Low Frequency Cave Radio

[+Ether Bunny]

A 16 year old kid from New Mexico has designed a low frequency radio to communicate in caves.

I wonder whether this technology could be used to triangulate from several broadcast sites in order to navigate like GPS underground. Anybody know anything about this?

 

http://www.npr.org/templates/story/story.p...;cc=nh-20100131

[+ecanderson]

A 16 year old kid from New Mexico has designed a low frequency radio to communicate in caves.

I wonder whether this technology could be used to triangulate from several broadcast sites in order to navigate like GPS underground. Anybody know anything about this?

 

http://www.npr.org/templates/story/story.p...;cc=nh-20100131

 

Cool stuff below dating back quite a ways. Pretty unique web site - devoted entirely to electronics + following big holes in the ground . Adding data was a natural next step for the technology. Kinda slow at ULF speed, though!

 

http://caves.org/section/commelect/main.ph...guts=speleonics

 

That said, you'd have to wonder if there is any practical way to use this kind of technology for triangulation that far below ground. I don't think the signal propagates in a very straight line as it penetrates.

[7rxc]

A 16 year old kid from New Mexico has designed a low frequency radio to communicate in caves.

I wonder whether this technology could be used to triangulate from several broadcast sites in order to navigate like GPS underground. Anybody know anything about this?

 

http://www.npr.org/templates/story/story.p...;cc=nh-20100131

 

Cave radio has been around for a long time, some work better than others. You could do something like that, but the equipment might be limiting... I'll have to read that article and some others...

 

My gut feeling is that if you want to triangulate broadcast radio sites... you could do it with conventional

RDF techniques... most AM handheld receivers have a ferrite rod antenna inside which can be quite directional. Or easily made more so if moved outside the box and linked to the radio with an rf attenuator pad ( to reduce signal strength) That would give a bi directional line of position, the intersection of 3 would

give a likly search area. Similar but fancier one could use FM radios with some electronic measuring of the phase angle to give a direction. Or simply use several examples of switched antenna arrays (hand held).

None are very precise though so the search area could be large if you used commercial stations. It's easier to track a hidden transmitter. Out here we use personal avalanche beacons for obvious reasons (avalanches). There are the old style beacons that use a mostly discontinued frequency.. those can be found out there fairly cheaply, since we don't hunt them anymore... new ones are on a different frequency and going digital rapidly. I've thought of using the old style adapted to solar power for the transmit.

Whatever works for the receivers... One can also get 'lost equipment or dog' trackers.. not to mention the Brickhouse child locators... (wouldn't recommend that though for parks!).

 

Doug

[+keehotee]

It's been used for cave surveys for at least 2 years...

 

Novel use of radio-location for a ground investigation at Pen Park Hole, Bristol, UK

[+Gitchee-Gummee]

VLF was used for U.S. submarine communications for a while. It got dumped because of cost (and probably better stuff we don't know about yet).

[7rxc]

VLF was used for U.S. submarine communications for a while. It got dumped because of cost (and probably better stuff we don't know about yet).

When did they do that? Just interested... Dang subs was the expensive part IMHO.

 

Doug

[+Gitchee-Gummee]

Dismantled one in the U.P. of Michigan say about 10 yrs ago. (VLF)

 

EDIT: It involved a HUGE antenna array (encompassing multiple counties) totally underground.

Edited February 1, 2010 by Gitchee-Gummee

[+Ether Bunny]

Cool stuff below dating back quite a ways. Pretty unique web site - devoted entirely to electronics + following big holes in the ground . Adding data was a natural next step for the technology. Kinda slow at ULF speed, though!

 

http://caves.org/section/commelect/main.ph...guts=speleonics

 

That said, you'd have to wonder if there is any practical way to use this kind of technology for triangulation that far below ground. I don't think the signal propagates in a very straight line as it penetrates.

 

Thanks. It's not so much radio per se I was thinking about, but a way to use simultaneous broadcasts from multiple close sources with a receiver to judge wavelengh timing and thus triangulate position.

 

Great link, thanks again.

EB

[7rxc]

Snip...

 

Thanks. It's not so much radio per se I was thinking about, but a way to use simultaneous broadcasts from multiple close sources with a receiver to judge wavelengh timing and thus triangulate position.

 

Great link, thanks again.

EB

 

You are describing things like LORAN and even in an altered state, the GPS system. You can read up on those by yourself. There are also several methods to use TDOA (Time Difference of Arrival) for roughing out a location based on a single signal... all require precise timing and complex calculation.

