Tony,

The best thing to do is insulate the wire from the rod at the top and
bottom. Space the wire from the rod by one or two centimetres.

The rod will not be near to 1/2-wave resonance and the antenna will
behave very much as if the rod did not exist.

Remember that loss induced in the rod will be negligible when the
resistivity of the rod is high, or is also very low. I would imagine
the loss would be greatest when the end-to-end rod resistance is in
the order of 150 ohms.

But loss will be induced in the rod only when the rod is near to
1/2-wave resonant.
----
Reg.