avalanche rescue

How does an avalanche beacon work

That little box you hide under your outer clothing.

The lights that flash on it when you turn it on.

That piece of survival equipment that you never want to use but could save your life in the event of you being buried in an avalanche.

Ever wondered how does an avalanche beacon work, well this article will give you more information and more confidence in your kit.

Beacon – transceiver – which one is correct.

Your little box of tricks, avalanche beacon should really be called a transceiver as it is capable of performing a dual role.

The main one as a transmitter and a secondary one as a receiver.

Hence the name transceiver a combination of transmitter and receiver.

So the correct terminology is avalanche transceiver.

Calling it a beacon may confuse some people with the other types of distress beacons, working on completely different frequencies and for different purposes.

Battery life

Avalanche transceivers operate mainly on alkaline batteries.

alkaline battery discharge curve
battery discharge curve

The reason for this is their discharge curve ( how the voltage of the battery changes as the battery is used).

With this known, and changing, voltage the transceiver can gauge (ish) the remaining life of the battery and give this indication at switch on of the beacon.

Don’t forget to replace your batteries when it tells you that you have less than 40% capacity remaining.

Lithium and rechargeable batteries have different discharge curves and can confuse your transceiver into thinking there is a lot more left than there really is, which is why they are not recommended in the transceivers.

Don’t be too concerned about switching your transceiver off all beacons must last over 200 hours on one set of batteries, with an additional half hour in receive mode at the end.

200 hours equates to 8.3 days on continuously – so if you are using it for 5 hours a day – you can go for 40 days without replacing your batteries.

So one set of batteries will be good for a season. Just check the remaining capacity at switch on.

Transmitter operation

The frequency of all the modern avalanche transceivers is 457 kHz, so they will all work together.

They are low power transmitters designed to operate for long periods with no problems.

how does an avalanche becon work radiation pattern
over the top of a buried beacon

The transmitting antenna is made of ferrite, with a coil wound around it.

This gives a close in magnetic radiation pattern similar to a magnet, where the radiated pattern looks like an onion or an apple. The core of the apple being the ferrite rod.

The transmitter pulses at about a one second rate, and most manufacturers transmitters are the same.

With the newer digital transceivers they may have two or three antennas and might select between two of them, depending on the transceiver orientation giving you the best chance of being found.

The range of the transmitter is about 50m.

Receiver operation

This is where the major differences are within the transceivers.

There are older types of analogue receiver which rely upon signal strength and the increasing signal strength will increase the volume of the speaker.

Whilst good this type of search method can be slow and you need to listen and constantly wave the transceiver in front of you to determine the change in volume.

The newer digital types of avalanche beacons rely on a digital receiver.

They take the signals from two antennas and combine the signal to give you direction and distance from the buried beacon.

This way you can ‘follow the arrow’ shown on the display to be within the fine search area – the last couple on meters.

This last couple of meters is where you will be relying on the numbers reducing and when over the top they will

avalanche probe
avalanche probe in use

increase and decrease within an arms reach.

This gives you a precise location for the beacon.

Now out with the probe to confirm the casualty location before digging them out.

The different manufacturers have different methods of showing you the direction and distance to the beacon.

Some use an arrow – others leds.

But the main thing to note is that you can find the buried beacon quicker nowadays than when you just had the analogue receivers.

The one thing I will stress is to practice – get yourself on a course or practice with a second beacon at home in the garden.

Really become familiar with the operation, so you don’t have to start looking and decoding what the signals means when you need to find your buddy.

Extra modes

Some of the newer transceivers have extra modes in receive, like multiple burials – for when there is more than one transceiver identified as transmitting.

This could be someone in the search party with a device transmitting or it could be two or more beacons under the snow.

But locating one transceiver and being able to ignore its signal and locate the next strongest buried victim is a useful feature and will speed up finding multiple burials.

Another mode is auto transmit – where the transceiver automatically goes back to transmit after a time period or a period of inactivity.

This is a very useful safety feature in case of a secondary avalanche and you get caught.

If you cannot move then you cannot switch your transceiver from receive to transmit.

If you are not transmitting they cannot find you.

In transmit mode you take more power from the batteries, so they will not last as long as in transmit mode. Always worth having spares.

 Your transceiver

So hopefully this article has given you more confidence in your transceivers operation.

avalanche beacon, probe and shovel
Avalanche rescue trio

And some of the extra features you might be looking for in an avalanche transceiver.

Carrying a beacon, probe and shovel is not an excuse to be able to travel into the backcountry without any training.

You really need to know what to do if the worst happens, or even better know where the worst can happen and stay out of the area.

So seriously, get trained and learn how to use your transceiver as a tool.

get yourself trained in avalanche school
Get yourself trained

Knowing that you can find someone with a transceiver set to receive mode is not good enough – you need to have the confidence that you have the ability to quickly rescue your buddies and your buddies can rescue you.

So you have more understanding of How an avalanche beacon works and when you next wear it

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