Actually, from eight years use of the Gap Titan vertical, I can confirm Lew
McCoy's original observation, (in CQ magazine), in reviewing another Gap
center fed vertical model, that these are less noisy than bottom fed quarter
wave verticals.
The Gap feed point is at an off center point much like a dipole but one side
is shorter since it is vertical over earth and its end effects. The coax
then, passes inside the lower aluminum tubing element, and out near its
bottom end. This provides a waveguide beyond cut off filtering effect to
vertically polarized noise in the typical urban environment of low or earth
mounted verticals. Mine is elevated about six feet over poor earth in the
middle of the back yard. The feeder leads off the connection point across
the yard just above head level to enter the shack.
As L. B. Cebik has modeled, vertical dipoles like the Gap do not benefit
from earth radials to any significant degree, and I do not have auxiliary
radials. Just like a horizontal half wave dipole; a Vertical half wave
dipole is a complete antenna unto itself.
-Stuart
K5KVH
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