A 180 or 190 degree vertical radiator presents a few different
problems compared to one 90 degrees long, due to the high voltage at
the feedpoint. You can have ground loss there, but since it is more
of a coupling problem than a return current problem, the earth shield
is usually a copper mesh that extends out around the pier about 20
feet. Think in terms of the loss at the ends of an inverted V when
the ends are anchored near the ground.
Since the feedpoint is high voltage, the way in which the base of the
radiator is insulated becomes more important, and the ball gap must be
adjusted accordingly, and access to the area kept more secure to
prevent casual contact with the excited base of the radiator. If a
concrete pier is used to hold a ceramic base insulator, the pier must
be bypassed with copper ground strap so it is not part of the voltage
gradient between the mesh and the radiator, as concrete is conductive.
For ham (in my opinion) none of this is worth the trouble, and I'd go
with a quarter wave antenna.
73
Rob
K5UJ
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