Beacons: how they work and what you should know about them.
The basic self-rescue equipment in case of avalanche is composed of shovel, probe and beacon.
The later one is the more complex and it is interesting to know how it works and its peculiarities.Beacons can operate in two different modes, receiving or transmitting a signal by creating an electromagnetic field. By default, devices operate in transmitting mode, allowing the user to be located by their colleagues. Switching to the receiving mode, the rescue team is able to find a transmitting beacon.
There are some important points to consider to choose and to use a beacon:
- We can find analog and digital systems . Digital technology is currently the most widely used because of its simplicity of use. The research is guided by the arrows and numbers showed on the screen. In the case of analog devices, the search is done following the intensity of the signal received.
- The search strip or range (L): corresponding to the maximum distance at which the reception device is able to detect a signal. It should be considered in order to cover the entire avalanche surface during the rescue, no matter if there is only one rescuer or more.
- Beacons use from 1 to 3 antennas that send and receive the electromagnetic signal, provided the approximately 90 ° relative to the other. Nowadays, almost all beacons use 3 antennas that allow a more precise search and a better estimation of the victim’s position. In transmission mode only one antenna is used. Ortovox include (models Zoom, 3 + and S1 +) a system in transmission mode that activates only the closest to the horizontal plane antenna. This system improves the transmitted signal.
In the last phase of the beacon rescue the aim is to locate the exact position of the victim, accuracy problems may arise related to the proper functioning of beacons. These problems are known as spikes and they appear when beacons indicates the position where the electromagnetic field is stronger, which does not correspond to the minimum distance to the buried beacon. Error’s magnitude depends on the depth of the victim and the relative position of two devices (transmitter / receiver). Only devices with 3 antennas are able to reduce spikes.
Practical aspects to consider:
- The battery must always be more than 80% of its maximum load for optimal performance.
- Beacons’ frequency is 457kHz and it must be verified and checked. Control tests can be done in official stores. In any case, group check tests before each use are strongly recommended and can show problems in signal reception. Some models include a specific check test mode to verify the proper signal detection.
- Some models have an automatic self-test is performed each time you turn on the device.
This article is not an equivalent of an avalanche rescue course. Specific proper formation is strongly recommended.
Nacho Olmedo Manich
Jacques Combaz www.flickr.com/photos/jacquescombaz
