Re: Underground Antenna Experiments on 160 meters.

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
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