 Poster: A snowHead
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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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?
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You need to Login to know who's really who.
You need to Login to know who's really who.
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I have a friend who builds transmitters for radio hams let me know the specs and I'll speak to him but not until the new year as he is in New Zealand at the moment.
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Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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From what I can work out from a bit of googling the transmit specs are just to transmit at 457kHz +/- 100Hz un-modulated. Doesn't sound difficult.
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You'll need to Register first of course.
You'll need to Register first of course.
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Russell - be interested to see what ideas your mate would come up with.
Peter,
I think the transmit spec has a little bit more restriction, but not much more. Like you, I googled and found a spec for testing conformance to the full spec ( testing to ETS 300 718 ), and it looks like the transmit spec is;
unmodulated signal, transmit a 457 kHz signal +/- 100Hz. , A1A. On>= 70ms. Off >=200ms. Period= 0.9s,+/- 0.4s ( on time plus off time ).
Finally, this thing doesn't need to be particularly robust or small. In fact, maybe better if it's not. Would not want some fool to think it could replace a commercially available, critical piece of safety equipment.
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TJon, I had a quick look on Maplin and couldn't find a 457kHz transmitter. There again I didn't look for long. Time also prevented me from finding the extra details you did, well done. Best of luck with finding a cheap TX module, let us know if you succeed.
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Page 29 on this document shows how to build a transmitter http://elmicro.com/files/manuals/drm005.pdf, this will transmit at 433MHz but I think if it was used with the correct crystal frequency it would transmit at 457MHz. You can order samples for free at freescale.com but since it is microcontroller based someone will need to write the code and program it. 
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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.
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Jimbo
tried to check the link you included , but it hangs. I'll try again later.
Just one point tho' - are you confusing Megahertz (MHz) with Kilohertz (kHz)?
The transmitter spec is for 457 KILOherz.
Update: a friend has sketched a circuit that he thinks will do the job. Not built it yet, so don't know how well it works. I will post here when I have any results. In the meantime, all other ideas welcome. Cheers
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
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| TJon wrote: |
Jimbo
tried to check the link you included , but it hangs. I'll try again later.
Just one point tho' - are you confusing Megahertz (MHz) with Kilohertz (kHz)?
The transmitter spec is for 457 KILOherz.
Update: a friend has sketched a circuit that he thinks will do the job. Not built it yet, so don't know how well it works. I will post here when I have any results. In the meantime, all other ideas welcome. Cheers |
Doh, well spotted, but what's three orders of magnitude between friends. 
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Masque -
wow! You found a Uk shop that actually stocks the things!!
Still 60 GBP tho'.... ...so right at the top end of what I would want to spend. I'll keep the link as a backstop, in case the DIY solution doesn't work.
Can anyone out there do better than 60 GBP for a transmitter?
TJ
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You know it makes sense.
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Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
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TJon's opening comment leads me to ask if there are any groups who get together to practice avalanche beacon searches in S.E. England? I know that it sounds very anorak-ey but I could use some practice doing searches with the transceiver. The information on sources of the Nic Impex, Pieps and Ortovox transmitters has been very useful - thanks to all who posted information
Marmotte farcie
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Poster: A snowHead
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In passing I hear that the Ski Club of GB have this year retired all their old analogue Autophons from their hire scheme pool. So there should be several hundred going for peanuts. Give them a call!
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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There is a very helpful .pdf document on the design and use of transcievers at:
Avalanche transcievers technical details
It is interesting to note that the makers of the transcievers still all have their own pulse rate and mark/space timing of their signals. In fact Ascom used to make a test transmitter with about 8 different transmitter simulations, for use in training. I can't find any details on the web, but I remember there being a chart of these on a web page I found one day..
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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?
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TJon, I'm an avalanche instructor with the National Ski Patrol here in the States. This is the "dry" practice that I use with my students even when there is snow cover. Buy a package of fifty or more lunch bags put a few pebbles or small stones in each bag. Place the bags in any pattern twenty or thirty meters across with the extra transceiver in one of the bags. Time how quickly you can locate the hidden transceiver. This is much more difficult than it appears. When you stary to get good use even more bags and increase the size of the search area. When and if you have enough snow cover and can locate the correct bag quckly try this. Bury a wet suit at depth locate the area a close and quickly as possible and use a prob to locate the wet suit. Its quite real.
Bottom line is don't practice by hidding your beacon in the leaves when you can use the paper bags. You can get many reuses of the bags. Great practice.
Bon Ski
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You need to Login to know who's really who.
You need to Login to know who's really who.
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Colinmcc and Jean Claude Mogul
Thanks for the excellent ideas!
The lunch bags one sounds really neat.
I still haven't got round to building the transmitter my mate sketched yet.
In the meantime, I'm off to a local park tomorrow with a mate to do some practice the traditional way.
I'll report back here embittered and twisted if any of the local kids nick the transceiver 
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Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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Result ! Ski Club of GB were happy to flog me one of their old analogue transceivers that was due for retirement. Thanks for the suggestion, Colin.
Prior to that, a mate and I headed off to the local London park with our (digital, BCA Tracker ) transceivers to do some practice.
A couple of hours mucking around with them in the cold but flat terrain gave us both a lot more confidence in using them. OK, so you don't get the hassle factor of trudging up hill thru cruddy snow, but you are able to drill the basic searches. So, we're much faster at the phase 1 and 2 searching now.
