In article . net,
Wimpie wrote:

Problem exists how to get reliable insulation to split driven element
and support rod which is exposed to RF voltage ?
Fiberglass is told to be sensitive creating conductive coal brigdes
which creates true resistive short at driving point ? (at least one
fiberglass tubing is done so... gap was 2 inches )

Assuming power of about 1 kW and a HW dipole (say 60 Ohms), the
voltage will be about 350Vp. I can hardly imagine that a plastic gap
of 0.05m will degrade to failure because of tracking.

On the other hand, if the original poster is attempting to drive this
antenna off-resonance, with open-wire feedline and a wide-
impedance-range transmatch / "antenna tuner", then it's entirely
possible that the feedpoint will sometimes be "looking into" a much
higher impedance, and that a matched drive will result in very high
voltages at the feedpoint. Even a coax-feed antenna might have this
problem, I suppose, if the split element is being driven by something
like a delta match which has a relatively high impedance-
transformation ratio.

From what I see in a short Google-search, fiberglass *can* be
hygroscopic, depending on what resin was used to bind the fiberglass.
A fiberglass rod which was made with a somewhat-hygroscopic resin
(e.g. polyamide) might tend to behave badly in the face of high RF
voltages, whereas a rod made with a non-hygroscopic resin might be
fine unless dirty or wet.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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