Cecil Moore wrote:
Roy Lewallen wrote:
But most often when you see an antenna inventor or seller claim that
his antenna "can't be modeled" by NEC, EZNEC, or other programs, it
just means that modeling fails to show the extraordinary performance
he claims for it. That's simply a failure of the program to include
the effects of magical properties and wishful thinking in its
calculations. I've come to regard such claims as a red flag
indicating a probable exaggeration of antenna performance.

I wish I could remember the correct spelling for the antenna
I tried to model. Something like "Lentine". It is a dipole
of sorts made from shorted and open sections of balanced
transmission line. I tried modeling it with wires in EZNEC
and got all sorts of errors. It looked something like this:

+--------+--------+--------FP--------+--------+--------+
+------ +------ +------ ------+ ------+ ------+

Anyone remember the correct spelling for that antenna?

Google for "Lattin antenna". (Too many "lentils", Cecil :-)

One of the first hits is http://www.g3ycc.karoo.net/lattin.htm which
shows a good sketch. The antenna is made from sections of 300-ohm ribbon
or tubular feeder, configured as a string of quarter-wave stubs that
progressively make the dipole shorter as the frequency increases.

The modeling challenge is that the ribbon operates in two different
modes at the same time: a radiating common mode with a velocity factor
of say 0.95; and a non-radiating "stub" mode with a VF of about 0.8. The
problem is to model both modes simultaneously, for the whole string of
stubs, without changing the physical dimensions of the real antenna. I'm
not sure if NEC can do this, but maybe Roy can comment?


--
73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek