According to the EZNEC manual, whenever you insert the direct
connection with the Sommerfield ground, NEC inserts an unknown
series resistance. If I switch to real mininec ground, I don't get any
warning (according to the manual, this is the preferred ground for
vertical elements with direct connections to ground). The results
with the direct connect to the real mininec ground look reasonably
close to the Sommerfield results with the direct connection (so perhaps
the warning with the sommerfield ground is unwarranted in this
particular case).
Anyway, too many variables and question marks with the computer
models in close to ground to give me much confidence in the
Nth decimal place results (its all giving me a headache). At this point I
suspect the best thing to do is abandon the computer and do the
final tweaking on the array (and the tower detuning) in the field
with real measurements. Besides I can't work any DX with the
computer model no matter how good I make the patterns look.
73 de Mike, W4EF............................
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