I have been using an AV-640 for 5 years.
Once a year, I lower it and clean all mechanical connections end to end.
Small wire brush. All aluminum connections to screws etc.
On the 17 m stub, if it vibrates too much on windy days, the screw joints
between each segment loosen. You really have to whale down on those joints
with pliers to make sure that they are tight.
Another thing to check, and I had this problem, the plastic isulators from
stub to center radiator might be burned. Like a charcoal track. In that case
you have to replace the insulator. The carbon absorbs moisture and makes a
conductive path to the main radiator.
I am not sure what caused this on my 640. I may have tried to load it
accidentally on 160 or 60 meters. That puts a high voltage at the tip of the
stub.
Dan Schaaf
K3ZXL
"In the Beginning there was Spark Gap"
www.k3zxl.com
----- Original Message -----
From: "GEORGE COSMETIS" <cosmetis@msn.com>
To: <towertalk@contesting.com>
Sent: Wednesday, February 03, 2010 8:00 PM
Subject: [TowerTalk] Hy-Gain AV-640 freq.shift
>
> The AV-640 works very well for me,except when it rains. The 17 meter
> resonance shifts to the low end and the ssb portion exhibits an swr of 4:1
> When dry the whole band is 2:1 Any ideas ? WA3CCI
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