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Richard Clark · September 27th 06, 06:36 AM posted to rec.radio.amateur.antenna

On 27 Sep 2006 02:34:40 GMT, (John E. Davis)
wrote:

Does EZNEC report
the oscillations when the frequency increment is on the order of 0.01
MHz? What version of NEC does EZNEC use?

Hi John,

I've been using various flavors of E(L/Z)NEC for more than a decade
and I've never seen such dramatic cogging of the data that was not
attributable to construction (notably fractals). Your data is
stranger yet in having correlated noise on the left, and uncorrelated
noise on the right.

When I run the model at the resolution you suggest (0.01MHz), yes, I
do see some very fine cogging. It is on the order of 0.5 Ohm reactive
up tick which, for example, translates to a shift from 1.60:1 to
1.62:1 on a generally downward slope. When I run again with the
double precision math, this goes away. Both curves do not exhibit a
flat bottom, but rather an asymptote.

You can observe this quite readily on the download, free version of
EZNEC for yourself.

73's
Richard Clark, KB7QHC