underground communication

[dhparker]

I've been fascinated with caves since my early grade school years when we took field trips to some of MO's show caves. I've never been in a wild cave. I don't think I've got the guts for it. Anyway, I grew up to a fiction writer, not a caver. Since some of my stories are set in Missouri, though, all those caves memories in my background naturally want to be included.

I'm here because I don't want to put anything inaccurate in my stories, even though they are fiction. So, I hope you won't mind me hanging around and asking some questions. I definitely need help getting the cave parts of the story right.

The most pressing question right now is about underground communication. I'm thinking that walkie-talkies, radios, cell phones, etc. would be useless underground. If two groups of people were in different areas underground (part of one cave system, but separated), is there anyway to communicate?

Thanks in advance for any words of wisdom.

Donna

[Tony Anders]

My experience tells me that you may be able to use some radios , but the radios would be more or less line of sight, or in a cave unobstructed antenna to antenna. From what I have researched in trying to set up for cave rescue the most reliable communication would be wire system of some sort.

caves.org.uk/radio/heyphone/

Something like the link above would work.

You can also look at this link from this forum
nssmembersforum.proboards28.com/index.cgi?board=talk&action=display&thread=1147815442

You can like I said use the FRS radios or regular ham radios. if you was in a straight shot cave no bends or pits, you would probably get several hundred feet. It would be limited to power of the radio and type of rock and battery strength in the radio. You might possibly bounce a radio signal off some walls in the cave and get to communicate around a bend.

This is my opinion from my research and experience with radios.

Radios would be good if you are on a survey team and was using it to keep from yelling out numbers and stuff. but again, you will most likely be within several 100 feet of each other

Hope this helps...

PS, I have also heard of someone placing a yagi type antenna at the cave entrance and using it to relay information from the caver's inside to the world outside, or more then likely the opposite since the stronger transmitter could be placed outside easier than carrying a 50 or 100 watt transmitter inside with you.

I am sure some other more experience caver's in this forum will have much more info on this matter than I do.

Then again if you have the big bucks, you can set something like this up and talk pretty good I would say.
www.sara.com/ISR/low_frequency_EM/magnetic_communication.html

Good question by the way, way to get us thinking....

[saltpeter]

Hello Donna, Welcome to the forum!

One of our forum members, Azurerana lives in Missouri so if you want to go on a wild caving trip she would be a good caver to ask about arranging one.

I am not an expert concerning underground or cave communication but I took the liberty and looked up a few online resources that may assist your research. My understanding is in-cave signals from walkie-talkies, radios, cell phones will not carry far due to the nature of the cave. I may be incorrect (someone do correct me if I am) but those signals need a line-of-sight to transmit properly. As other cavers log on the forum today they should be able to assist you further. We appreciate you trying to avoid inaccurate information in your stories and will help you all we can so do feel free to ask all the questions you need.

Summary of the Cave Rescue Telephone Project by John Halleck
www.cc.utah.edu/~nahaj/cave/phones/

Communications in Caves by David Gibson
www.caves.org.uk/radio/comms_in_caves.html

David Gibson's Cave Radio page
Information on through-rock radio transmission
www.caves.org.uk/radio/

[Azurerana]

Wired field phones work great (getting hard to find). Cell phones--useless--make great light sources, though. Family frequency walkie-talkies-- marginal over a few hundred feet of open passage, but I've seen it done.. Ham radios--nope, unless you've got lots of repeaters underground. (Research coal mine radios w/repeaters for possibilities). A few cave radios (extremely low frequency location devices sometimes used to communicate to the surface) have voice capability. We know of one being used in Missouri where the cave radio is wired into cheap CB radios. Cave radios can be used to signal via on/off Morse code if you happen to have an intermittent switch on the transmitter. That will work through rock if you have a prearranged code, or people who know Morse on both ends.

[Brian Roebuck]

As a ham radio operator I'll add some general stuff to this post. The higher the frequency of a radio the more it tends to propagate signals in a straight line. In other words low frequencies can bend around corners more efficiently. Very low frequencies can actually pass through solids such as rock well enough to do some communicating. Typically these radios are very expensive, massive, and require large power supplies. This makes them impractical for cave use. Rescue teams and expedition teams regularly use wired military phones for light efficient cave communications. They are easy to use and easy to repair and maintain in difficult environments such as caves.

