Cave radio

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Cave radio

Postby pebblepoint » Mar 7, 2006 9:29 pm

Has anyone produced a reasonably priced, tough, commercially available cave radio that a semi-intelligent person can use?
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Postby Biggimo1 » Mar 7, 2006 10:46 pm

Good question Don. I am also very interested in buying or trying to make one myself.

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Re: Cave radio

Postby NZcaver » Mar 8, 2006 3:50 am

pebblepoint wrote:Has anyone produced a reasonably priced, tough, commercially available cave radio that a semi-intelligent person can use?

Good luck finding one that fits THAT criteria! :youwish:

I'm not aware of any that are commercially available in the US. I think the UK ones and possibly the French ones may be semi-commercially available (like sold to rescue teams). But they operate on a frequency of 87 kHz, which may not be legal to use in the US - it could interfere with the LORAN navigation system. I haven't delved into that issue too deeply as yet...

If you weren't aware, most true cave radios transmit on the Very Low Frequency (VLF) band - somewhere between 30 and 300 kHz. Communication is usually achieved by the magnetic induction effect within the first wavelength of the antenna, rather than by Radio Frequency (RF) emissions like a regular radio. A major downside of using VLF is the very high level of natural atmospheric noise at those frequencies. In my experience if both (or all) radios are located well below ground inside the cave, communication will usually be more efficient (higher signal-to-noise ratio).

I'm not sure how semi-intelligent you want to be, but there are designs out there that you can use to build your own radio. Assuming it's a voice transceiver, any semi-intelligent individual with a bit of training or practice should be able to use it. (Depending on the exact frequencies used, a licensed operator may be required - or not.)

I've also found that common CB handhelds (with modified antennas that I built myself) are surprisingly effective in some shallow caves like lava tubes. But they're probably not what you're looking for. Here's a few links that might help you out -

A US cave radio design courtesy of Brian: (beware of pop-ups) http://radiolocation.tripod.com/Transve ... erter.html

The UK Heyphone cave radio: http://caves.org.uk/radio/heyphone/

The French System Nicola cave radio: http://naylorgr.perso.cegetel.net/cave_ ... A_Mk2.html

A page of cave radio links from the UK Cave Radio and Electronics Group: http://www.caves.org.uk/radio/selectedrefs.html

Good luck! :grin:
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Postby George Dasher » Mar 8, 2006 10:38 am

There are some homemade cave radios out there, but I think NZcaver is correct: there are legal problems in the US because of LORAN.
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Postby Teresa » Mar 8, 2006 12:11 pm

Brian B:
Your very own grotto member, Mike Roos, built one before he passed away. This radio is still in use and is being improved as I write this ( I can verify that it use voice communication thru rock,not just Morse or beeps)--in the St. Louis area. There is a second cave radio in St. Louis which several cavers worked on about 10 years ago,and which operates very well though it has some design issues (caveproof and rigid, but hard to pack).

I don't know which frequencies the local radios operate on; there are other freq available other than LORAN, and the low power of amateur equipment (LORAN = 100-4000Kw) and lack of proximity to sea navigation are reasons cave radio can easily fly beneath the radar screen here. Yes, I know some air-nav uses LORAN-- LORAN may be on the way out in favor of GPS based navigation.

It may still be some time before the non-electronically inclined can build these radios, but they are really easy to operate. Even a girl can do it.
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Postby Jep » Mar 8, 2006 12:12 pm

I have researched the use of the European radios for use here in the States. My FCC attorney stated that the frequency that they use is not permitted for the same use here in the US without a waiver of the FCC rules. As it costs money to hire an attorney to prepare the necessay waiver and filings (this one is not an easy application), we are still only discussing the issue. Besides the waiver for the use of the frequency, we would have to get equipment type acceptance for the radios.

The real Catch 22 of the matter is that if someone already had one of these radios here in the country, the FCC would never be able to detect its usage due to the Earth's attenuation of the radio signal. I cannot recommend that anyone break FCC law, but I do not see how they would ever be detected to be found out.

Think about how great it would be to communicate top-side in a rescue without having to string wire into the cave.

