[Elecraft] something new, but not under the sun

[Ron D'Eau Claire]

Oh, yes, Hey's book is still around. I often recommend it to Hams who are
trying to get an overview of antennas without delving into math or modeling
programs. It's a great read - just under 100 pages filled with explanations,
ideas and anecdotes. 

Hey's reports that the antenna 8" (20 cm) underground showed about 16 dB
less gain than a dipole 0.3 wavelengths above ground. 

That is, running a K3 at 100 watts into the underground antenna would put
out just about the same signal as a 4 watt KX1 into an elevated antenna. 

That's one way to get "QRP" out of a K3, Hi! 

The old story (goes back into the 1930's IMX - maybe farther) is based on
the idea of the earth producing an "image" of an antenna above ground
antenna. For example, a grounded 1/4 wave vertical monopole is naturally
resonant was explained saying there's an 'image' of the missing 1/4
wavelength created in the earth. Similarly, a horizontal antenna above the
ground exhibits radiation patterns as if it were twice the height above
ground from an "image" antenna in free space. 

So, extending the idea, if one pumped RF into a wire underground, there
should be an "image" above the ground in free space that radiates as well.

Unfortunately, that's where "science" collapses into a heap of grins and
chuckles. I'm sure Larsen E. Rapp, W1OU, expounded on it more than once in
his annual QST articles. 

Still, if you can withstand the attenuation, it is a way of getting an
antenna that no one can see. And, for receiving, on ground or underground
wires generally produce superior S/N ratios than elevated wires as Stephen
noted. Overall static and noise tends to be attenuated at ground level more
than the signals.

73,

Ron AC7AC



-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Stephen Prior
Sent: Sunday, June 12, 2011 12:35 AM
To: Elecraft
Subject: Re: [Elecraft] something new, but not under the sun

John Heys G3BDQ's book 'Practical Wire Antennas' published in 1990 by the
RSGB describes such an underground antenna in some detail on pages 79-80.  I
don't know whether the book is still in print or in an electronic format
anywhere.

They are very quiet on receive it seems ......

73 Stephen G4SJP