N4YQL

[Tony Anders]

Hey Dr. Beaner
I didn't know you was a ham operator. I am wanting to get me no code tech license as soon as I can get a test location close by. At least attempt the test I mean

[Brian Roebuck]

Tony,
Now is a great time for you to use extra time while you are healing up to study for the no code test! I have a general class license from about 20 years ago and probably have forgotten most of what I studied by now. Still I keep the license and occasionally get on the air. We HAD to do code back then to get any license. It was tough but worth it.

Good luck with your test!

[Tony Anders]

OK, do you know where I can get a copy of that book so I can study?

[Brian Roebuck]

muddog said:

OK, do you know where I can get a copy of that book so I can study?

Try here Tony:
www.arrl.org/

I think they have all that stuff or links to where you can get it.

[Azurerana]

My brothers are WB0MHU (extra class) and N0YZS. Father was KB0OLW until he died.

Grew up in a house where transistors were what you stepped on in the brothers' rooms, the station was in the kitchen, and they'd tap Morse to each other on the kitchen table. Dad was Radioman for 64th Tank Battalion in Korea, 1950-52. Bill had his General Class at age 13. The other two waited until they had the 5 word a minute Tech class-- which both passed easily although Dad could transcribe sent Morse much faster than that, even 30 years out of the Army.

Fr. Paul Wightman, NSS 800-something, called Eugene one day to see if he needed any radio locations at Onondaga Cave. Gene said no, but did he do weddings? As part of the 'gift for the minister' we gave Fr. Paul a statue with little earphones and a receiver coil called "Our Lady of the Cave Radio".
I know a lot about radios in self-defense. Even a little Morse--like my name, the dit letters, the dah letters, some of the other common ones-- you might not believe this, but in the 1960s, the Girl Scouts taught the Jr. GS's Morse Code!

[L Roebuck]

Wow, It is beginning to look like we may need a new topic just for the Ham Radio Operators. ;D
Years ago, I began the study for my Ham Radio License (guilt by association ) but I just never took the test. I know...Baaaaaaaaad Lynn.

BTW Tony I think my book came from Radio Shack so you might check that store out. [Way Off Topic] If you ask sometimes behind the desk they have a handout of all the local Scanner frequencies too.

Are any Ham Operators on the forum participating in any Emergency Rescue Operations?

[NZcaver]

dhparker said:

The most pressing question right now is about underground communication. I'm thinking that walkie-talkies, radios, cell phones, etc. would be useless underground. If two groups of people were in different areas underground (part of one cave system, but separated), is there anyway to communicate?

Thanks in advance for any words of wisdom.

Donna

Hi Donna

As you've probably figured out from the previous replies, caves generally present interesting/frustrating challenges to technical communication.

If your story centers around a cave in Missouri, you are probably talking about a place with fairly high ground conductivity - which is bad for radio. Put another way, if the caves are wet and/or the rock has a high iron content, most radio signals will be too well shielded to be effective.

Very Low Frequency (VLF) transmitters are sometimes used to get around this problem. They work because of a magnetic field effect that allows the signal to penetrate rock quite effectively (I have over-simplified a bit here). However, the units are generally home-made, not all that compact, and are few and far between. If you ever see one in a cave, it's probably being used for radio testing, radio location (relating a point in the cave with a point on the surface), or cave rescue.

Handheld radios are sometimes used by cavers, but are mostly for line-of-sight communication (like from the top to the bottom of a pit). Cheap FRS walkie-talkies are popular for this, and cavers might occasionally use VHF ham (or even CB) handhelds line-of-sight too. You can pretty much assume that a cellphone will be useless in a cave.

Interestingly, if your setting was to be a dry cave in Arizona, parts of California, etc - you can actually get some reasonable range through-the-rock on CB and VHF bands. (The Park Service at Lava Beds, northern California, can actually use their VHF handhelds reliably in many of their lava tubes.) This however, is not the norm for "most" caves in the US (or the world).

