DVA security system

Whether you are ski touring or off-piste skiing, you need basic safety equipment such as the shovel, probe and dva (avalanche transceiver) formerly known as ARVA (avalanche transceiver). The airbag is growing in popularity and could quickly become basic safety equipment as well. What is an avalanche transceiver? the principle The dva is an... More details
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Whether you are ski touring or off-piste skiing, you need basic safety equipment such as the shovel, probe and dva (avalanche transceiver) formerly known as ARVA (avalanche transceiver). The airbag is growing in popularity and could quickly become basic safety equipment as well.

What is an avalanche transceiver?

  • the principle

The dva is an electronic box that you carry with you. In emission mode, it emits sound signals (frequency 457mhz). In receive mode, it picks up these signals. When you progress on skis, your dva is positioned in transmit mode. If you find yourself buried under an avalanche, the people in the area will put their dva in receive mode to locate the sound signals and locate you. All the dva models available on the market transmit and receive at the same frequency and are therefore compatible with each other.

  • Analog or digital?

Until 1998, manufacturers used analog technology. In this case, the signal of the transmitting DVA is converted by the receiver into sound waves. When a receiving DVA picks up a transmitting DVA, it emits a "beep" that is all the louder the closer the two devices are to each other or the more correctly oriented they are in relation to each other. A potentiometer allows you to vary the sound intensity of the signal by adjusting the sensitivity of the receiver. All DVAs manufactured before 1998 are analogue.

In 1998, a second generation of DVAs appeared, using digital technology exclusively or in combination with analogue technology. This is referred to as digital DVA. The signal from the transmitter is analysed by a microprocessor which converts it into two types of visual indications:
- a progress indication (numerical value appearing on a screen);
- a direction indication (LED or arrow which lights up when the DVA in reception is correctly oriented in relation to the device in transmission).

Is the analogue D.V.A. obsolete today?

The answer is yes! And for different reasons!

The first one is that like a car, a DVA must be checked regularly, in a shop or by its manufacturer (see box at the end) ; however, there is no more maintenance on analog devices. There is no way for the user to know if their DVA is working properly when they start an outing.

The second reason is that "current and future devices no longer take into account the compatibility with analogue DVAs (frequency tolerance, signal shape, etc.)", according to the FFCAM. Even if its analog DVA works perfectly, there is a great risk that modern DVAs will not be able to detect it under the snow.

Third argument, the ease of use of digital DVAswhich is crucial in a panic situation. Even when trained, the rescuer (in the broadest sense of the term) is disturbed by several external factors, such as his or her relationship with the victim or stress. Enough not to add a DVA requiring a level of reflection worthy of a chess player in the final phase of the world championships of the discipline. Even if digital DVAs don't think for you, they are more intuitive to use.

Choosing the right D.V.A.

There is a large choice of DVAs on the market such as the historical Arva brand, the Mammut mountaineering brand or Pieps for mountain safety products. Several manufacturers have invested in the avalanche victim detector market, to the point that the skier does not know what to choose between ease of use, the wealth of functions, or simply the price.

  • First criterion: Ease of use and readability.

This is the unassailable criterion for choosing the DVA, which concerns both first-time buyers and the most experienced skiers. As the Anena points out, shape, size and weight are not criteria.

At the beginning of the ride, the activation of the emission mode must be done in one single operation and must not be confusing. When searching for a victim, switching to receive mode should be done instinctively, by pressing a visible button, for example. The display must clearly show the index of progress towards the victim and the direction in which the victim is moving, without any possible ambiguity.

  • Second criterion: Useful range.
Each manufacturer specifies for its DVA either a useful range or a search bandwidth, expressed in metres. It is not the same thing. The effective range is the ability to receive a signal from a certain distance. For example, if you arrive at the avalanche site and switch to receive mode, you will start receiving a signal at, say, 25 metres from the victim. This is the effective range, which today is no more than 35 meters in recent models.

The search bandwidth is twice the useful range, i.e. a maximum of 70 m: when the rescuer is in the middle of the coulee, he will receive 35 m to the left and 35 m to the right. So be careful not to rely on a data sheet that indicates 60 m of useful range, it is not possible. However, it should be noted that the longer the rescuer has a long range, the less time he will spend looking for the first signal.

On the buried person's side, the transmission power of the signal also depends on the quality of your DVA; unlike the reception aspect, however, the manufacturers do not give any figures, so it is difficult to compare the transmission powers of DVAs with each other.

  • Thethird criterion is the number of antennas.
Knowing the number of antennas in your device is also relevant. The first antenna has the longest reception range, and gives the progression index in meters. It is also used for transmission. The second antenna works with the first and allows the processor to calculate and display the direction to follow. Most models now add a third antenna to locate the victim in 3D, once close to the victim. A DVA without a third antenna can cause "double maximum problems", which are announced at two opposite locations because of the magnetic field lines of force. The victim's true vertical, which is between the two maxima, must be manually searched for.
  • Criterion 4: Diversity of functions.

In addition to the basic capabilities listed above, DVAs carry features to aid search, provided that they are capable of being used. The most obvious is marking: when the DVA picks up multiple signals, it automatically leads to the strongest one. Once the person has been located, it is possible to block the signal to search for another victim.

DVAs sometimes display the fact that they are picking up multiple transmitters from the outset. This information is essential for the professional and can be confusing for the novice. The latest devices are also used as a GPS, with a screen that schematically displays the steps to be taken, from sweeping the avalanche area to snail sounding, or displays a map with the estimated position of the victims. Here again, training in their use before going skiing is essential to avoid finding yourself at the crucial moment with too much information to manage.

Maintain your D.V.A. well

A DVA, like any electronic device, should be stored away from heat and in a dry place. At the end of the season, remember to remove the batteries as the manufacturer's warranty does not cover damage caused by leaking batteries. Also, removing batteries at the end of the season allows you to think about getting new ones to start the new season.
Another useful recommendation: have your device checked by your manufacturer or in a store within 5 years of new purchase, then every two years. These revisions allow manufacturers to recalibrate the antennas but also to check the condition of the housing, battery switch, etc.

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