There is going to be a LOT of coupling from the two halves of the cage
dipole to the tower. It sounds like a recipe for disappointment to me.


As far as a radiator, the steel will work OK because it's got a lot of
surface area. You could always cage it with wires connected at the top
and bottom if you're worried about the conductivity.

I'd feed it at the bottom if I was lucky enough to have a 120 foot
vertical pipe :-)

73,
Dan