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Re: [TowerTalk] Dow Corning High Vacuum Silicon Grease

To: Garry <g.drummond@verizon.net>
Subject: Re: [TowerTalk] Dow Corning High Vacuum Silicon Grease
From: "Roger (K8RI)" <K8RI-on-TowerTalk@tm.net>
Date: Fri, 11 Apr 2008 16:21:58 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Garry wrote:
> I was wondering if there's another Dow product under the same name 
> specifically made for RF connections? 
> Tony -K2MO
>
>
> Hi Tony,
>
> I remember seeing what I think you are looking for at 
> "*http://radioworks.com/catalog07web.pdf*.";  It is called *STUF*.
>   
A note of caution when sealing/flooding connectors in coax.  FLOOD ONLY 
ONE  END!
Flooding each end of a piece of coax does not let the coax breathe in 
the normal manner.  Heating in the day time will build pressure which 
will force air out of the coax through the flooded material.  When the 
coax cools it will generate a substantial pressure drop.  This much 
pressure drop in a one gallon metal can will cause considerable 
deformation.  So it will draw in air through the flooding material 
usually forming voids that may reseal. This type of breathing can cause 
condensation inside the coax, usually in the braid although with some of 
the older coax using a hollow dielectric it can be a problem within this 
area as well.  (I've found the inner conductor corroded as far as 8 feet 
above the bottom connector.).  It should go without saying,  the coax 
run should be unbroken with no flooded connectors between the one at the 
antenna and the one at the rig.   However with long runs terminating in 
a basement or cool space, considerable condensation can occur in the 
coax just like it does in conduit

I have flooded connectors in several runs in the past.  I have only one 
flooded at present which is at the base of the AV-640.  The connector in 
the matching network is not the most water proof and condensation tends 
to form in the box, not to mention gunk from wasps getting in there.

As a personal opinion (developed over many years) I prefer to not use 
flooding unless I think it absolutely necessary as the problems can 
outweigh the benefits under normal conditions.  (don't ever drop the end 
of the coax containing the flooded connector on the ground.  Dirt in 
that stuff is very difficult to get out)

If I had a run that required flooding connectors that would be up long 
term I'd invest in flooded, direct burial coax on which to use those 
flooded connectors.

73

Roger (K8RI)
> 73,
> Garry - WR4R
>
>
>
>   
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