"Cecil Moore" wrote in message
et...
Jimmie D wrote:
I made one of these sleeve antennas for 10M with the folded back
shield,
put a KW on it and it arced through the black vinyl.

It's a standing wave antenna. The voltage at the end
of the shield is approximately 20 times the voltage
at the feedpoint. For a KW, that's more than 5 kV,
too much for ordinary coax.

I have 160 watts available. ... about 90 volts at the feedpoint, so a
whopping 1800 at the end of the shield. (Might want to keep the mike gain
throttled back.)

OR ... use a larger braid over a spacer of some kind and solder it to the
coax braid at the feedpoint. The spacer could be a piece of plastic pipe
slipped over the coax at the outset. Actually, the braid doesn't really have
to be braid. It could be a piece of copper pipe. The tuning operation
would need to be slightly different; I'll need to keep a few inches of the
original coax near the feedpoint. I'll tune it by sliding the pipes and
bunching up the coax at the feedpoint. Or tune it by adjusting the length of
the center conductor element.

I wonder ... if the pipe were sufficiently large, it would tend to broadband
the antenna. I know of this effect at UHF. How about 10m???

I'm looking forward to this. g