As a general rule, when reliable communication is required in a cave you run a phone line. The tough, 2-conductor insulated wire the army use works well, along with the old army field telephones with the crank handles. Installing a cave phone system like this is standard procedure during the early stage of most cave rescues, and is also used as a convenience/safety link in some multi-day, deep-cave expeditions. The army phones and wire, by the way, are not as expensive and hard-to-get in the US as some people make out. The phones are regularly listed on eBay, and the wire can often be found at surplus stores.

Short answer - if your story revolves around "normal" cavers on a "normal" trip, it's highly unlikely they would bother bringing radios or rigging a phone system to talk to each other through the rock. But it *could* be done, justifiably, if you get a little creative with your storytelling. Or you could lose the high-tech approach, and simply have 2 groups separated by an impassable drop (or climb). They can yell back and forth, but cannot directly see or get to each other.

I'm not sure if all this will help you with your research, but good luck anyway!

[dhparker]

Thank you all so much for the kind welcome and all the information! You've been a great help! It is a Missouri cave and it is wet. Now I need to go to the cave rescue forum and start reading there. I don't doubt I'll have more questions in a while.

As to ham radios, both my brothers (they're twins) are hams. W4AW in North Carolina and W4ET in western Kentucky. (If you talk to them, tell them big sister says hi--or whatever radiospeak is for that these days.) I had to dodge radio equipment around the house, too, but that was many years ago. ;D

[madratdan]

Hi Donna,
Welcome to the forum.

As others have stated, the most common phones are the old, WWII style, two wire phones. Surprisingly, most cave rescue groups possess several sets of these phones. For instance, here in Colorado, we have the Colorado Cave Rescue Network. We have two different stashes of equiptment, one in Colorado Springs and one in Glenwood Springs. Both places have several sets of field phones, along with several miles of wire to go with them. The equiptment stash in Colorado Springs alone has 9 hard wire phones.

We also train with the local fire dept., confined spaces rescue unit, who also has three or four hard wire phones along with thousands of feet of wire to conect them together.

[Azurerana]

Hey NZ--

All the cave radio work I've been on (holding the radio equivalent of the dumb end of the tape stuff) (save one) *has* been in Missouri, and they work just fine (as long as the radio antennae aren't broke.)
Why?
Most of the caves aren't that long, nor are they that deep. They also do not tend to be multilevel caves but dendritic ones. The passage curves, and goes out of sight, but there is some signal bounce, because although most of the "dry" caves are muddy stream passage, the rock walls tend to be dry. (Spring caves excluded, of course.)

They've got a cave radio trip going this weekend near Lake of the Ozarks.
best
Azurerana

[NZcaver]

azurerana said:

Hey NZ--

All the cave radio work I've been on (holding the radio equivalent of the dumb end of the tape stuff) (save one) *has* been in Missouri, and they work just fine (as long as the radio antennae aren't broke.)
Why?
Most of the caves aren't that long, nor are they that deep. They also do not tend to be multilevel caves but dendritic ones. The passage curves, and goes out of sight, but there is some signal bounce, because although most of the "dry" caves are muddy stream passage, the rock walls tend to be dry. (Spring caves excluded, of course.)

Hi Az

If you're using so-called "true" cave radios (ie VLF, using mag induction rather than RF), it shouldn't matter that much if the cave is long, deep, wet, etc. I hope my previous post isn't too confusing on this point.

However the closer you are to the surface with VLF, the more problems you can have with high ambient noise (QRN - static from lightning strikes half a world away, etc). Still, even cave radios have a maximum range underground - and this will differ widely from cave to cave, and from karst region to karst region. In some places it's even possible to maintain effective communication through solid rock while 1000 feet or more apart.

It's the regular CB and VHF handhelds that can sometimes benefit from shallow-depth/shorter/drier caves. UHF (FRS) are still only reliable for line-of-sight, in my experience.

(Sorry, I'll stop lecturing now.)

They've got a cave radio trip going this weekend near Lake of the Ozarks.
best
Azurerana

I'm jealous - I haven't been on a cave radio trip in quite a while. In fact, I haven't even been caving for months. Sad.

[NZcaver]

madratdan said:

As others have stated, the most common phones are the old, WWII style, two wire phones. Surprisingly, most cave rescue groups possess several sets of these phones. For instance, here in Colorado, we have the Colorado Cave Rescue Network. We have two different stashes of equiptment, one in Colorado Springs and one in Glenwood Springs. Both places have several sets of field phones, along with several miles of wire to go with them. The equiptment stash in Colorado Springs alone has 9 hard wire phones.

