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Underground Antennas

Discussion in 'General Technical Questions and Answers' started by N2NH, Oct 31, 2005.

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  1. N2NH

    N2NH Ham Member QRZ Page

    For years I've been coming across stories about underground antennas. Some claim they make good stealth antennas, some say they were used by spies in World War II. Does anybody know if they actually work? I'm not looking to get great performance, but to see if it can be used in a Ham hostile enviroment as a stealth antenna.

    Thanks
     
  2. AE4FA

    AE4FA Ham Member QRZ Page

    There's one that runs through large portions of Wisconsin and Illinois. It is (or was) used for ELF communications with submarines. Don't really know if it's still in use.
     
  3. AG3Y

    AG3Y Ham Member QRZ Page

    Smart-alacky answer " Only in caves! ! ! " [​IMG]

    I love it when I can fine a good web page to answer my questions ! Try this one:

    http://www.elfrad.com/

    73, Jim
     
  4. K6PME

    K6PME Ham Member QRZ Page

    That looks interesting.
     
  5. K7KBN

    K7KBN Ham Member QRZ Page

  6. WA4ILH

    WA4ILH Ham Member QRZ Page

    First, the Navy's facility at Clam Lake was decomissioned several years ago.
    Second, Don't know about "underground" but when I lived out in West Texas, where the ground conductivity was Really Really bad, I knew an extra class operator who lived in a house with restrictions who would run a long wire out his window along the ground for about 50 feet to the back of his property. Worked lots of DX on this. (with a tuner of course)
    Tom WA4ILH
     
  7. K8ERV

    K8ERV Ham Member QRZ Page

    Bet it heats up the worms.

    TOM K8ERV Montrose Colo
     
  8. K7FE

    K7FE QRZ Lifetime Member #1 QRZ Page

    Stealth it is, great performance it is not.

    Subsurface (underground) antennas have been thought of for about as long as radio has been around.  They received a boost in interest during the "cold war" atomic tensions with the Soviet Union.  It was thought that underground antennas would survive nuclear attack, even if your house did not, so every bomb shelter needed an underground antenna for radio reception or transmission.

    Practical info:
    1 Velocity factor is dielectric dependent, so if you bury an antenna in soil (which is a dielectric) then the physical length will be shorter than the same antenna mounted above ground.  Expect very low velocity factors of 40% to 25%, depending on depth, conditions and soil type, so physical length will be half or less the length of an above ground antenna.

    2.  Soil attenuation will reduce signals substantially.  A dipole buried eight inches below the surface in “normal” soil will have a attenuation of about 16 dB over a 40 meter dipole mounted at 0.3 wavelength above ground.  Attenuation will increase with depth.

    More information may be found in RSGB publication “Practical Wire Antennas” by John Heys, G3BDQ or ARRL “Antenna Compendium Vol 1” article titled “Subsurface Antennas for the Amateur”.

    73,
    Terry, K7FE
     
  9. WA4ILH

    WA4ILH Ham Member QRZ Page

    Are you kidding, Do you think that anything can still be alive down there after Texoco and Amoco are through pumping their chemicals into oil depletion wells?
     
  10. WA9SVD

    WA9SVD Ham Member QRZ Page

    Ah, marinated worms! Micky D's would be jealous! <GRIN>
     
  11. K7MH

    K7MH Ham Member QRZ Page

    Does this mean if I bury a 20 meter beam with the director face down in the ground I will have a better long path signal?? Sure would be a son of a gun to rotate!! [​IMG]
     
  12. VK4XJB

    VK4XJB Ham Member QRZ Page

    Closest I have tried is an 80m dipole lying on the ground. For the people I normally listen to or talk to I estimated the signal was 10 - 15dB down compared my normal dipole.

    It was a stormy night so I did not bother trying to transmitt with it. The static crashes were bad enough you wanted the highest erp you could get. For receiving I loved it. Set the agc to either fast or off, af a long way up and use the rf gain control for volume. I was able to get a far better signal to noise ratio than I could with the normal dipole.

    Did not think much of the idea of using it for tranmitting but it was great for receiving.
     
  13. W5ALT

    W5ALT Ham Member QRZ Page

    Since both companies have been merged with others, actually they have stopped. (I assume you meant Texaco.)

    But what is an "oil depletion well?" I've never heard of those.

    73,
    Walt, W5ALT
     
  14. KC0KBH

    KC0KBH Ham Member QRZ Page

    If you had a trencher with a vibrating plow and a lot of wire making one would be pretty easy.
     
  15. N2NH

    N2NH Ham Member QRZ Page

    Thanks to all that answered. I came across an old magazine that had a story on underground antennas and wondered if I could get away with one here in the city. Too bad they perform so poorly; it looked pretty good on paper. I suppose I'll stick to a joey out the window.
     
  16. VK4XJB

    VK4XJB Ham Member QRZ Page

    Why you would you hang a baby kangaroo out the window?
     
  17. N2NH

    N2NH Ham Member QRZ Page

    Because nobody's shown me how to tip a cow. Gotta do something when your bored. Sure entertains the neighbors.
    [​IMG]
     
  18. K8ERV

    K8ERV Ham Member QRZ Page

    NH, you are a better clown than I am . My hat is off to you. --

    TOM K8ERV Montrose Colo
     
  19. N2NH

    N2NH Ham Member QRZ Page

    I doubt it and you're much quicker on the trigger than I am. Nobody scoops me more than you and CGC (Charles). [​IMG]
     
  20. K7KBN

    K7KBN Ham Member QRZ Page

    When you tip a cow, is it 10% or 15%? What are the guidelines?
     
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