Just a silly question, did you consider the C-pole antenna ?
It could be a solution to you problem as it does NOT need any radials.
It is a much ignored antenna. I made intensive simulations with 4nec2
and the results are very interesting. The only problem is the feed
point on which you need a choking system.

73, Patrick TK5EP
http://tk5ep.fre.fr


Buck a exposé le 13/03/2007 :
I have a situation where I would like to install a vertical wire above
a fiberglass pole I have in the center of the yard. However, I must
keep the coax off the ground so I can only feed it about 7 feet from
the ground so people and the mower can get underneath. (rental
property).

I want to setup a 20 or 30 meter vertical and run ground radials from
the base of the pole where the wires can be buried. Is it possible to
feed the antenna above the ground plane? for example, I have ground
radials connected to a seven foot vertical wire, the shield side, and
the center side of the coax would continue upwards to the top, or
appropriate height on the pole.

Thanks
Buck
N4PGW