Towertalk
[Top] [All Lists]

Re: [TowerTalk] COAX SEAL

To: Steve Maki <lists@oakcom.org>
Subject: Re: [TowerTalk] COAX SEAL
From: kq2m@kq2m.com
Date: Sun, 10 Mar 2024 11:57:14 -0500
List-post: <mailto:towertalk@contesting.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


_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
<Prev in Thread] Current Thread [Next in Thread>