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Re: [TowerTalk] Sealing coax connectors

To: "Bob K6UJ" <>, <>
Subject: Re: [TowerTalk] Sealing coax connectors
From: "Jim Thomson" <>
Date: Tue, 17 Jan 2012 18:37:58 -0800
List-post: <">>
Dow corning DC4/5 is silicone GREASE !   It's  NOT RTV glop.     The  dc4/5 
is formulated for electrical connections.
The dc4/5   goes on the threads, the center pin.....and the mating female, 
that the pin goes into.  It's displaces moisture,
and  stops  microscopic arcing inside the connectors, where you have tiny 
microscopic air gaps between the pin + female.
Dc4/5 is typ 450-550 volts  per mil [ .001"]   Some of dow's tech notes list 
it as 1 kv per mil.   If the pin bears down hard
on the sidewall of the female, it makes contact. On the other side, where  a 
tiny air gap results, the  dc4/5 fills the void.
if the pin shifts about, the dc4/5  simply moves about as well, always 
filling the voids.   All the telco's  use it on 7-16
din connectors.   Andrew  supplies it in a small container with their 
connector's.   Ken Hirshberg, at Cal-AV  labs suggested
I use the dc4/5  on the 7-16 dins on his  baluns.  [ EB-3 variety].    You 
only apply a thin layer of it.  It's  good form -56 C
to well over 200 deg C.   OK, once the dc4/5 is applied, and connector 
cranked tight, then use your favourite water proofing
method.  BTW,  you can apply five times as much torque on any 7-16 din 
connector  vs  any Type N connector.  The 7-16
Din comes with the silicone rubber O ring.  The inner spring collet [female] 
is the  RF braid connection..and not the outer shell.
The inner spring collet + outer shell are  zero ohms between em though.

later... Jim  VE7RF

From: "Bob K6UJ" <>
Sent: Tuesday, January 17, 2012 8:13 AM
To: "[TowerTalk]" <>
Cc: "Jim Thomson" <>
Subject: Sealing coax connectors

> Jim,
> (I took the liberty of using a new subject for my response to this item in 
> your posting in the "PL259 insertion loss" thread.)
>> ##  and don't forget to use dow corning dc-4/5 on all the connectors, 
>> including threads, pins, and center females.  The 7-16 is clearly
>> the connector of choice for the bigger coax cables  [ it's ur only real 
>> choice].   For the smaller cables, like 213-U, and LMR-400, the
>> UHF QUALITY silver/teflon connectors are plenty good enough.  Type N for 
>> any size cable is a pita.  Odd ball connectors like C...and also
>> LC connector's are going out of vogue.
>> Later... Jim  VE7RF
> Jim,
> I havent used a silicone sealant in my connectors before but the Dow 
> Corning silicone sounds like a good plan.  For outside connectors I wrap
> with Scotch 2228 self sealing  tape, then wrap with scotch 88 tape, then 
> finally brush on Scotch Coat.  This has worked well for outside 
> connectors,
> taking the connectors apart later on they are always nice and shiny.  I 
> will try the Dow Corning silicone before the tape treatment.
>  One question though, can the connector be taken apart, cleaned up and 
> reused after using the silicone ?  I normally wouldn't reuse the 
> connectors
> but if they were new connectors it would be nice to be able to tie into 
> the connector again, for instance adding on a longer section of coax.
> (I'm talking about the threaded connection, not taking them apart and 
> resoldering)
> Bob
> K6UJ


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