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Avalanche transceivers

 Poster: A snowHead
Poster: A snowHead
Gordon,

Where was that from?
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 Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
OwenM wrote:
Gordon,

Where was that from?


Hmm...Switzerland I think.
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 Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
Wow, what a lot of information !

I just wanted to add my thoughts to those of the first few posters. I am a professional avalanche trainer offering courses throughout the winter in Chamonix. I have used a lot of transceivers over the years, and I fully agree that digital is the way to go. Analogue works well in very experienced hands, but most users simply aren't that experienced. I usually compare them as being like automatic and manual cars - automatic might not have the same acceleration, but it is quicker and easier for 95% of people !

Over the past few years I have switched training people on Mammut Pulse to using Ortovox 3+. This unit gets the balance right between ease of use and price. It is just so user friendly I really do think it is hard to beat. I have bought 9 for training clients with. Trust me, when I spend that amount of cash on kit I want to be sure that I am getting the right stuff.

There are plenty of other great transceivers on the market. BCA trackers are popular, and work well, but they are pretty bulky when worn, and I just prefer the 3+.

Anyway, in the next few days I hope to have some comparisons of different transceivers on the Resources Section of our website - feel free to have a look anytime for interesting videos, articles etc

http://www.avalancheacademy.com/page.asp?id=resources

Stay safe this winter

Stuart
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 You need to Login to know who's really who.
You need to Login to know who's really who.
Have you checked, changed the batteries yet?
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 Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
Hi Stuart,
Have you experienced any "flutter" with the 3+?
Can you set the time the transceiver waits before it switches back to transmit? I have done a number of avi courses and have never been told to watch out for this happening, I can see how it can cause problems with multiple searchers.
Do you offer more detailed avi courses, I'd like to learn as much as I can?
Cheers
James
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 You'll need to Register first of course.
You'll need to Register first of course.
Serriadh wrote:
JaMMi wrote:
"ok guys, let's set our transceivers up : I'll take 1 ; Dave you're 2, Will you're 3, Adam 4, Sarah you're 5".


If its something someone has to set up themselves, then it can and will go wrong. But that doesn't matter, because embedding a unique code into something is dead easy, and can be done with numbers large enough that accidental duplicates are vanishingly unlikely.

Its the transmitting of that code that's the tricky bit... radio communication protocols can be exceedingly complex when they need to support multiple simultaneous transmitters (go look at the wikipedia page for CDMA if you're feeling keen). Very expensive to develop, expensive to certify, tricky to get everyone to agree on a standard so all beacons are compatible, etc etc. Its hard to see where all the money would come from; avalanche beacons don't seem like big business to me! I'm sure it'll happen, but I wouldn't want to hold my breath waiting for it.


Hmm you sort of raise a good point (well you do - and I'd given up this thread so it's good to see it is moving ahead/growing/improving : pretty cool) but my feeling is that the best way to combat the issues you describe, would be to keep it simple. I can't imagine anyone wanting to ski in a group of more than 10, so let's consider 20. A number of "up to 20" (1 or 2, or 3... Etc) could be coded into the transmission very simply. Most likely with a simple software tweak - but perhaps an extra chip or two might be needed or maybe an extra button [cue big costs from design/Approval costs perspective]... So let's simplify again. What things do we know of that will be part of the original design of a transceiver? Transmission time, transmission spacing, and perhaps more. What's to stop us delaying the transmission by 1/20th a ms, 2/20ths of a ms, or even the same fractions of a second... I.e we tell the transceiver to broadcast it's assigned number, in such a way that other devices can "read" it's number...

It needs some thought, but surely it's a piece of cake to do, and surely there must be a motivating factor for the designers to consider it since they're part driven by the desire to save lives, not just make money. Whoever gets there first will make their money back.

From a protocol/Standard perspective; it doesn't need to be anything close to WCDMA (or other cellular protocols) levels of complexity. No where close. Consider that the users don't pay a network provider to be able to use the Ava devices, nor will they move between cell sites - requiring handovers - nor is the volume and complexity of the data being transmitted a) as complex [voice or data is prett hard to understand if the quality isn't ensured by the Standard, and tested too] b) as large in size c) private [cellular calls aren't open to receive like Ava transmissions] - the list goes on and on.

It wouldn't/shouldn't be hard to create a paper for whoever governs the RF Standard that relates to these devices, recommending this extra data be considered. Manufacturers and industry would be consulted and they identify the feasibility pretty quickly I'm sure. It's pretty easy to do for cellphones to be honest, except the manufacturers are already pushing all the time for the latest advancements to be included, so they can all offer the next big thing.

