a good idea just to keep them a few inches apart 20 cm they say so that if you do get tumbled around in an avalanche, they don’t get shoved into each other. In search mode, you can have some effects: reduced range, possible false signals if they’re very close to each other. So we suggest making sure that in search mode you are at least 50cm apart from the searching beacon and any electronic device that you might have on you. But that’s good technique; you should be searching with your hands outstretched, so you are looking ahead of you and not getting fixated on the transceiver screen. If you do end up having to perform a search, generally you’re going to want to turn off all those electronic devices to prevent any complications.
Let’s talk about the transmit part of the transceiver. When you turn on any transceiver, you’re going to get a series of diagnostics. But the most important thing is the battery power, make sure you never go out there with your transceiver battery power of less than 40 percent, at least with the Trackers. Make sure you only use high quality, name brand alkaline batteries in your transceiver. Other batteries tend to have variations in the size and the resistance and then the rechargeable and lithium batteries tend to drop right off rather than having a gradual discharge curve, which makes it much easier to predict when your battery is going to die.
In addition to checking your battery power every day, we suggest a full trailhead test. There’s no substitute for a trailhead test in the morning where you check both transmit and search functions with everybody in your group. It’s more thorough than sending it back to the manufacturer for an electronic checkup and than just walking by a beacon checker at your local trailhead. All avalanche transceivers transmit the same way. They send out a beep every second or so, and the only difference between different brands is how fast the beep. Some go beep, beep, beep and some sound out a series of long beep, beeep, beeps. Other than that they are pretty much the same. In search mode, that’s where you’ll see a lot more differentiation. All transceivers, at least since 1996, transmit at the 457kh frequency, meaning they’re all compatible with each other and they all send out an electromagnetic field every second or so shaped like this (image appears on screen). What they do in search mode is steer you in along the so-called flux lines of this electromagnetic field. That’s why you notice that when you’re searching out in the field, you’re not always walking in straight lines, sometimes your walking in big arches. That’s because you are following those flux lines.
An important thing to remember is that this field, this electromagnetic field, is three dimensional. It’s like a big onion. So these curves are also in the vertical dimension, and this can make it a little bit complicated once you get in close. You’ll see with a single or dual antennae beacon when you get in close to the buried beacon, sometimes there’ll be a little hiccup, and this is just where the field lines are perpendicular to your horizontal searching transceiver, so it has a hard time picking the signal up strongly.
The third antennae is meant to align itself with the electromagnetic field better in those spots and therefore eliminate those hiccups which we sometimes call spikes. That’s all the third antenna does, is it cleans up the last few meters of the search and eliminates those little spike signals. The third antenna does not increase your receive range; it doesn’t help multiple burials; all it does is clean up the final fine search. You’ll notices that for this reason, most avalanche transceivers directional lights will turn off at two or three meters because when your in this close the field lines do get complicated and at that point your preforming bracketing instead of following the flux lines and you should be moving in perpendicular lines.
To summarise, these are the two most important concepts of the avalanche transceiver search. One of them is, to follow those flux signs, you need to follow the lights on your transceiver, and when the light goes left, you go left. You also need to make sure the numbers are going down; if they’re going up, it means you are going further away from the victim, and you need to turn around 180 degrees and go the other direction. The most important part and sometimes the more challenging part of the search is ‘the fine search.’ This is the part within three meters, and here you want to slow down.
When searching with an avalanche transceiver, we say “run, walk crawl.” In the first part of the beacon search, you’re running as fast as you can, then you want to slow down when you get to about ten meters, and then at three meters, you get into the fine search. This is where we want to get on all fours, and we want to crawl literally on the snow surface and get our transceiver as close a possible to the victim.
When we’re in the fine search, we perform a process called bracketing where we look for the lowest possible distance reading; we go past it to confirm it’s the lowest reading, then we come back to the lowest reading, and we go out to either side to see if there’s an even lower reading. During this bracketing process, it’s mandatory to keep your transceiver in the same direction. Don’t rotate it or sweep it because that will change the numbers a little bit, just keep it straight and follow perfectly straight lines the whole time. Make sure that if the terrain is uneven, or if there’s debris or a slope that you keep the transceiver up above the debris so your not moving it up and down and changing the distance readings, and make sure that you follow the snow surface, that your parallel to it.
It’s really important when you’re bracketing to make sure that you’re performing nice wide brackets, using your full arm’s length and extending your tether attaching your beacon to your harness, all the way rather than small little micro-movements. The more you outstretch your arms, the more distance information you’re going to get, and you’re going to be able to confirm whether or not you hit that lowest reading. Once you’ve confirmed the lowest distance reading, this is where we start probing; we’ll get into more detail on probing and shoveling technique in probing 101 and shoveling 101.