Jep.
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Postby Teresa » Mar 8, 2006 1:49 pm

An interesting side note: with the application of such radios on mine rescue, and the pressure on MSHA and Congress to 'do something' to ensure miner safety, perhaps there may be some movement on this issue.
Many mines still use really, really old communications equipment and techniques.
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Postby Sean Ryan » Mar 8, 2006 2:02 pm

The few times I've seen anyone use radios in caves - for mock cave rescues - they were Army surplus with wire physically run from the outside all the way to the patient. You plug the ends of the wire into the big clunky phone unit, pump it a few times to generate enough electricity to send your signal, talk, and hope you hear something back. These being mocks, the patient's never too far inside the cave, and even with just a few hundred feet of wire unspooled, it's real hard to hear anything.

An upside is that anyone unfaimilar with the cave can follow the wire right to the patient like a trail of bread crumbs. In my very limited experience, that's a more useful feature than the actual communication it (theoretically) delivers.
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Postby Tim White » Mar 8, 2006 2:17 pm

Sean Ryan wrote:The few times I've seen anyone use radios in caves - for mock cave rescues - they were Army surplus with wire physically run...


Those are actually field phones not radios. :big grin:
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Postby NZcaver » Mar 8, 2006 4:20 pm

Sean Ryan wrote:...even with just a few hundred feet of wire unspooled, it's real hard to hear anything.

An upside is that anyone unfaimilar with the cave can follow the wire right to the patient like a trail of bread crumbs. In my very limited experience, that's a more useful feature than the actual communication it (theoretically) delivers.

Yes, the "breadcrumb" effect of the phone wire leading to the patient during a rescue can be very helpful. However, I disagree that's it's "more useful" than the communication it delivers. In my experience if you've been trained how to install and maintain a field telephone link (like the NCRC teaches), and you're using the right equipment in good working condition, you should have yourself a reliable in-cave communication system.

FYI - using the standard WD-1A/TT 2-conductor, copper/steel stranded, army wire (the black stuff), those old crank phones (model TA-312/PT) should have a range of at least 14 miles under damp (cave) conditions. However the smaller sound-powered TA-1/PT handsets have a much shorter range (about 1 to 5 miles), and this is further reduced when more than 2 phones are attached to the line.

And anyway (as Tim mentioned) those are definitely field phones, not cave radios... :big grin:
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Postby NZcaver » Mar 8, 2006 4:44 pm

Teresa wrote:An interesting side note: with the application of such radios on mine rescue, and the pressure on MSHA and Congress to 'do something' to ensure miner safety, perhaps there may be some movement on this issue.
Many mines still use really, really old communications equipment and techniques.

There is already "movement" on this issue - it just takes time, that's all. Work has been in progress for a while, long before the recent mine tragedies. Besides cave/mine rescue applications, there is also some interest in this technology by other government agencies. Eventually the day may come when we cavers can buy government surplus cave radios, instead of just the old field phones and wire. (Don't hold your breath - it could be a while...) :wink:

And yes, there's quite a number of home built cave radio units in private hands around the US. But out of respect for privacy, I'd rather not name any names in this open forum. Some of the links I provided earlier have email addresses listed on the sites, though...
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Re: Cave radio

Postby ian mckenzie » Mar 8, 2006 9:58 pm

pebblepoint wrote:Has anyone produced a reasonably priced, tough, commercially available cave radio that a semi-intelligent person can use?
The Alberta Speleological Society developed a cave radio in 1980 which, along with improvements, was sold to whomever wanted a pair (several in the USA, I believe). Ian Drummond was the designer/producer, but he now lives in Ontario and I'm not sure he makes them anymore. I can ask him if he'd give you the plans to make one yourself, if you're interested.
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Postby Mark620 » Mar 8, 2006 9:59 pm

What about using the same frequency as the radio location equipment? 3496Hz?
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Postby NICKSCAVE » Mar 9, 2006 8:52 am

looking for a cave radio, the book caves of the organ cave plateau. has 2 very nice diagrams provided by RAY COLE on how to build a very stable and cheap radio made from parts available at your nearest radio shack. I have not built one but it looks very simple. A person could probably get a copy of that book from spelo-books or I think also inner mountain outfitters has copies available, minus the organ cave map packet. If you have no luck finding the book, mail me as i think i have some copies of the radio schematic. Hope this helps :waving:
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Postby George Dasher » Mar 9, 2006 10:24 am

WVASS or the NSS would be the best place to try to obtain the Organ Cave book.

Probably WVASS, because I'm pretty sure that it is out of print.

It contains no map packet, as all the maps are included as quads. It was quite ground breaking for that reason.
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