RF transmission from a mine

On Mar 27, 9:14 am, John <sampson...@gmail.com> wrote:
> Can anyone suggest modern options for transmitting a few bits of
> information from deep in a mine over RF? The transmitter, battery, and
> antenna should be capable of being carried by a person. The receiver
> is outside the mine and can have much more size, weight, and power.
> Specifically, I'm interested in:
>
> RF frequency
> Waveform
> Reference clock accuracy
> FEC
>
> Thanks,
>
> John

Google is you friend.

vlf mine radio

Analysis:
Analysis of VLF loop antennas on the Earth surface for underground
mine communication
Gogoi, A.K.; Raghuram, R.
Antennas and Propagation Society International Symposium, 1996. AP-S.
Digest
Volume 2, Issue , 21-26 Jul 1996 Page(s):962 - 965 vol.2

Reports of Bureau of Mines Technology Studies"
http://www.cdc.gov/NIOSH/Mining/pubs/pdfs/h0346045.pdf

Commercial product:
http://www.msha.gov/regs/comments/06-722/ab44-comm-84.pdf

Dale B. Dalrymple

John wrote:
> On Mar 27, 1:35 pm, Vladimir Vassilevsky <antispam_bo...@hotmail.com>
> wrote:
> 
>>John wrote:
>>
>>>Can anyone suggest modern options for transmitting a few bits of
>>>information from deep in a mine over RF? The transmitter, battery, and
>>>antenna should be capable of being carried by a person. The receiver
>>>is outside the mine and can have much more size, weight, and power.
>>>Specifically, I'm interested in:
>>
>>>RF frequency
>>>Waveform
>>>Reference clock accuracy
>>>FEC
>>
>>The path losses in the ground can be coarsely estimated as:
>>
>>loss = 1dB/m x sqrt(F/30kHz)
>>
>>At VLF, in addition to that, you have the 1/R^3 law due to the near
>>field. The ambient noise follows ~1/F law.
>>
>>Hence, for any practical purpose, the operating distance is limited by
>>50 meters or so, unless you have a chain of repeaters, leaky waveguides
>>  or something like that.
>>
>>Vladimir Vassilevsky
>>DSP and Mixed Signal Design Consultanthttp://www.abvolt.com
> 
> 
> Thanks. I had already read about lower frequencies penetrating better;
> it is the skin effect. I haven't seen that approximation though, do
> you have a reference for it?

I design the underground cable locators and the horizontal drilling 
tracking systems. So I did some of R&D work on the propagation. The 
approximation is very coarse and rather pessimistic; the soil 
condictivity can vary by the factor of 1000. However, in VLF for this 
application the main problem is not the path losses but the 1/R^3 near 
field and the 1/F ambient noise.


> At this point I'm not wanting to rely on any infrastructure (conduit,
> wires, leaky coax, etc) inside the mine, but it is possible the
> receiving site could have something like this: 
> http://en.wikipedia.org/wiki/Beverage_antenna

If you are not relying on any infrastructrure, then your operating 
distance is likely to be about 30m or even less then that.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com