Gene Fuller wrote:
. . .
I tried to adjust the frequency downward, but the segment length limit
is reached for the coil model. I redrew the coil with only six segments
per turn, rather than eight. Now the frequency can be lowered to about
3.94 MHz without EZNEC guideline check warnings.
. . .

Of the Guideline Check warnings, the one about short segment length can
most often be ignored without a problem. If in doubt and where
practical, do a test case. For example, model the inductor with a wire
through the middle directly connecting top and bottom and with a source
in the middle. Note how the source reactance changes with frequency to
see that it follows what it should theoretically do. Another test you
should run when in doubt is the Average Gain test, described in the
manual. Either is probably adequate to have confidence in the results.

The Guideline Check warnings are based on NEC-2 recommendations. I've
found that you can often make segments much shorter than the
recommendations without causing a problem.

Roy Lewallen, W7EL