Hi Eric,
Congratulations on your eloquent and informative response to Jay's pastural
plea. As you state the "connection" loss can easily be eliminated with as
few as two well balanced radials. However, the near-field loss is not
reduced as it would be with an extensive ground radial system. I agree that
a ground screen below a sparce elevated radial system is effective in
reducing near-field losses in the absence of an extensive radial system.
The size of the ground screen can be reduced considerably by shortening the
elevated radials using a series inductor and/or a bigger tophat. Bandwidth
may be reduced but the benefits of a small counterpoise are usually important
especially on small lots. With a top loaded short vertical and a shortened
counterpoise the radiation resistance is low but the losses can be greatly
reduced by using low ohmic resistance materials. The system is resonated and
may be fed at a convenient point not necessarily at the electrical center.
However, I suggest using a serious balun or choke on the coax at the
feedpoint to assure that all the current stays in the resonant antenna and
not leaked to the lossy earth. By the way, there is no radiation resistance
in a properly balanced elevated radial system.
As far as the far-field losses as you say; "There is very little that the
average ham can really do about it". I suggest choosing your site well. If
you are near saltwater or a marsh in the direction you work DX this loss will
be low. Personally, I chose a mountain top with steep drop-off making the
effective height for the far-field very high. This particularly greatly
improves the very low angle gain.
I agree that the near field losses can be around 4 to 6 db depending on the
earth and surroundings. However, losses in the 10 to 40 db are possible due
to "connection" losses with a poor ground. This is easily eliminated with a
good resonant counterpoise.
I hope this is helpful to the vast majority of topbanders that can't put out
60 or more 300' ground radials.
73, Darrell, N6DX@aol.com
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