Tips & Information » Avalanche transciever rescue techniques » Speeding Things Up - Loudspeakers and Induction Line Tangent
- The new single frequency (457 kHz) transceivers come with some changes that can make the first two phases of your search go much faster.i.
- Based upon range tests we conducted between the Ortovox F-2 (dual frequency) and F-1 (single frequency) transceivers, we estimate a 50% or so increase in the receiving range of the F-1 compared to the F-2. (We didn't notice any significant difference in the transmitting ranges of the two units.) This means you should pick up your first signal from the buried transceiver more quickly, and it should allow the rescuers to open up the search pattern (zig-zag or fall line) affording coverage of the same avalanche area with fewer passes.
- Most of the new transceivers come with a loudspeaker, eliminating the need for an ear phone. This avoids the frustrating interruptions frequently caused by having the ear phone drop out of your ear. Also, as mentioned below, it allows you to let the transceiver hang from your neck while you ski, freeing up both hands to grip poles and let you ski in a natural stance.
- It appears that the circuitry of the new transceivers has been modified to be more sensitive to the orientation between the search transceiver and the buried one. This makes it easier (along with the lights and "arrows" that have been added) to detect and determine the line of the tangent to the electro-magnetic induction line being emitted by the buried unit. This, in turn, makes it easier to learn and become competent in the induction line tangent search technique.
- During phase 1 of your search (executing your search pattern, listening for that first signal from the buried transceiver), you can leave the F-1 transceiver around your neck, either outside of your jacket or with your jacket open, so you can hear the loudspeaker. This keeps your hands free, allowing a more natural and speedy skiing stance, or to help you move rapidly through the ruble of avalanche debris. The loudspeaker and greater reception range of the F-1s contributes to a faster phase 1 search. It shouldn't have to be said, but we will anyway: make sure your reception strength dial is at maximum volume, and the speaker is aimed out, away from your body.
- Phase 2 begins when you get your first signal. The enhanced sensitivity of the new units to orientation with the induction lines means that you can scrap (at least at this stage of the search) the classic transecting-grid-in-search-of-fade-point method. Instead, follow the induction lines.
- When you get the first signal, orient your beacon (holding it in the horizontal plane). The signal strength (sound from loudspeaker, lights, arrow) will be strongest in two directions, 180. opposite of each other (this is the tangent of the induction line of the signal from the buried beacon). Head off in one of the directions (if you've done phase 1 properly, the preferred direction should be downhill). If the signal strength begins to fade, kick turn 180. and move in the opposite direction. The signal strength will increase as you move toward the buried transceiver.
- If the signal strength is increasing, keep moving, as fast as terrain and skiing skills permit. While moving, sweep your beacon in front of you, side to side, 45. to the left, then 45. to the right of your direction of travel. (Don't over sweep the beacon because there is another tangent and strong signal at your back (180.), and you don't want to be misled by picking it up.) The signal will fade to your left, and fade to your right, so keep on truck'n right downthe middle. With practice, it becomes automatic; the sound just sucks you along toward the buried transceiver. This part of the search can be conducted very rapidly.
- Remember - you are following the tangent of a curving induction line, so don't expect to be moving constantly in a straight line. More likely, you'll be moving in an arc. (As always, however, there are exceptions: if the buried transceiver is vertical (perpendicular to the snow surface), your induction line tangents could be leading you straight to the victim, without any noticeable curvature to your line of travel. If that's the case, go with the flow. Don't waste any time being confused by it all.)
- As signal strength increases, turn down the volume. The lower volume makes it easier for many to detect the fading to the left and right of the line of travel. The lower volume will also pay off when you complete phase 2 of the search, and switch into the fine grid pattern of phase 3.
- How long do you continue with the induction line method? Easy! For as long as it continues to produce results for you. As you move through phase 2, you will be rewarded constantly by an ever-stronger signal as you pursue your line of travel - until it stops!! At some point, the signal will drop off - not get stronger. This is the end of phase 2 and your induction line journey. Now make the transition:
- First, don't stop immediately. This could be a fade point, indicating that you have passed beyond the buried unit. But it could also be a null point. For example, if the buried unit is vertical, pointing perpendicular to the surface, you could be right in the null zone where there is no received signal. You could be directly over the victim. To eliminate the null possibly, "punch through" the fade point: continue beyond for another 2 or 3 feet to see if the signal returns. If it does, your fade was not a fade, but was instead a null.
- If the signal does not return, you have a true fade point. Now start phase 3 with the transecting lines grid. Mark (or remember) this fade point, turn 180., and move across the slope to your other fade. This is your first bracket; move to the mid-point; orient the unit; and do the next bracket perpendicular to the first. A comment about the induction line method: In the past, there has been a reluctance to teach induction line technique to beginners. They could get irretrievably confused and blow the whole search.
- Our experience has been the opposite. The beginners take very quickly to the induction line method. They simply move in the direction of the sound. It's natural. Their instincts, their adrenaline, everything is propelling them toward the sound.
- This is in contrast to the classic grid technique, where everything moves against the novice instinct. You get a strong sound, so you turn it down so you can hardly hear it. Instead of moving toward the sound, you move away from it, looking always for another fade point. The induction line technique is natural; the grid system is not.
- BUT, having said all that, never, never skimp on the classic grid drills. Simply getting close to the victim is not enough; you've got to find her. The induction line method will get you close, but it's the grid that will mark the location. Also, if you get confused, the grid is the only sure way to get unconfused. While the induction line technique is fast, it can frequently lead to confusion. The grid technique is what you need to get bailed out of your problem.
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