And we had a laugh finding some of the numb-nut mistakes you can make. For your edification, here's some "tips" and "gotchas";
(a) drink a few beers beforehand, to reproduce the "trauma" and dumb thinking of an emergency situation 
(b) ignore all the normal people staring at you as do the practice. Just accept you look a t**t
(c) in woodland, the search path as you follow the signal will take you thru all the narliest thorn bushes and nettles in the area. Guaranteed.
(d) our BCA Trackers have a safety feature which can switch them back to transmit-mode after 10 minutes of searching. If you forget that this feature is on, and are taking *ages* on the search, then you can be surprised when the display suddenly goes blank. We thought the batteries had run out ... ...doh! ( then again, if it's taken you ten minutes to get near the victim, they're probably screwed anyway )
(e) and, finally, when you've had enough, I recommend hiding the "victim" transceiver in the branches of a tree rather than under leaves on the ground.... ..but don't tell your mate. LOL - watching him spend ages bitching about lost transceivers and not noticing the bright orange plastic bag suspended above his head. Of course, I explained this was all about simulating deep burials, and nothing at all to do with taking the mick...
About the only mistake we *didn't* make was hiding a "victim" transceiver without switching it on beforehand.
All in all, a very useful exercise.
And the beers afterwards tasted marvellous!
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You'll need to Register first of course.
You'll need to Register first of course.
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TJon - who was the contact person at the Ski club who sold you the old analogue transceiver mentioned in your last post?
I had a very quick look on their site without result and I would like to purchase an old transceiver to use for practice if they've still got any left.
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TJon, Ditto marmotte farcie's,post.
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marmotte farcie, Bernard Condon,
- spoke with the lady at the SkiClub. Nice, positive reply;
"Thank you for your query regarding posting info about transceivers for sale on Snowheads. It would be great if you could suggest people either email info@skiclub.co.uk or telephone the Information Department on 0845 45 807 83. Thank you for consulting me on this, I appreciate it. It will be great if people can make some use of them, since they are presently redundant."
Bear in mind these are analogue Barryvox transceivers, so pay attention to the caveats.
Have fun !
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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.
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Many thanks to TJon - I contacted the ' lady at SCGB' and she sold me two of the old Barryvox transceivers which I can use to simulate multiple burials for some much needed practice (I hope that I never have to use my transceiver in reality).
Thanks again for the information - this is a superb forum with so many knowledgeable contributors who are prepared to share their information, experience and advice.
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TJon,
Glad that they were helpful! May I ask what the 'Club charged?
I still carry one, a VS68, in a ziplock bag in my pack for use in training. I have several left over from the past and now when seting up a training exercise have no moral problem with just turning one on onto transmit and flinging it out into a slope. They are so bombproof that after 18 years (the oldest, bought in Davos in the 80's) I have still to break one. (or lose one) 
Actually, they are still available, now in a very updated form called the VS2000, the web site in English is here at:
http://www.barryvox.com/productfamily/girsberger/index_e.html
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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colinmcc,
The ones I got from the SCGB were Barryvox VS68's and cost £20 or £25 each (I haven't yet seen the credit card statement and I don't recall whether I got them a bit cheaper because I asked for two)
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And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
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I got the same price as "marmotte". As a side-benefit, my girlfriend wore the old styleeeeee analog barryvox during last week's holiday. Made me happier to take her off the groomed runs and seemed to give her more confidence too.
Yeah, I know, ideally, she should have had a shovel and probe too!
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TJon, 'Yeah, I know, ideally, she should have had a shovel and probe too!' - Who is going to dig YOU out then ?
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You know it makes sense.
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TJon,
Glad the KGB came through! 
Finally found my notes, made on a canadian Avalanche Course some years ago (from a Barryvox tech doc I think) describing the mark/space ratios of different brands of transcievers.
I still haven't a clue why it isn't part of the 'standard'... Ie why don't they all use the same on/off ratio? As a simple soul I'd think that the longer they transmitted for, the more time those receiving would have to pick up and lock onto the transmitter... Any techies out there got any thoughts?
On/Off 100ms/880ms Mammut Barryvox. Pieps.
On/Off 320/660 Barryvox VS2000, VS68
On/Off 200/780 ?
On/Off 100/580 Ortovox M2
On/Off 250/600 Ortovox M1
On/Off 70/850 Arva 457
On/Off 90/700 Tracker
On/Off 300/650 ?
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Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
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JimboS, Ive got a simple transmitter circuit, the real problem as has been mentioned is that there isn't a commercially available 457kHz crystal, well I never found one and I also couldn't find one with and easy divisor to get there either. I'm told crystal manufacturers will make them to whatever frequency you want and there are apparently lots of other ways of getting there but its all well outside my area of expertise - expert help required
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Poster: A snowHead
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Also found this some time back. If you want to build a beacon from scratch there's loads of interesting stuff here AviTrans but I seem to remember there's a problem with the transmitter circuit but can remember what it is.
Edit: Just remembered what the problem is, they couldn't get an oscillator of the right frequency so fudged it and built it to work on a different frequency
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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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?
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| Quote: |
| I seem to remember there's a problem with the transmitter circuit but can remember what it is. |
Yup - the probelem is the antenna design!
Any RF engineers with ideas for an easy solution out there....
(preferably not involving expensive lab equipment!)
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FAQ
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