Ground wave transmission, was G-line

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Original poster: Steve Conner <steve@xxxxxxxxxxxx>


> Ground wave transmission, Tx =  2 stakes in the ground 1/4 wave spaces

This I do believe. I have a couple of cookbooks with plans for 
various ham radio antennas, and there are a few underground antennas 
in there :-o

The construction article mentioned that they had tested an 
underground half-wave dipole (buried 8 inches down) alongside an 
ordinary half-wave dipole elevated 0.3 wavelength above ground. The 
underground antenna was 16dB worse. But that is still quite usable 
considering that the underground placement seems to block out 
interference so you can use more receiver gain.

This is not quite the same as Robert's setup where he drove stakes 
into the ground and passed the RF current through the ground itself. 
These antenna systems used a 1/2 wave wire dipole buried in the 
ground and presumably excited waves in the ground through induction. 
But I reckon the effect would be pretty much identical.

The only thing I'm not sure about is how you can develop waves in the 
ground alone. These underground antennas were tested by talking to 
other hams who were using normal above-ground antennas. My reading of 
the situation is that the ground-air interface "leaks" so that you 
produce waves both in the air and the ground, no matter whether you 
use a buried antenna or an elevated one. But that is just my opinion 
and up for debate.


Questions to ponder:

If you dug a huge pit, and buried a HF beam antenna firing vertically 
up to the sky, would you get ground waves or air waves? :-) In the 
light of the recent thread on A&E TV, maybe we could bury some 
lawyers with field-strength meters down there too, and ask them to 
report back to us. :-))

Would underground antennas still look 16dB worse, if both ends of the 
link were using one? Or is the 16dB loss caused by trying to receive 
ground waves with an airborne antenna?


Source: "Practical Wire Antennas", Heys, J.D., Radio Society of Great 
Britain, 1989, pp. 79-80

Steve Conner
http://www.scopeboy.com/