The most common problem is if water gets into the traps (if your horizontal
antenna has them)

Some traps have drain holes and they should be oriented so the drain hole is
downwards

A friend had them upwards and the SWR would go way out of sight when it
rained, so he was off the air until the traps dried out.

We changed them, no problems even in a downpour


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"Roy Lewallen" wrote in message
...
The short answer is that water won't cause any problem, and even salt
water probably won't (except corrosion).

When water bridges across a driven element or to the boom (not by any
means the same as the Earth), you've put a high value resistor and
capacitor across the driven element or from the element to the boom. Pure
water is a good insulator but acts also like a lossy capacitor at RF; rain
water on an antenna will have some dissolved minerals so that reduces the
shunt R. The feedpoint impedance of a beam is quite low, so all you've
done is put a high value of impedance across a low value. The change is
therefore very small. This holds for half wave dipoles, quarter wave
verticals, and most other common antennas, too.

A few antenna types have high impedances at the feedpoint, like an
electrically short whip, or a full wavelength dipole. Although I don't
know of any rigorous tests, I don't think even these are commonly bothered
much by water.

Roy Lewallen, W7EL

Dan Jacobson wrote:
Can one in theory still transmit if rain
water creates a bridge across the driven
element, or even also to 'ground'?
A DC short circuit but not a RF short circuit?
Or is it just salt water that is worrisome?