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.

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
insufficient by my standards, six are barely worth chasing the numbers
and I typically use 16. One such example, complete with a link to the
design can be found at:
http://home.comcast.net/~kb7qhc/ante.../Cage/cage.htm

It deviates only by a small degree, but could prove a useful boost in
adding the longer element after opening the top end of the thick
radiator.

73's
Richard Clark, KB7QHC