 

Of course, GPS uses positional data rather than radio waves themselves for this... but the timing is everything regardless and was an update on pure wave systems. If you care to email through my profile, I can discuss what you have in mind... I'm sure others could as well.

 

BTW, watch when you delete parts of quotes... you have to leave the first part with quote name= in... works better...

 

Doug

[+ecanderson]

Thanks. It's not so much radio per se I was thinking about, but a way to use simultaneous broadcasts from multiple close sources with a receiver to judge wavelengh timing and thus triangulate position.

 

Great link, thanks again.

EB

The reply was to note several things. 1) The concept of subsurface RF communication isn't new. Adding data to the comm is just another way of doing the same thing. 2) Subsurface radiolocation already exists, but isn't of a very high resolution - that can create some special problems in caves (see below). 3) My later sentence you didn't quote was meant to address your question, and does, I believe, answer it. RF propagation through a lot of earth isn't going to be on a very direct line, making simple RF triangulation to any level of precision difficult.

 

Adding a complication, the GPS method of the time of arrival of multiple signals, doesn't help. Propagation speed through (or more accurately, around) various layers of materials (including water!) is going to foul that up pretty good.

 

Worse, the thing that isn't being considered anywhere in our discussion is that caves are very often not two dimensional. You can have many vertical levels with passages and rooms that are above and below one another. In order to get all of that straight, what would be needed is RF triangulation that is accurate enough to discern depth differences of only a few feet from a considerable distance underground. Not now. Perhaps not ever. I suspect that what already exists may well be as good as it gets... which may be good enough if you just need a general idea and aren't trying to seriously map a cave.

Edited February 14, 2010 by ecanderson

[7rxc]

RF propagation through a lot of earth isn't going to be on a very direct line, making simple RF triangulation to any level of precision difficult.

 

Adding a complication, the GPS method of the time of arrival of multiple signals, doesn't help. Propagation speed through (or more accurately, around) various layers of materials (including water!) is going to foul that up pretty good.

 

Worse, the thing that isn't being considered anywhere in our discussion is that caves are very often not two dimensional. You can have many vertical levels with passages and rooms that are above and below one another. In order to get all of that straight, what would be needed is RF triangulation that is accurate enough to discern depth differences of only a few feet from a considerable distance underground. Not now. Perhaps not ever. I suspect that what already exists may well be as good as it gets... which may be good enough if you just need a general idea and aren't trying to seriously map a cave.

 

That's what I was getting at as well... However I suspect that the project in mind isn't neccessarily cave related... I have a gut feeling that it is a surface project... I've asked for detail, but haven't had any response so far. As you seem to know, propagation and such isn't all that predictable above ground either.

Always liked foxhunting myself... and hiding. Even if he does come up with an rf based system, I don't know how he would 'equip' the masses... us. I don't see provided gear surviving long... Anyway we've tried and still waiting for contact there...

On the other hand, I'm getting more ideas here myself... hmmm.

 

Doug

[+ecanderson]

As you seem to know, propagation and such isn't all that predictable above ground either.

Especially at the moment in the grand solar "cycle"(?), it can even just cease to happen altogether! Any 10m equipment has been sitting around in moldy basements in recent years. Think we're headed for another (shudder) Maunder Minimum? Imagine finding the entire HF spectrum useless for anything but Morse. A 'no code' license would have been pretty useless back in the 2nd half of the 1600's.

On the other hand, I'm getting more ideas here myself... hmmm.

Was that the sound of an evil cache being planned??? Something in this conversation has certainly given me an idea for a really wicked puzzle cache.

[7rxc]

 

On the other hand, I'm getting more ideas here myself... hmmm.

Was that the sound of an evil cache being planned??? Something in this conversation has certainly given me an idea for a really wicked puzzle cache.

 

I get ideas all the time... Not all of them good ones, but some are... I get bits here and there and put it in the blender of my tired old brain... This time it's this thread, the one about the Geocaching robot.. etc.

There are of course many ways to triangulate a position... GPS is sort of that... but I've been thinking about something I read about visual coding... for industrial robots... simple graphics that can be read and in combination, tell the machine where it is etc. The space station boys use a dot system for that in the same manner... it tells the reader, position, direction etc. in 3d.. Might be fun to do a night cache which requires a resection on sets of firetacks or similar... in order to zero the cache. One might even be able to make a simple device to do the zeroing... if the tacks reflect active IR like they do visible... anyways... late here.

 

BTW... All radio licences were pretty useless at any point in the 1600's. The gear was terribly inefficient as well.

 

Doug

Edited February 15, 2010 by 7rxc