Topband: EZNEC Model earth for Inv. L Re: EZNEC Shunt Feed Model Gain

[John Rogers]

>George K8GG wrote:-
>When I model it as a shunt
>fed tower, base grounded, with 50 feet of 1.6 inch OD pipe about 27 inches
>from the center of the tower as the shunt feed rod, the gain drops to
>about 0 (zero) dbi. The radiation pattern, etc. stays the same.
>Is this a fault of EZNEC4, or does the shunt feed truely reduce the gain
>of the antenna? Thanks for your thoughts,
>73, George

I have been having similar problems trying to model my shunt fed antenna and 
others with EZNEC5, so many thanks George, Dan, Jerry, Guy for postings. 
Before adjustment of segments, wire locations, etc. recommended by Jerry and 
Dan I was getting up to 2dB model loss when using no-loss perfect earth. It 
seems to vary with each antenna configuration used.

I would appreciate advice from Group which earth is recommended for best 
accuracy when modelling an inverted L. Real-mininec-earth or real 
high-accuracy-earth?  Am getting around 2dB difference between the two 
methods (+1 and +3dBi).
Also, should a loss resistance be put in series with real high accuracy 
model radials to simulate earth impedance?

With thanks,
73
John G3PQA



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