RF transmission from a mine

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

On Fri, 27 Mar 2009 09:14:03 -0700 (PDT), John <sampson164@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.

Leaky coax? See, for a general discussion,
<http://telephonyonline.com/wireless/mag/wireless_trouble_tunnels/>

One vendor's glossy:
<http://www.afltele.com/resourcecenter/specifications/fiberopticcable/pdfs/LeakyCoaxialCable.pdf>

-- 
Rich Webb     Norfolk, VA

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 Consultant
http://www.abvolt.com

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
> 

As others have said, it would be best to first determine what (if any) 
conductors run into the mine. Lighting, other power lines, metal pull 
cables, tracks, etc. You'll almost have to rely on coupling into those.

-- 
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

On Mar 27, 1:35&#4294967295;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
> &#4294967295; 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?

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

John

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?
> 
> 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
> 

Be careful with very low frequency stuff, the defense guys might not 
like that.

Possibly you can find publications from these guys:
http://www.cmpdi.co.in/Services/Mining%20Electronics.htm

-- 
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

John <sampson164@gmail.com> wrote:
(snip, Vladimir wrote)

(>> The path losses in the ground can be coarsely estimated as:

>> loss = 1dB/m x sqrt(F/30kHz)

> 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 will guess that it is the absorption due to water.
 
> 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:

There does have to be a hole out of the mine, right?
Otherwise how do people get in?  At some frequency and
power level it will be easier to follow the mine shaft.

Otherwise, VLF (or lower) is used by submarines communicating
while under water.  As I understand it, the resonant 
frequncy of the earth is 7Hz.  That probably takes a 
lot of power, though, but at resonance it is hard for
the enemy to locate you.

-- glen

On Mar 27, 5:11&#4294967295;pm, glen herrmannsfeldt <g...@ugcs.caltech.edu> wrote:
> John <sampson...@gmail.com> wrote:
>
> (snip, Vladimir wrote)
>
> (>> The path losses in the ground can be coarsely estimated as:
>
> >> loss = 1dB/m x sqrt(F/30kHz)
> > 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 will guess that it is the absorption due to water.
>
> > 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:
>
> There does have to be a hole out of the mine, right?
> Otherwise how do people get in? &#4294967295;At some frequency and
> power level it will be easier to follow the mine shaft.
>
> Otherwise, VLF (or lower) is used by submarines communicating
> while under water. &#4294967295;As I understand it, the resonant
> frequncy of the earth is 7Hz. &#4294967295;That probably takes a
> lot of power, though, but at resonance it is hard for
> the enemy to locate you.
>
> -- glen

I'm thinking about a trapped miner. Normal infrastructure is broken,
the only thing left is seismic or RF. I've read about VLF pulse
transmitters in the miner's lamp, received with big loops above.

John

On 28 Mar, 00:41, John <sampson...@gmail.com> wrote:
> On Mar 27, 5:11&#4294967295;pm, glen herrmannsfeldt <g...@ugcs.caltech.edu> wrote:
>
>
>
>
>
> > John <sampson...@gmail.com> wrote:
>
> > (snip, Vladimir wrote)
>
> > (>> The path losses in the ground can be coarsely estimated as:
>
> > >> loss = 1dB/m x sqrt(F/30kHz)
> > > 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 will guess that it is the absorption due to water.
>
> > > 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:
>
> > There does have to be a hole out of the mine, right?
> > Otherwise how do people get in? &#4294967295;At some frequency and
> > power level it will be easier to follow the mine shaft.
>
> > Otherwise, VLF (or lower) is used by submarines communicating
> > while under water. &#4294967295;As I understand it, the resonant
> > frequncy of the earth is 7Hz. &#4294967295;That probably takes a
> > lot of power, though, but at resonance it is hard for
> > the enemy to locate you.
>
> > -- glen
>
> I'm thinking about a trapped miner. Normal infrastructure is broken,
> the only thing left is seismic or RF. I've read about VLF pulse
> transmitters in the miner's lamp, received with big loops above.

The problem is that the transmitter needs to
be almost as large as the recievers to be
efficient. If it isn't efficient you need a
large power supply, which migh not be practical
as personal equipment.

But maybe you could deploy those sorts of things
around the mine? Or use seismic transitters?
I know some mines are equipped with seismic arrays
to locate microfracturing. Use a powered hammer
to bang on the walls. The problem with this would
be that it requires that you hit bedrock, not
stray boulders.

Rune

John <sampson164@gmail.com> wrote:
 
> I'm thinking about a trapped miner. Normal infrastructure is broken,
> the only thing left is seismic or RF. I've read about VLF pulse
> transmitters in the miner's lamp, received with big loops above.

Such as after a cave in.  I would think the thickness of
the cave blockage would be less than the distance to
the surface.   Also, if there is conduit for lamps some
signal would follow that out.  

-- glen