Hello Richard,

Richard Clark wrote in
:

On Sat, 14 Mar 2009 21:33:15 GMT, Owen Duffy wrote:

My questions a

1. To what extent is b) equivalent to a)?

Hi Owen,

To no extent as far as I can tell without modeling. I don't think the
phases are going to equivalent.

Ok. Your view is contrary to common explanation... but of course that
doesn't make it wrong.

NEC models of the wire construction at a) show in phase operation, but a
small distortion of the pattern due to common mode current on the stub...
so they support the common explanation in the phase aspect, but not in
respect of the stub causing phase change with no other effects.

The explanation of b) as a) where the stub is relocated coaxially sounds
appealing, but that explanation might be wrong.


2. How is b) modelled in NEC?

This takes some presuming of your intent, and my presumption, given
the symmetry of the two smaller elements (why two otherwise?), is you
are attempting to portray a skeletal sleeve with them. Two is

You seem to have mininterpreted my ASCII art, and that would be easy to
do. I am describing at b), two coaxial tubes, the lowest tube is 1/4
wave, the longer tube is 3/4 wave. The lower tube ends are connected, and
fed between ground and the bottom of the tube assembly.

See the model that I have posted in response to Roy.

Thanks.

Owen