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Old May 20th 04, 05:30 PM
Dan Richardson
 
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On Thu, 20 May 2004 08:40:47 -0700, Roy Lewallen
wrote:

However, the feedpoint radiation resistance of a half wave vertical is
very high -- typically higher than the ground resistance. For a given
power input, a relatively small current flows into the base of the
antenna, so very little current flows in the ground. Consequently, the
ground loss is low, and there's no need to decrease its resistance with
radials.


From a practical view point you are correct, but for those who wish to
nit-pick adding radials will, according to NEC, result in an increase
in performance.

At about 0.35-wavelength from the base of the ½-wave monopole the
ground current peaks ( Brown, Lewis and Eastein) . The ground
losses are just further away from the base of the antenna.

Modeling I found that comparing a full-bore ground system (120
half-wavelength radials) to a single eight-foot ground rod (average
ground) the difference reported was about 1 dB.

Considering the cost difference, for me, there are more practical ways
of gaining 1 dB.

Danny, K6MHE