On Mar 30, 11:31*am, Jim Lux wrote:
I would imagine that the pattern of the helically loaded and the
unloaded will be quite similar at ANY frequency, until you get to where
the *diameter* of the assembly starts to be a significant fraction of a
wavelength.

A helical longer than a few degrees will exhibit transmission line
effects. A helical that is electrically 180 degrees long will have
essentially the same standing wave current envelope as a 180 degree
long open-circuit transmission line stub. EZNEC agrees.

John said his 180 degree electrically long helical outperformed his
electrically long 90 degree helical. The standing-wave current
envelope for the 90 degree helical is a cosine with the current
maximum at the feedpoint. The standing-wave current envelope for the
180 degree long helical is a sine wave with the current maximum point
in the middle of the helical. They would not have the same radiation
patterns. EZNEC agrees.

Again, I have modeled these conditions using EZNEC and I am reporting
the results. The "Currents" button will give the current magnitude/
phase for each segment in the helical.
--
73, Cecil, w5dxp.com