*** Cave Rescue Communications *** Tue Jan 23 07:52:07 1996 Letter : 8896158 From: Douglas Moore Address : douglas.moore@svis.org Subject : Underground Communication -> For those of you involved in Cave or Mines Rescue, what are you using -> for comms underground and how does it perform? We generally use the old reliable field phone. Common ones used in the Eastern Region - NCRC are TA-1 (Sound powered), TA-43, and TA-312. These handle the underground comm. When it exits the cave it may travel directly to the com center or be patched into there via phone or radio. -> We are keen to upgrade soon, probably to something like a Michiephone -> (single wire earth return). Big problem if the wire breaks. With the double wire and standard field phones and earth return can be constructed by doubling the two wires into one side of the phone and connecting the other to a short piece of buried wire. -> I have heard stories about VLF radio being used undeground, but I'm a -> bit sceptical (and I'm not a radio tech to know any better!) Costs and availability limit its access. Some of the only ones used are in use by mine rescue teams. # Internet: douglas.moore@svis.org (Douglas Moore) -> It works - I've been doing a lot of reading in this area. They use -> the magnetic field instead of the electric field, and go through rock -> like it wasn't there. Also has extremely good directional -> properties; if one can believe the literature (and I intend to try -> it) you can pretty well pinpoint the location of the (underground) -> transmitter wrt the receiver on the surface. Pin pointing location is about the only thing it is used for by cavers in the US. It does have sub meter accuracy if properly used. A lot of cavers use them to locate on the surface where to drill so that a better access to a cave can be made. ---------------------------------------------------------------------------- | /\+/\ Douglas L Moore II /\+/\ | | National Speleological Society - 33064SU | | National Association for Search & Rescue - 9501923 | | Staff - Eastern Region National Cave Rescue Commission | | Owner - Karst Sports (Caving, Climbing, & Rescue equipment) 304.592.2600 | | On the World Wide Web at http://svis.org/msc/karst.htm | ---------------------------------------------------------------------------- # Internet: douglas.moore@svis.org (Douglas Moore) Date: Tue, 07 Oct 1997 00:18:35 +0200 From: Roy van Schoor To: sar-l-d@islandnet.com Subject: Re: Comms in Caves >The best thing that we have found for >internal communications is the military field telephones using a very >tough 2 conductor wire. This requires a lot of work on the part of the >commo teams but it is the only thing that seems to be practical. We have >on some rescue put as much as 5,000 feet of wire out with 8 or 9 phones >on a major rescue so it does work. Spares of everything is also >necessary. This sounds like a very practical approach. The interesting part is going to be locating "very tough 2 conductor wire" without going too thick and therefore too heavy for the team to deploy. As a matter of interest, what is the spec on the wire you are using? >There are some specialized "Cave Radios" but most of them are >just for surveying and are not suitable for voice contact. There was a >unit from Great Britian called a "Mole Phone" which did transmit voice >fairly well, but at $ 3000 at pair (in 1987 !!) was a little costly ! >David Tate wrote: >Have you tried going lower in frequency? The US military uses Extremely >Low Frequencies to talk to submarines under water. I don't think that >would be applicable for us but maybe some of the ham frequencies could be >used to experiment with. >Sean Smith wrote: >Roy I've done some work here in western Canada useing radios on >37kHz. We were basing or com. systems on work done by the Cave >Rescue Organisation. The ultra low frequency approach is also used here in the mines, but I believe that the units are extremely expensive. >Tom Q Smith wrote: >I've not tried radio communications in caves, but knowing a little about >how radio waves travel, I suspect the higher frequencies may travel >through the passages, somewhat like microwave moving through a waveguide. >I'll ask some of my associates who hang out in underground places. >Ed Nicholas also wrote: >Your best bet is not to rely on radios for inside communications in a >Cave Rescue senario. There are times that the cave passages can act as a >giant "wave guide" and let the messages go thru, but these incidents are >too few to be dependable. They can be used in pit rescue (sometimes) >from top to bottom but sometimes even this takes a little work to >position the antennas correctly. I think the problem with the waveguide theory is that the internal surface of the average cave does not resemble that of a nice clean metal waveguide! High frequency (VHF & UHF) radio waves tend to be absorbed by the internal surfaces of the cave wall which can be quite convoluted. Thank you all for the ideas, Regards Roy van Schoor Principal Officer: OFF-ROAD RESCUE UNIT * Western Cape, South Africa * Date: Mon, 06 Oct 1997 19:59:45 -0500 From: Ed Nicholas To: sar-l@islandnet.com Subject: Re: Comms in Caves/wire type Roy: The wire we use is USA military WD-1 military field telephone wire. It is a two strand twisted pair with a tough jacket and a combination steel & copper core which makes it almost impossible to cut with a pocket knife !(Without doing some major damage to your fingers if not carefull !!) If you can find the phones the wire should also available. We have found the mile spools (5600 feet or so) for about $75 or so here in the states. This can be cut down and respooled onto 750foot spools or so to make it easier to handle.It is about the toughest lightest stuff we have found. As far as any of the "cave radios" (VLF) stuff goes, my opinion , based on about 10 years or so in this business and 20 odd years of caving is to save your money on radio purchases and scrounge up some field phones. The VLF stuff does have some application for surveying in caves (location of interior spots on the surface) but not much for rescue communications. Again, the molephones are nice when they are available and work, but the phones are more reliable(?) and affordable. Best Regards, Ed Nicholas, EMT-D Chief of Operations Huntsville Cave Rescue Unit, Inc. Huntsville, Alabama USA Instructor, National Cave