HFU HF Underground
Technical Topics => Equipment => Topic started by: bandarr3000 on February 25, 2019, 1712 UTC
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I could run a LoG around the perimeter of my back yard, but I would prefer to bury it if I could, for appearance sake. Can anyone recommend burying the LoG just below the surface (insulated wire, of course)? Thanks.
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You're joking of course ?
Actually you may not be, Im not sure?
To answer your question, No, well you can bury it but it would be a good Earth rather than a good Aerial.
Str.
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No, you don't want to bury it. But you can tack it down so it is just at the dirt level, and it will be mostly hidden by grass. Maybe buy some green insulated wire to help. ;D
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No joking, just curious. :-) I'll buy a few hundred feet of green THHN. The perimeter of my back yard is ~300 feet. Those little metal landscaping staples would be the least conspicuous.
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There have been many studies on hfunderground antennae, most from a military/civil defense aspect. The cheapest yet most effective will likely be made from solid center insulator coax like rg8, with the shield removed, the farther the earth is from the wire the less loss so insulator thickness comes into play but keep in mind these studies more or less were looking at transmit and receive characteristics, not reception alone. Also note that being below ground causes the velocity factor to be altered from normal, so less "antenna" is required to meet a specific freq characteristic if that is desired.
As you likely suspect, the deeper it's buried the more losses increase. A few inches is good for emp resistance, the shallower the better if all you care about is being able to mow over it, some folks just pin a insulated wire to the ground and let the thatch grow over it, no burial needed. Kinda like those dog fences.
I've a arrl antenna handbook that has excerpts from a fedgov study where various hf antennas were utilised deep inside an abandoned mine, and the results were promising. In the same article was noted a great signal increase on 80m for a vehicle traveling thru a deep rock canyon, apparently the canyon acted as a slot antenna. Neat stuff!
https://apps.dtic.mil/dtic/tr/fulltext/u2/783274.pdf
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A little early in the season, but this might help illuminate the subject:
http://www.arrl.org/technology-eclectica
Scroll down to:
A Compact All-Band Antenna
QST April 1957
The whole article may be useful, especially the section "The Image Principle", p. 136 & 138.
Good luck! ;)
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N6BV addressed this in QEX a while back. Short answer is that even the normal “absorption” of the wire by your grass is going to significantly hurt reception.
You can read his article here:
https://rudys.typepad.com/files/qexjul-aug-2016-bog.pdf
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A little early in the season, but this might help illuminate the subject:
http://www.arrl.org/technology-eclectica
Scroll down to:
A Compact All-Band Antenna
QST April 1957
The whole article may be useful, especially the section "The Image Principle", p. 136 & 138.
Good luck! ;)
Lol wish I had a ferrite core 3 inches in diameter and 3.5 feet long. That would be the king of permeability!
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A little early in the season, but this might help illuminate the subject:
http://www.arrl.org/technology-eclectica
Scroll down to:
A Compact All-Band Antenna
QST April 1957
The whole article may be useful, especially the section "The Image Principle", p. 136 & 138.
Good luck! ;)
Hope everyone note that "a little early in the season" means that we are just before the 1st of March, not just before the 1st of April !
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Yep I really though he was pull our plonker!
Ah well....
Str.
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There was a pipe version of it ran for CW comm's on the Western Front in WWI. They hooked the thing to a spark gap tx and a generator and pumped it straight in the ground. It was a real worm raiser. as they were pumping kW's in that soggy ground at roughly 10% efficiency. The troops in the trenches on both sides just loved it when they fired up.
During WWII, it was about the only form of domestic ham comm's. The Civil Defense boys tried it for awhile until they discovered the phone or banging on the door and yelling "Turn that damned light out, Fansome!" was easier. Ground telegraphy moved into the world of wartime ragchewing.
We had a 2ft. screwdriver with an insulated handle. We took a couple of battery clips and attached them to the handle end that fed a heavy duty AC cord to it and a heavy duty AC plug at the other end. We'd drive the thing in the yard, get up on the porch, switch on the power and watch those worms surface. Cut the power, gather 'em up and go fishing.
Learned it from a great-Uncle, a WWII era ham and Civil Defense man. His pith helmet still graces my bedroom.
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if it was for tx i would say throw it on the ground and let the rf fly :D
i remember a station being heard nationwide on a wire laying on the ground ;)
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There used to be a few gutter tx men, but vinyl gutters ended that.
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come on now Pigmeat , load up the steel roof . or you could try some shopping carts in a parking lot sometime .
been there done that it worked