Avalanche Awareness - It's no joke......

Nagrjuna wrote:
Personally I don't need an exhuastive study to prove the extent of inteference between each model of mobile and each model of beacon - its a lot safer to simply switch the mobile off when you leave the piste - who wants to field phonecalls while skiing powder anyway?

I purposely avoided quoting some lengthy technical information as there seems to be a problem that it's misunderstood, misquoted or quoted out of context. That said, if you read what you actually copied from PH in it's entirety you'll see it says what I pointed out, ie there is no evidence that the proximity of a mobile phone to a victims transceiver has any effect on the searchers device.

Current thinking suggests for search protocols we should attempt to turn off any extra devices in the vicinity.

Nagrjuna wrote:If you have a mobile and beacon that are both on at the same time the mobile interferes with the flux lines the beacon sends out and makes pinpointing you almost impossible.

That statement (above) is wrong while this statement (below) is entirely correct :

ise wrote:
Actually, there's no evidence that a victim's mobile phone interferes with a searchers transceiver.

And to reiterate, if you have a mobile phone on it will not stop you being located by a searcher.

Last words to Bernard GIRAUDON, who you already quoted saying just that :

It is important to note that a transmitting beacon is unaffected so a mobile phone on a victim should not cause any problems.

Thanks, but me, and anyone I ski with will be turning their phones off each and every time before heading off piste. As I said - turning your phone off simply removes any possibility off interference - it costs nothing and removes a degree of uncertainty however slight it may be. Additonally when time is at an absolute premium in a rescue situation fishing a phone out your pocket, fumbling for the off switch in gloves and turning it off (providing you actually remember to do so under duress) before starting the primary search is an unnecassary, time consuming task that wastes someones breathing time under the snow!

If you've been turning your phones off to stop them interfering with the transmit mode that was a misunderstanding, if you wish to carry on doing so as a precaution against a non-existent risk that seems fairly pointless. Precautions taken against risks that don't exist don't add safety while lack of understanding about the equipment we're carrying clearly does diminish group safety.

By all means advise people not to have mobile phones on but if you do then you need to make it clear carrying a phone won't impact them being found in a search.

My background leads me to advise there's no reason to turn off your mobile phone while skiing and a couple of good reasons to leave it on.

I did a test down at the beach a few years back with a digital beacon buried alongside a mobile phone that had no coverage and hadn't aquired a signal. It was impossible to pin down the exact location of the beacon buried with the mobile in the final search as accurately as a beacon buried on its own. It simply wasn't producing the same kind of spike pattern you'd normally expect - if you got that effect in a real life situtation it would lead to having to probe a larger area.

Two things to bear in mind are that ANY source of magnetism/electromagnetism interacts with and diverts the flux lines of a second source of electromagnetic radiation closeby - including the radio waves a beacon puts out. A good way to demonstrate this is to stick a piece of paper to a magnet and sprinkle iron filings on it - you'll get a flux line pattern on the paper - then bring the magnet and paper close to a set of speakers (that have another magnet in them) - you'll clearly see the flux pattern of the original magnet diverted by the effect of the second magnet. This is exactly what can potentiall happen with a mobile near a beacon.

Secondly, the antennae in a beacon are made of ferric material - putting the antennae in a stronger electromagnetic field effects their propeties as transmitting antennae. The ferrile antennae of a beacon are calibrated to work in the electromagnetic field produced by the unit they are part of - change the strength of the field they operate in my factoring in a second source of electromagnetism and its theoretically possible to reduce their effective range. Admittedly this second mechanism is unlikely to have any serious impact - to me its the first mechanism that is the worry.

Theoretically there are clear mechanisms by which a second source of electromagnetism alongside a beacon can negatively effect the ability to find a victim's transmitting beacon. In practice I've seen this effect to some extent and therefore advise people turn their phones off.

A point to note is that modern mobiles only really produce really significant levels of electromagnetism when they can't find the nearest cell antenna and are searching for a signal (something that is far more likely when skiing off piste). As long as you can guarantee you'll be skiing in an area where you mobile gets a signal and won't be searching for the nearest cell you probably won't see any impact on the ability to locate a victims beacon. But in an instance where you're off piste and your mobile is sending out a high strength search signal - there may well be problems.

For me it simply makes sense to remove any additional sources of electromagnetism that have potential for complicating a beacon search. I'm sure everyone has heard the interference from a mobile on a stereo system when it updates with the local cell or recieves a text message - imagine that kind of interference continually confusing a beacon search while a victim's mobile searches for the nearest cell during a search in an area with no network coverage.

Nagrjuna wrote:I did a test down at the beach a few years back with a digital beacon buried alongside a mobile phone that had no coverage and hadn't aquired a signal. It was impossible to pin down the exact location of the beacon buried with the mobile in the final search as accurately as a beacon buried on its own. It simply wasn't producing the same kind of spike pattern you'd normally expect - if you got that effect in a real life situtation it would lead to having to probe a larger area.

A lot of people managed to perform similar tests and get just the same result, it's a classic heuristic trap knowing the result the experiment always proves the hypothesis. I've performed many searches with mobiles on my person or near the sending transceiver and there's simply no effect. The one single time I've seen a signal deflect was from a power line.

As the manufacturers have tried to point out, a phone doesn't effect a victims transceiver. It's a shame people are being confused unnecessarily when others just try to out-knarly each other.

I propose that the title of this thread should be changed to ''Avalanche Awareness - It's 'snow' joke......''

RossF wrote:I propose that the title of this thread should be changed to ''Avalanche Awareness - It's 'snow' joke......''

Are you back yet RossF? Dont forget the pics :lol:

Having just picked up a signal in East Sussex that my M2 reckons is about 35 metres away... I'm inclined to err on the side of caution and switch my phone off (I mean when in the mountains, not right now... 8) ...even though there is currently almost a centimetre of snow on the car), and always have done.

A straw poll of the manufacturers does yield the following...

From the Ortovox M2 Manual :-

Transmitting and receiving performance can be interferred by .... mobile phones and headlamps with voltage regulators. When in use, we recommend switching off mobile phones and walkie-talkies.

From the Barryvox Manual :-

Avoid in general that there are electronic devices (i.e. cellular phones) or metal parts (i.e. pocket knife) in close proximity to a
transceiver which is turned on.

From the ARVA Evolution Manual :-

During a search or a control, be sure to stay away from any electrical equipment (power line, radio, telephone portable) or a radio silence.

From the Pieps Freeride Manual :-

Ensure that, during search, there are no electronic devices (e.g. mobile phones, radio equipment etc.) or massive metal items in the immediate vicinity.

That's not exhaustive, of course, but those models together must cover a significant number of the transceivers in use.

Given that a lot of modern smart-phones now use Wifi as well as mobile spectrum I find it hard to believe that interference can be eliminated completely. I'm open to being convinced but it does appear that the manufacturers feel they're playing safe with the advice above.