In article , Cecil Moore
wrote:


The problem that EZNEC has with this antenna, as I understand it,
is that the same pair of parallel wires has common-mode current
in them on some frequencies resulting in a high VF and differential
mode current in them on other frequencies resulting in a low VF. I
don't know how to model changing VF's with EZNEC without changing
the physical length of the wires as frequency is changed.

Hello, Ian, and I guess I don't see how this is a problem provided you
have described the antenna geometry correctly and have chosen the
appropriate number of segments at the evaluation frequencies of interest.
Velocity factor and other electromagnetic phenomena are implicit in the
solution for the current distribution on the structure. Now, if
dielectric material is distributed in the structure that does complicate
things a bit. Can you point me to some further info on the antenna in
question? I trust this is not another one of those situations where there
is an attempt by vendors to "reinterpret" Maxwell's equations (or explain
things that Maxwell "left out").

I would encourage frequent users of NEC to subscribe to the mailing list
at . Lots of practical discussion there IMHO.
Sincerely,

John Wood (Code 5550) e-mail:
Naval Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337