Hi Dan

Question - are you really still using the old WWII vintage EE-8 phones for cave rescue there (like this one)?



In my experience, these can be horribly unreliable. They are not sealed units, and are therefore prone to corrosion - especially with cave water and mud getting inside the workings. They are also infamous for handset cord problems.

The later TA-312 field telephones (first introduced in the 1950's) are more robust, reliable, and slightly more compact. They are now the "standard" most frequently taught by the NCRC (although this may differ region by region).



The much smaller and lighter TA-1 sound-powered phones are also somewhat popular, although they have a much more limited range - especially when more than 2 phones are connected to the same line.



(Sorry, I guess I got carried away with my photo posting there.)

[Edit - I changed the pictures to thumbnails for your viewing pleasure. All pictures are mine, except the EE-8.]

[dhparker]

The photos are great. It really helps to see what you're all talking about.

Donna

[madratdan]

Hi NZcaver,

In our phone stash we have two of the EE-8 phones in working order. They are the heaviest, but they also work quite well. We mainly use them as entrance control phones due to them being the heaviest phones we own. They are also the clearest sounding ones we have. Here in Colorado, the caves we use them in are dry, so is our climate and storage area. We basically have no humidity to speak of, thus we also have vintage cars running around, all over the place.

We have 5 TA-312's, that are still working with several laying around for parts. This is also the type the fire department bought, and the type we have stored in Glenwood Springs. I believe they have at least four up there. In that area of the state, the caves are wet and of the Alpine variety. This is by far the most common phone we own and use. I'm guessing they are from the Korean war era.

We also have two of the TA-1 style phones. Like your description states, they are light weight, but very hard to communicate with unless they are the only two phones on the line. They work great for listening in and fixing problems and breaks in the line with.

The EE-8 and TA-312 use D cell batteries to boost their signal strength, so we have a core group that checks all our rescue gear on a yearly basis and replaced expendable, like the batteries for the phones.

I've also added 6' jumper wires with alligator clips to the phones so the they can be connected to the phone line easier. this gives the operator a lead to help hook up to the wire with, and position the phone out of the way. Inside the canvas cases we keep a small pair of wire cutter/strippers, electrical tape, pencil and paper, and a small piece of scotch brite to clean wire connectors with. There are also instructions for use and troubleshooting that I created and laminated for each phone.

Thanks for posting the pictures NZ.

[Brian Roebuck]

Dan it sounds like y'all have it goin on with the rescue phones! I have seen local rescue teams here in Tennessee with similar equipment but I can't remember which of the three types they actually have. I don't think they used the smaller more portable ones though and likely used one or the other of the green phones. Most caves are wet and muddy around here and that probably has an effect on what phones work best. This is a good thread!

[NZcaver]

dhparker said:

The photos are great. It really helps to see what you're all talking about.

Donna

Those are the field phones - now here's a few shots of cave radios being used....




Cave radio field day at the Alabama convention in 2005. The loop antenna is on the left, and the radio (a modified CB mobile unit with VLF transverter) is in the cooler to the right. The cooler just made it easier to carry around in that cave. Brian is the guy in the photo.




Cave radio testing in Arizona, at slightly higher than "normal" cave radio frequencies. We were sending voice, data and pictures between the surface and this passage in a mine (we also tested the same equipment in caves in the region, with favorable results). The radio used is a portable HF amateur transceiver, and the base of the (horizontal) whip antenna can be seen in the foreground. Ray is the guy in the photo.




Radio testing at Lava Beds NM, California. This time we're using CB handhelds, with a dipole antenna on the right consisting of 2 vehicle whips connected to a white plasic tube mast. We were comparing the range of the CB against VHF, which the park use. (Hence the handheld you can see in the right hand, with its whip antenna.) The CBs performed very effectively in this environment. Bill is the guy in the photo.

[All photos are mine.]

[L Roebuck]

nzcaver said:

Those are the field phones - now here's a few shots of cave radios being used....

Hey NZ, it seems you must be really involved with field phones and cave radios. Care to tell us more?