In article , Ian White GM3SEK
wrote:

That isn't a complete model of this particular antenna. The missing part
is the velocity factor of the twin-lead when acting as a stub, which
means that the electrical length of the stub is different from the
physical length. Which of those two lengths would you use in the NEC
model?

The answer is easy for a single-band model; but it's not so easy to
create one NEC model that will be valid for all the bands this antenna
is designed to cover.

Hello, Ian. You would use the physical length for all wires that are
interconnected and/or separated by free space. After all, that's what
we're trying to model. You still must decide how many electrically-small
segments would constitute, say, a 1 foot length of conductor. The higher
the frequency, the more segments you will need. If transmission line is
to be connected between segments, NEC has tools for doing that. BTW, my
experience is with LLNL's NEC-4 (FORTRAN-77 source code) rather than the
commercially-available packages. Sincerely,

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