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Re: Cushcraft 738XB



Also remember if sealing with silicon RTV make sure you use one made for
electrical circuits.  The standard silicon will corrode electrical circuits
given some time and moisture.


Mike
K4HN
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-----Original Message-----
From: Bob Bruninga <bruninga@nadn.navy.mil>
To: jbblack@mindspring.com <jbblack@mindspring.com>
Cc: AMSAT-BB <amsat-bb@AMSAT.Org>
Date: Sunday, January 16, 2000 12:13 PM
Subject: Re: [amsat-bb] Cushcraft 738XB


>On Sun, 16 Jan 2000 jbblack@mindspring.com wrote:
>
>> Yesterday, I climbed my short tower (23') and removed the switchbox on
the
>> antenna.  I had sealed it with silicon to keep water out.
>
>I'm no expert, but I think that if you seal anything, then it must also be
>100% hermetically sealed (air tight) or you will get more problems than if
>you just leave it open.  Here is what I have heard about making things
>"water proof":
>
>1) Guarantees failure when the thing leaks on the top and cant drain out
>the bottom.  Floods all exectronics
>2) Day heating (high humididty) and nighttime cooling (condensation) will
>keep the circuits bathed in mositure..
>
>My rule of thumb, is:
>
>1) NEVER completely seal the "bottom" there must be a drain hole.
>2) Let it breathe freely
>3) Paint it white to keep it cool...
>4) NEVER leave exposed aluminum boxes if you want to keep it cool.
>Aluminum in sunshine can reach very high tempratures.  White will stay
>cool in brigh summer sun... (difference between absorbtivity and IR
>emissivity)  The factors are a factor of 10! between aluminum and white.
>
>----
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>

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