On Mon, 31 Jul 2006 08:12:41 -0400, David George Johnson
wrote:

I want to put an eight wire vertical cage around a one hundred twenty
foot steel support for 80 meters. I can center feed the cage with
open wire line, which I assume will be more efficient than feeding the
steel at the bottom.

Hi David,

Certainly more complex as you would need to draw the feed off at right
angles for some distance (a quarterwave or more). Do you have a
second 60 foot tower at least that far away to string it out?

As Denny's experience shows, nothing really to be gained (except the
unstated bandwidth increase); and it could be done easier at ground
level feeding the skirt wires that are all connected to the steel mast
at the top. This cage is significantly larger than the mast diameter,
isn't it? It should be, or you are wasting your time.

The cage will not be in contact with the ground

That's fine.

or the tower.

It should be, at the top, as stated above.

My thought is that the wires will make a better
radiator than the steel, but I have no idea what the steel "core" will
do to the efficiency of the antenna. I have had no success in
modelling this antenna.

That is a fairly trivial task: select a sufficient "wire" diameter,
and choose the loss of steel. In the end, for a fat wire, it won't
matter much at the lengths and wavelength you are describing.

So my question is will the center fed, ungrounded cage dipole provide
any real advantage over feeding the tower at the bottom?

Nope.

73's
Richard Clark, KB7QHC