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#21
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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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