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Re: [TowerTalk] STUF Weather Proofing compound...

Subject: Re: [TowerTalk] STUF Weather Proofing compound...
From: K8RI on TT <>
Date: Mon, 03 Oct 2011 22:40:09 -0400
List-post: <">>
On 10/3/2011 7:40 PM, Guy wrote:
> Has anybody used this as coax connector weatherproofing solution?  See

I take it you are asking about "STUFF" and not "coax seal"?

Both Scotch and MMM make a self sealing "rubber" tape with mastic.  The 
stuff bonds to itself.
They also make a putty like substance that appears to be the same as 
"coax seal" such as GE 8880 High Voltage putty.

They all work pretty much the same. As for "STUFF" I'd much prefer to 
use Dow Corning's DC-4 and DC-5 "Dielectric" compounds which were 
designed for high voltages at high altitudes.  When they do break down, 
the result is still an insulator.  DC-4 was originally used to 
waterproof and seal spark plug boots on B-17's to prevent arcing at high 

Thing is a 5 ounce tube is $16.45 from Aircraft Spruce

A word of warning about flooding connectors which they are doing with 
"STUFF".  It and several other compounds work fine for sealing/flooding 
connectors *BUT* and that is a serious BUT, it is not a good idea to 
flood all connectors in a coax run.  Flood the one at the antenna to 
prevent moisture entering the coax, but remember that coax is going to 
breathe.   A coax run with several connectors in the run that are sealed 
will under go some pretty drastic pressure changes internally with 
temperature changes.  Up here this time of year the coax can go from 
freezing at night to well over a 100 degrees on a sunshiny day.  Coax 
out in the sun can feel quite warm on a pretty cold day.   The pressure 
change is in psi, not inches of water.  There are few tapes and seals 
that can withstand that differential.  Every coax connector in the line 
then becomes a potential spot for moisture ingress.  IF on the other 
hand the antenna end (or top) connector is sealed and flooded while the 
rest of the connectors are simply weather proofed so the coax can 
breathe naturally along its length, the pressure between the outside and 
interior of the coax will at most be a couple inches of water pressure.

However a coax run that "breathes" into a moist basement is likely to 
breath in moisture that will condense. "Generally" most coax ends in a 
heated room rather than a moist basement.  With 10 or 15 feet of coax in 
the house where it will stay warm, it is unlikely any humidity breathed 
into the coax will condense.  It'll just breath back out into the room 
the next time the coax warms up outside.

Most often we never notice as the temperature may not swing that much or 
the basement may not be that humid, of course part of it may be due to 
not very many hams actually flood connectors.


Roger (K8RI)
> Thanks in advance, Guy


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