Dave Platt wrote:
Use a simple wire or rod radiator tied to the center conductor of the
coax, no radiator tied to the shield, and a length of feedline which
is an even multiple of a halfwave (at the exterior shield's
velocity-of-propagation) back to ground or the transmitter, serving as
a counterpoise?

Seems to me, the "ground" would cause reflections, turn
that "even multiple of a halfwave" into a standing-wave
antenna, and maybe be more efficient than an Isotron?
--
73, Cecil http://www.w5dxp.com