On Sep 16, 9:41*am, "Bill Ogden" wrote:
I am a little confused since
the tower (and, I assume, the outside of the coax) is an intentional part of
a half-sloper antenna.

There are two sources of common-mode current. A choke at the resonant
dipole feedpoint reduces the common-mode current conducted onto the
outside coax braid. Unfortunately with the tower being a radiator and
the coax tied to the tower, inducted common-mode is the major problem
and difficult to solve. A choke at the antenna feedpoint will have
little effect on inducted common-mode current. I wonder if you are
frying any earthworms along your buried coax? :-)
--
73, Cecil, w5dxp.com