Hi Steve, I am not an expert on this but Ralph has used this kind of pipe
for his 166.5 Part 5 beacon. Now, he has had troubles with burnt up tube,
now solved I believe. As far as I understand, the problem comes with corona
discharge which carbonises the plastic which then conducts and eventually
burns up. The "trick" I think is to attach anti-corona rings to the end
insulator so the high voltage terminates on a largish radius-of-curvature,
rather than a cut wire end ( which is most likely to stimulate corona) I
think Ralph has pics on his web site. Jim recommends a ring of thick wire
about 3ins diameter. I think this should also be done wherever there must be
sharp changes in direction, unless you can dress the changes in direction
into a smooth curve. Corona certainly seems to become a problem above about
150 - 200 W on 136kHz.
Hopefully Jim will add his comments
Cheers de Alan G3NYK
[email protected]
----- Original Message -----
From: "Steve McDonald" <[email protected]>
To: <[email protected]>
Sent: 20 February 2004 19:08
Subject: LF: Antenna Insulators
Has anyone had success using white PVC pipe (say ~ 1.5" dia) for
insulators?
I am wondering if a 12 -18" piece at the voltage ends of my flatop would
be
enough to prevent any flash-over?
Steve / VE7SL
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