I run my open wire tuned feeders up through the middle of the tower. The
tower doubles as a quarter-wave vertical on 160, so running the feedline
inside the tower improves isolation of the feeders when in the vertical
antenna mode. Also, the tower provides some shielding to the feedline when
using the feeders and dipole. The tower is on a base insulator, and when
using the dipole hung at 119', I can ground or unground the tower across the
base insulator with virtually zero effect on the tuning of the dipole. The
dipole acts as top loading for the vertical, so it is really more like a
vertical tee than a simple quarterwave vertical, with measured base
impedance on the order of a couple hundred ohms (plus substantial
j-component), rather than 36 ohms purely resistive.
I would expect some reduction in lightning problems running any kind of
feedline cable inside the tower rather than on the outside, plus I believe
it would be mechanically more secure.
I space my feeders using strips of plexiglas mounted every 10', supported by
the horizontal rungs of the tower. While climbing the tower, I loosen up
the feeders at the bottom end using turnbuckles, to allow my feet to extend
unhampered inside the tower.
Don k4kyv
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