Hi Tom,

K7ITM wrote in
:

....
I suppose that R.W.P. King disagrees with the "common explanation."
He makes it quite clear that there is interaction of the antenna field
with the stub perpendicular to the axis of the antenna wire, and that
the coaxial stub does not interact in the same way and the antenna
performance is therefore different. (Antennas chapter of Transmission
Lines, Antennas and Wave Guides, King, Mimno and Wing.) This is why I
like using a feedline to guarantee the phasing. It can be done by
driving collinear dipoles with equal lengths of transmission line, or
by using an arrangement like the "coaxial collinear," where the
radiating elements are outer conductors of coaxial transmission lines
used to insure that the multiple feedpoints are at least fed in-phase
voltages (and you have to consider that the currents are not exactly
in phase).

That it interesting that Prof King declares that there is more than just
a transmission line action with the external style of stub.

An NEC model of a) works well, showing in phase operation and a nice
pattern. I have played around with two stubs of shorter length on
opposite sides of the vertical and stacked on top of each other, and they
worked fine (ie in phase current distribution with zero near the stubs)
at about 0.15+ wavelenths each... which doesn't fit with a propagation
delay around the conductor path explanation. Interesting!

I am trying to support the common explanation of the coaxial colinear in
my diagram b) using NEC, but I haven't yet been sucessful.

Owen