Thanks Dan.
I removed the dielectric from the tube - the tube was sealed. Certainly
moisture could be the cause as it occurred suddenly this winter. I would
not call the tube sealed particularly well. At one end there was the
dielectric wrapped in electrical tape and the other end was sealed with RTV.
I will probably replace the dielectric and dry out the tube (just to make
sure).
Anything else I should consider?
Scott
_____
From: danzimmerman@gmail.com [mailto:danzimmerman@gmail.com] On Behalf Of
Dan Zimmerman N3OX
Sent: Sunday, April 26, 2009 12:00 PM
To: Scott MacKenzie
Subject: Re: [TowerTalk] 6M Beam being weird
The only thing I can think of left is to replace the coax less shield inside
the gamma.
What else can it be?
Is it open so that you'd notice water in between the dielectric and the
tube, or is it all sealed up?
If it's nominally WX sealed, I'd check inside because the high dielectric
constant of water can make even a thin layer screw up a capacitor pretty
well.
I built a cap for my 60 foot vertical's 30m matching network that was a
couple layers of overhead transparency film between some copper sheets.
Worked great until one day this spring where condx were just right to get a
little tiny bit of condensation making a thin film of water, mostly in
between the plastic layers.
"SWR" light on my radio was blinking... it made enough of a change to go
well over 3:1 SWR. I didn't try to figure out how high... I just replaced
it with an air variable that I'd freed up from another project.
73
Dan
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