If anyone has product design experience (either in electronics or similar, so giving you familiarity with schematics and PCB layout changes arising from such a design improvement, and/or chip design or component change cost awareness, or basic software design knowledge that might help code a solution...) and would consider putting in some time on working on a solution here - please get in touch. My boss may be able to help assess the Regulatory impact, and used to be on the FCC writing commission so may be able to guide well on how to make something like this incorporated into the international standards...

First step (and one I don't think I'd have time to help with; best for someone who does it day-to-day) is having a hardware/software solution with low impact to the manufacturer, which could cater to 20 preset numbers... In my view at least! 'Anyone interested? Smile
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 Then you can post your own questions or snow reports...
Then you can post your own questions or snow reports...
Problem is that all transceivers are wireless transmitting devices and therefore have to conform to international standards - in this case ETSI EN 300 718:

http://www.etsi.org/WebSite/Technologies/AvalancheBeacons.aspx

This mandates that:
* the carrier is 457kHz +- 80Hz
* the modulation type is A1A (commonly known as CW)
* the carrier on period is >= 70mS
* the carrier off period is >= 400mS
* the pulse repetition period is 1000mS +- 300mS

Within these constraints you might possibly encode a unique ID by varying the pulse repetition period but it would be a slow way of doing it. Also, it would mess up those existing transceivers that handle multiple burials by masking at a certain pulse rate - and, for that matter, confuse the brains of searchers using an old analogue beacon.

In any case, there already is a solution - W-Link from Mammut/Barryvox. This was also adopted later by Arva for their Link beacon. This transmits data on a second frequency - 869MHz in Europe and 916-926MHz in the US. Some licence free bands are different in different jurisdictions. These high frequencies have the disadvantage of not penetrating snow well but I assume that the Pulse uses 457kHz for initial location.

I recently received my Ortovox M2 back from repair and took it (an two others) out to the local park for testing. I set up one of the beacons on a table at waist height then, with one of the others, walked away to see how far I could detect it. I repeated this sevral times with different combinations of beacons. Results were as follows:

Code:

Receiver -> Ortovox          Arva              Barryvox

Transmitter

Barryvox    100p (75p arrow) 50p (40p digital) x

Arva        100p (75p arrow) x                 45p (35p digital)

Ortovox     x                50p (40p digital) 45p (35p digital)

The Ortovox is an old semi-analogue M2, the Arva is an ADvanced and the Barryvox is an Opto3000. 'p' means paces.

The range of the M2 is so much superior to the digital models that I'll be sticking with that thanks - despite what others think. It was also a good exercise for getting a feel for what these distances look like in real life. Much easier than clomping about in the snow in ski boots.

I also found for £1.99 in a local charity shop a Bosieboo Child Out of Range device. You clip a transmitter to a child and the receiver bleats when the signal is too weak. I don't know for sure but I guess this'll use 869MHz (possibly 433MHz or even 2.4GHz). With the same setup this had a range of 80 paces.

Oh yes, and in real life I am an electronic engineer specializing in comms - although not RF.


Last edited by Then you can post your own questions or snow reports... on Thu 5-01-12 12:11; edited 5 times in total
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 After all it is free Go on u know u want to!
After all it is free Go on u know u want to!
Haggis_Trap, Zero-G, My perception is/was that to an extent, that many practice sessions, especially the invaluable informal warm-ups focus more on the individual's ability to use the tranceiver - this leads to potentail crowding of trannys/users which should not be replicated in a real-life incident. Am I being too simplistic/optimistic?

Secondly - Some of the tranceivers operate on an analogue signal, switching to the more sensitive/finely tuned mode when "in range" ala Pulse Barryvox which is what I use.
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 You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
altis, The difference in range between old analogue transceivers and the latest digital transceivers (Pulse, S1, 3+, etc.) is much less important than it was with the first generation digital units (BCA Tracker, Barryvox/Mammut Opto 300, etc.).

That side, the M2 always had a pretty exceptional range, probably due to it's long/thin shape which meant there was space for a longer antenna than any other transceiver.
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 Ski the Net with snowHeads
Ski the Net with snowHeads
Sorry to "thread necromance" (my other car's a carpet and I live in a lamp) but I just saw a video which shows the weakness of signal masking, and/or how difficult multiple beacon readings can be ; worth a look


http://youtube.com/v/y2fcNh3sLFA&feature=youtube_gdata_player

How the BCA Tracker 2 works is here, and I think it's a pretty solid approach ;


http://youtube.com/v/csP5iTkOSq4&feature=youtube_gdata_player
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