The Gap Titan is a shortened vertical off center feed dipole, thus no
line isolator should be needed. It is already a complete dipole
antenna, enhanced by linear loading and stub matching on its Lowest
band. The off center feed is to account for the greater earth coupling
of the lower end vs. the upper half dipole. My Titan sits atop a pipe
such that you can walk under the horizontal radius rods.
The Titan, on some bands, provides more isolation from ground effects by
the radius rods supporting the 40 meter resonating wire that encircles
the lower leg end of the vertical dipole. No RF in the shack effects
have been experienced with my Titan, nor some other Gap models owned by
local hams, and we all live in an area with poor RF character to the
local earth. I hear from a lot of Titan owners since I published a
summary of an industry paper on off center fed vertical dipoles, and no
Titan owner has complained of RF on the outside of the coax. The coax
should lead off from the vertical dipole as directly as possible. In my
installation, I had elevated coax back to the house roof edge, and the
coax then crossed the attic before dropping into the interior shack.
-Stuart Rohre
K5KVH
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