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Underground Antenna Experiments on 160 meters.



 
 
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  #21  
Old July 30th 05, 12:47 AM
Michael
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This has been done since the beginning of radio. Nothing new. However, I am
interested in the sand antenna. I would love to hear more about working
antennas that exist entirely below ground. I am guessing but would say this
would not work on any band above 160 meters. I know the Navy has made huge
underground radiators at frequencies like 50 khz. I would be surprised to
hear that something as high as 1.8 mhz could be made to work.


"Reg Edwards" wrote in message
...

Some years back I buried a 30 metre (60-feet) auminium wire one spade
depth in my back garden. Wire was 1.5 mm in diameter. Soil
resistivity about 100 ohm-metres. To scientists that's 10
milli-Siemens. The near end of the wire came up in the shack. That's
under my kitchen sink. It's still there. Open-circuit at the far end.

As a counterpoise, something essential to tune it against, I erected a
wire in the form of an inverted-L. This was about 30 feet high and
overall length about 140 feet. I chose this length because it fitted
nicely into my back garden. The front garden is too short even for an
underground antenna.

On the 160m band I fed into it about 30 watts from a home-brew
transceiver so I can't provide for the record a manufacturer's type
and serial number. However I still have the transceiver which can be
inspected.

Despite a high local noise level of S-6 I was able to communicate up
to 60 miles with mobile stations in broad daylight on SSB. After
sunset I could easily communicate with most of Europe on CW.

I think a record of these buried antenna experiments should be kept
for posterity, alongside the famous biblical work of B,L & E.

By the way, as you see, I did remember to measure soil resistivity. It
was the first thing I did. What buried wire do you think I used to
measure it?
----
Reg, G4FGQ




  #22  
Old July 30th 05, 02:43 AM
Roy Lewallen
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Michael wrote:
This has been done since the beginning of radio. Nothing new. However, I am
interested in the sand antenna. I would love to hear more about working
antennas that exist entirely below ground. I am guessing but would say this
would not work on any band above 160 meters. I know the Navy has made huge
underground radiators at frequencies like 50 khz. I would be surprised to
hear that something as high as 1.8 mhz could be made to work.


I recall reading some years ago about underground antenna experiments
done by the military. I believe the were done well into the HF range. A
trench was dug, the antenna put into the trench but not in direct
contact with the soil, then the top was covered. The objective was to
make a concealed antenna for relatively short range communication. The
signals were much weaker than for an above-ground antenna (~30 dB if I
recall correctly, but I might not), but still usable for the purpose at
hand. This shouldn't be surprising.

Roy Lewallen, W7EL
  #23  
Old July 30th 05, 03:07 AM
Fred W4JLE
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You might be interested in the 1918 article on underground antennas.
http://www.rexresearch.com/rogers/1rogers.htm

"Roy Lewallen" wrote in message
...
Michael wrote:
This has been done since the beginning of radio. Nothing new. However, I

am
interested in the sand antenna. I would love to hear more about working
antennas that exist entirely below ground. I am guessing but would say

this
would not work on any band above 160 meters. I know the Navy has made

huge
underground radiators at frequencies like 50 khz. I would be surprised

to
hear that something as high as 1.8 mhz could be made to work.


I recall reading some years ago about underground antenna experiments
done by the military. I believe the were done well into the HF range. A
trench was dug, the antenna put into the trench but not in direct
contact with the soil, then the top was covered. The objective was to
make a concealed antenna for relatively short range communication. The
signals were much weaker than for an above-ground antenna (~30 dB if I
recall correctly, but I might not), but still usable for the purpose at
hand. This shouldn't be surprising.

Roy Lewallen, W7EL



  #24  
Old July 30th 05, 05:17 AM
Roy Lewallen
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Fred W4JLE wrote:
You might be interested in the 1918 article on underground antennas.
http://www.rexresearch.com/rogers/1rogers.htm


Thanks for the reference. A key observation from it is:

"One of the Naval experts present mentioned that it had been found that
the penetration of the ground wave component increases with an increase
in wavelength. This is an important fact and helps to explain the
operation of this new radio system, with its aerials buried in the ground."

I believe this method is still being used for communications to
submarines. It depends heavily on the very great skin depth and
relatively low attenuation in sea water at the VLF wavelengths used.

The buried antennas I was referring to operate, as far as I know, with
normal field propagation through the air, not through the ground.

Here are the skin depth in feet and attenuation per foot in salt water:

Freq Skin Depth Atten
ft dB per ft

10 MHz 0.23 37
1 MHz 0.73 12
100 kHz 2.3 3.7
10 kHz 7.4 1.2
1 kHz 23 0.37
100 Hz 74 0.12

And here they are for average ground:

Freq Skin Depth Atten
ft dB per ft

10 MHz 13 0.66
1 MHz 25 0.34
100 kHz 74 0.12
10 kHz 230 0.037
1 kHz 738 0.012
100 Hz 2300 0.0037

So communication through the ground or even salt water is practical at
low frequencies. High frequency is another matter, though. But that
doesn't preclude using buried antennas for sky wave propagation.