Rescue Commission NSS 17921F KD4WNJ Date: Mon, 06 Oct 1997 20:50:04 -0700 From: Rick De Castro To: sar-l@islandnet.com, sar-l-d@islandnet.com Subject: Re: Comms in Caves The military uses what's called WD-1/TT wire. It's got three steel strands and four copper strands (I think that's the combo), and comes in spools from 1/4 mile to very long (over several miles, iirc). The 1/4 mile spools are very handy, but the mile spools are very, very heavy (around 90 lbs). The wire itself is very strong, it's designed to just be tossed up in trees, run across roads with wheeled or tracked traffic, etc. Splicing it is interesting. After stripping the insulator off, the book says to bend the wire down, then release it. The copper will stay down, the steel springs back up. Then, taking the two ends you wish to splice together, you simply tie them together with a square knot. You attach the two pieces copper conductors with a twist pigtail splice. >>There are some specialized "Cave Radios" but most of them are >>just for surveying and are not suitable for voice contact. There was a >>unit from Great Britian called a "Mole Phone" which did transmit voice >>fairly well, but at $ 3000 at pair (in 1987 !!) was a little costly ! >> >>David Tate wrote: >>Have you tried going lower in frequency? The US military uses >>Extremely Low Frequencies to talk to submarines under water. I don't >>think that would be applicable for us but maybe some of the ham >>frequencies could be used to experiment with. >> >>Sean Smith wrote: >>Roy, I've done some work here in western Canada useing radios on >>37kHz. We were basing or com. systems on work done by the Cave >>Rescue Organisation. >The ultra low frequency approach is also used here in the mines, but I >believe that the units are extremely expensive. > >>Tom Q Smith wrote: I've not tried radio communications in caves, but knowing a little about how radio waves travel, I suspect the higher frequencies may travel through the passages, somewhat like microwave moving through a waveguide. I'll ask some of my associates who hang out in underground places. >>Ed Nicholas also wrote: >>Your best bet is not to rely on radios for inside communications in a >>Cave Rescue senario. There are times that the cave passages can act as a >>giant "wave guide" and let the messages go thru, but these incidents are >>too few to be dependable. They can be used in pit rescue (sometimes) >>from top to bottom but sometimes even this takes a little work to >>position the antennas correctly. > >I think the problem with the waveguide theory is that the internal >surface of the average cave does not resemble that of a nice clean metal >waveguide! High frequency (VHF & UHF) radio waves tend to be absorbed >by the internal surfaces of the cave wall which can be quite convoluted. > >Thank you all for the ideas, >Regards > >Roy van Schoor >Principal Officer: OFF-ROAD RESCUE UNIT >* Western Cape, South Africa * Date: Tue, 07 Oct 97 10:32:59 -0500 From: Lyle Williams To: Search and Rescue Discussion List Subject: Re: Comms in Caves Someone mentioned submarines using Low freqs and because of this, LF may be good for caves. I don't have any practical experience in caves but I an offer a little xmtr input (no pun intended). Subs now a days xmit on feqs down to ELF (30-300 Hz)(as opposed to HF or VHF 3Mhz-300MHz) to do this, the earth bound antenna is about 28 miles long (no exaggeration). I could only guess at the huge power o/p of the xmitters, I would guess in the multiple KWs though, as power is not a concern. In a cave by contrast, as someone stated earlier, antenna size and power are of great concern. I would think that a 3-7 watt handheld in the 70 cm band (440 MHz) could bounce a signal around rather effectively, eventually finding its way out an entrance somewhere, to a local receiver, as opposed to going thru rock with a low freq, high power radio,this would be impractical, for cavers anywho. I have played around with a number of systems. At reasonable (battery operated) power levels, I have seen 1.5kHz systems work, but not reliably. Coiled antennae are used, and the system is really a loosely coupled transformer, rather than a "radio". Large batteries were required, and these only allowed short transmissions. There were also issues with coil alignment. I don't think 3-7 watts at 440MHz would be reliable in a cave. The most reliable underground communications system I have seen is the Michiefone, a ground return intercom system. This uses a single insulated wire strung through the cave. It works well over many kilometres, and the intercom units can be designed to provide hundreds of hours of transmission off a single 9v battery. Best of all, you can build your own units at little cost. Lyle Williams VK1XLW 07OCT97 Date: Tue, 07 Oct 1997 09:05:51 -0500 From: Wayne Morgan To: sar-l@islandnet.com Subject: Re: Comms in Caves Roy van Schoor wrote: >This sounds like a very practical approach. The interesting part is going >to be locating "very tough 2 conductor wire" without going too thick and >therefore too heavy for the team to deploy. As a matter of interest, what >is the spec on the wire you are using? MilSpec commo wire is two-piece steel wire. It can be had relatively inexpensively through military surplus outlets, when available. Wayne Morgan Date: Tue, 7 Oct 1997 10:09:25 -0700 From: "Kern, Mark" To: "'sar-l@islandnet.com'" Subject: RE: Comms in Caves We use a similar phone system, it is one that the military uses. We have been getting the cable for the phone from the military as they are closing down the bases out here. We are getting miles of cable and we are testing how far it will go out and how well it works at a distance... The other option is to cut a wire of radux coax to the multiple of wave length you need (i.e. using 2 meters, you cut the radux to 2 meters times 1000, a 2000 meter cable) then after you make sure the match is ok, you pull the cable along into the cave and have the radio outside the cave. The radios inside the cave will be picked up by the radio outside with the LONG cable, and you have a relay type system. This method is obviously very expensive for 2000 meters of cable. This is the method that some cities use for keeping radio signals in long tunnels. They string cable along the roof of radux and people are able to pick up the bleed from the LONG cable. -------------------------