Nick wrote:
Cecil, I understand what you are saying, but still why not use the
outer shield of the coax as one of the radials, and simply choke off
the coax just before it enters the shack? I also don't want to add
what may be a useless choke at the antenna's feedpoint, since that
would decrease the antenna system's efficiency due to the choke's
resistive losses...

Unless the coax is up and in the clear, common-mode power is
probably wasted whether you choke or not.

If your choke at the shack happens to be placed at a common-
mode voltage-maximum/current-minimum, it will be ineffective.
One reason for placing a choke at the antenna feedpoint is
that is probably the maximum current point where the choke
has a good chance of being most effective.
--
73, Cecil http://www.w5dxp.com