[TowerTalk] COAX SEAL

[kq2m at kq2m.com]

There should be another part to this discussion that I have not yet seen 
mentioned.  Coefficient of Thermal Expansion.

If the connectors are water tight/air tight, then in theory no taping of 
connectors should be necessary if the connections are all 
electrically/mechanically sound and very tight (I fill in all four PL259 
braid holes with completely melted and flowing solder) and no large 
physical stress in placed on them.  Furthermore, if tape is used and 
water manages to get in, then it can potentially be sealed which over 
time could create problems.  But changes in heat/humidity can cause 
condensation INSIDE the wraps anyway.  So not using anything to wrap the 
coax/connectors would allow immediate exposure to the elements and 
simultaneously allow for moisture drainage away from the 
coax/connectors.

But none of that addresses HOW and WHEN those physically tight 
connections might become less tight.  Enter Coefficient of Thermal 
Expansion.

We all know that various metals get hot faster than the outer jacket of 
coax, in response to direct sunlight and hot ambient temperatures in the 
Summer. Conversely, we know that objects (like connectors) will shrink 
in size response to the cold more than coax will shrink because of 
differences in the Coefficient of Thermal Expansion (the reverse of how 
they all expand with an increase in temperature).

Because connectors will shrink more in response to colder temperature 
than coax will, a tight connection will begin to loosen and will allow 
for water to get in.  This is especially true in Winter in more Northern 
climates.
So that "waterproof" connection becomes non-waterproof.  And if water 
can get in, ice can form and expand the gap and damage the the coax or 
connectors or both.  By using tape and sealant we are already protecting 
against that.

But note that this is already happening anyway in microscale because the 
coax jacket and the connectors are neither perfectly smooth nor exactly 
the same shape, so there are already tiny ridges and depressions on the 
surfaces of the coax jacket and the connectors that are allowing air and 
moisture to get in even though you can't see it.  But these tiny gaps 
can easily be seen under an electron microscope even though is not 
visible to the naked eye.  Bottom line: Pro or not, you really should 
use some sort of quality tape/wrap anyway on ANY connections, including 
around connectors.

73

Bob, KQ2M




On 2024-03-09 18:51, Steve Maki wrote:
> Gary,
> 
> Thanks, I was debating whether to start from scratch again with a post; 
> whew.
> 
> I'll just add that a two layer system can work, IF the stretchy 
> weatherproofing layer is not the type that gums up the works (the 
> connector) such as butyl rubber or coax seal. Use a silicone tape 1st 
> layer with almost any type of good UV protection on top.
> 
>  If you insist on using the gummy sticky stuff, use it in a three layer 
> system with a 1st layer of courtesy wrap made of almost anything. The 
> gummy sticky stuff should extend well past the end of the courtesy wrap 
> so that that it bonds to the coax. Commercial weatherproofing is almost 
> always three layer.
> 
> -Steve K8LX
> 
> On 03/09/24 7:00 PM, Gary NA6O via TowerTalk wrote:
>> Lots of chatter indeed… Here is my famous summary of all the 
>> weatherproofing methods I noted as of a few years ago. Read and enjoy.
>> https://na6o.com/amateur_radio/ewExternalFiles/Connector_Weatherproofing.pdf
>> 
>> Gary NA6O
>>