> and the literature is full of interesting diagrams relating the height
> of the dipole above, not only physical ground... but also, above a
> virtual image somewhere below ground. This in-the-ground image was
> responsible for radiating an in-phase or out-of-phase signal with the
> above ground wire creating interesting take-off angles that are
> responsible for a good, great or a very poorly working antenna.
Your tounge-in-cheek post is important, because it points out there
really is no such thing as an "in the ground antenna image". The
mental or paper picture an "image antenna" paints is a very incorrect
I e-mailed the ARRL when they, quite incorrectly, explained in
detail about how a radial system forms a vertical antenna "image"
below the antenna. The answer was in response to the question "what
do radials do?" in a "The Doctor is In" column.
(The incorrect response, given to someone trying to understand
what ground systems do, went uncorrected. My e-mail was received
by but went unanswered by the author of the "image" response.)
The image antenna is a "rough tool" useful for calculating
or mentally visualizing the effects of ground extending for a large
distance in many directions of the antenna on patterns.
The image isn't really there, in the dirt below the antenna, at all.
With a vertical, the image is formed by the ground several
wavelengths from the antenna, not by the ground near normal short
(radial L<1/2 wl) radial systems.
73, Tom W8JI
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