Roy Lewallen, W7EL
  #25  
Old July 30th 05, 05:20 AM
Roy Lewallen
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John Ferrell wrote:
I agree that it was an April issue and I think my old friend W8DMR
(Bill) may have written it. However, I was thinking it more in the mid
60's.

de W8CCW


My guess as to the date could easily be that far off. But if your friend
wrote it for QST or HR, he used a pseudonym -- I don't see his call or
name in the inclusive indexes of either magazine.

It must have been in CQ or 73. I can still recall the diagram, showing
the buried antenna and the dotted "image" above ground.

Roy Lewallen, W7EL
  #26  
Old July 30th 05, 02:10 PM
John Ferrell
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He may have used a pseudonym. He did prefer to write for CQ, they paid
a little bit where QST did (does?) not. I have been out of touch with
Bill since leaving the Central Ohio area.

As I recall, after he had one such artical published he received quite
a few letters from people who took it seriously.

de W8CCW

On Fri, 29 Jul 2005 21:20:08 -0700, Roy Lewallen
wrote:

John Ferrell wrote:
I agree that it was an April issue and I think my old friend W8DMR
(Bill) may have written it. However, I was thinking it more in the mid
60's.

de W8CCW


My guess as to the date could easily be that far off. But if your friend
wrote it for QST or HR, he used a pseudonym -- I don't see his call or
name in the inclusive indexes of either magazine.

It must have been in CQ or 73. I can still recall the diagram, showing
the buried antenna and the dotted "image" above ground.

Roy Lewallen, W7EL


  #27  
Old July 30th 05, 02:13 PM
John Ferrell
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That is great!

I will use that at the next Lios Club meeting and aso in my church
newsletter...

de W8CCW

On Fri, 29 Jul 2005 18:01:11 -0400, "Hal Rosser"
wrote:

My brother quit the power company when they were switching to "underground
utilities" - he got tired of burying those telephone poles so deep! And I
had to give up chicken farming because the county extension agent said I was
planting them too deep - I think I must have been planting them too near the
underground power lines.


"John Smith" wrote in message
...
Reg:

I can't even dream of burying a perfectly good, working, beautiful, sleek
antenna!

... I shall refrain from burying any antenna, before its' time ...

John



  #28  
Old July 30th 05, 03:44 PM
Fred W4JLE
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Back in the day, we received traffic from the station in Jim Creek while
submerged. They used a 13 mile array strung between 2 mountains. IIRC it was
on 18KC. CW only as any frequency shift would have put the finals out of
resonance. Much better methods today that remain classified.

I know we could receive it when submerged in the Red Sea.

"Roy Lewallen" wrote in message
...
I believe this method is still being used for communications to
submarines. It depends heavily on the very great skin depth and
relatively low attenuation in sea water at the VLF wavelengths used.

The buried antennas I was referring to operate, as far as I know, with
normal field propagation through the air, not through the ground.

So communication through the ground or even salt water is practical at
low frequencies. High frequency is another matter, though. But that
doesn't preclude using buried antennas for sky wave propagation.

Roy Lewallen, W7EL



  #29  
Old July 30th 05, 06:38 PM
Ed Price
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"Fred W4JLE" wrote in message
...
Back in the day, we received traffic from the station in Jim Creek while
submerged. They used a 13 mile array strung between 2 mountains. IIRC it
was
on 18KC. CW only as any frequency shift would have put the finals out of
resonance. Much better methods today that remain classified.

I know we could receive it when submerged in the Red Sea.

"Roy Lewallen" wrote in message
...
I believe this method is still being used for communications to
submarines. It depends heavily on the very great skin depth and
relatively low attenuation in sea water at the VLF wavelengths used.

The buried antennas I was referring to operate, as far as I know, with
normal field propagation through the air, not through the ground.

So communication through the ground or even salt water is practical at
low frequencies. High frequency is another matter, though. But that
doesn't preclude using buried antennas for sky wave propagation.

Roy Lewallen, W7EL






Did the Navy ever deploy the Long-Range Autonomous Homing Bottle?

--
Ed
WB6WSN
El Cajon, CA USA


  #30  
Old July 31st 05, 12:58 AM
Reg Edwards
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Roy. as you know, radio propagation through the ground follows exactly
the same laws as propagation through anything else.

All is governed by the resistivity, permeability and permittivity of
the medium, at a partcular frequency, and the geometry of the
interfaces between different mediums.

The problem of finding solutions to paricular problems lies only in
entering input data into a general purpose, number crunching computer
program, which I'm sure versions of it already exist.


 




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