Waterproofing coax connections

[OkieBoyKJ5JFG]

I've been watching videos on protecting coax connections from the weather, and they're all demonstrating various combinations of multiple layers of self-adherent rubber tape, electrical tape, Vaseline, and I don't even know what else. Maybe this is a stupid question, and perhaps the answer should be obvious, but why can't you just use waterproof marine-grade heat-shrink tubing? Or at the least, use it over a layer of that rubber tape? Yes, it can be a little challenging to get off when you want to remove it because of the glue, but I've done it and it's not all that hard. Am I missing something?

 

[mmckenna]

I've been watching videos on protecting coax connections from the weather, and they're all demonstrating various combinations of multiple layers of self-adherent rubber tape, electrical tape, Vaseline, and I don't even know what else. Maybe this is a stupid question, and perhaps the answer should be obvious, but why can't you just use waterproof marine-grade heat-shrink tubing? Or at the least, use it over a layer of that rubber tape? Yes, it can be a little challenging to get off when you want to remove it because of the glue, but I've done it and it's not all that hard. Am I missing something?

Absolutely an option.
Trick is making sure you get the right size tubing so it'll cover the bulky part of the connector and still seal well around the coaxial cable. That can be difficult with large connectors, like N, and small coax, like RG-58 (but not impossible).

They make "cold shrink" sealing kits that will do this:

Gamma Electronics, Inc. - Cold Shrink 4.3-10 Applications to 1/4" Coax - SDL-CX-125 - Tessco

GAMMA ELECTRONICS' SDL-CX-125 silicone cold shrink, for 4.3-10 applications with 1/4 in coax or similar, 5 in long. Gamma's SDL cold shrink is a specially formulated pre-expanded silicone rubber shrink tube that does not require heat to shrink. It is supplied expanded over an easily removable...

www.tessco.com

But the de-facto industry standard is this:

https://www.telewave.com/wp-content/uploads/2016/12/TWDS-0502.pdf

I've used this method for nearly 30 years, and disassembled connections that have been up almost that long and they looked like new.

Some of the ham radio/hobby methods are OK, some are not. Vaseline will flow when hot and may leak out of the connector, or down inside air dielectric coax.
Usually the best method is to not put anything inside the connector and just seal it properly from the outside.

 

[OkieBoyKJ5JFG]

Absolutely an option.
Trick is making sure you get the right size tubing so it'll cover the bulky part of the connector and still seal well around the coaxial cable. That can be difficult with large connectors, like N, and small coax, like RG-58 (but not impossible).

It struck me as odd that nobody brought this up (as far as I could find), since it seems pretty obvious and considerably easier. I can see the issue with a bulky connector and a small cable, and I had thought that perhaps a couple of wraps of that self-adhesive rubber tape on the RG58 would make it thick enough for the heat-shrink to "take". However, at present, I'm going to be using LMR400, so I shouldn't have a problem with that.

Some of the ham radio/hobby methods are OK, some are not. Vaseline will flow when hot and may leak out of the connector, or down inside air dielectric coax.
Usually the best method is to not put anything inside the connector and just seal it properly from the outside.

I'm always leery of using things that weren't designed for the application (whatever that is). I did see a recommendation for a thin layer of dielectric grease on the threads, but I don't think I'd use Vaseline. I don't totally discount the experience of people who have been doing this longer than me, but I'd just rather use something that was designed for the job. Good to know about the Vaseline. I'll avoid it.

 

[mmckenna]

It struck me as odd that nobody brought this up (as far as I could find), since it seems pretty obvious and considerably easier. I can see the issue with a bulky connector and a small cable, and I had thought that perhaps a couple of wraps of that self-adhesive rubber tape on the RG58 would make it thick enough for the heat-shrink to "take". However, at present, I'm going to be using LMR400, so I shouldn't have a problem with that.

Well, if you use the cold shrink kits, like I linked to, it's an option, but I personally don't trust those very much.

The heat shrink is difficult to do outside since the breeze carries the heat away. Also, trying to do it up a tower with a long extension cord and a heat gun just isn't practical.

But if you are doing this on the ground, it's possible.

Usually good connectors, like Heliax or the Times Microwave LMR connectors, will come with a short length of marine grade heat shrink tubing to go over the back side of the connector where the cable enters. This helps seal it and provides strain relief.

I'm always leery of using things that weren't designed for the application (whatever that is). I did see a recommendation for a thin layer of dielectric grease on the threads, but I don't think I'd use Vaseline. I don't totally discount the experience of people who have been doing this longer than me, but I'd just rather use something that was designed for the job. Good to know about the Vaseline. I'll avoid it.

I'm always wary of the strange solutions that hams come up with. A lot of it is out of necessity due to lack of funds. Sometimes it's hams over thinking the issue (very common). Sometimes it's just bad advice. Unfortunately some of the bad advice gets repeated over and over again. You usually won't see these sorts of solutions used in industry for a very good reason. They just don't stand up to long term real world use.

As for dielectric grease on the threads, I'm not sure I'd do that. While there will still be some metal to metal contact, it's probably not a good long term solution, and something that could result in intermittent issues, especially if running higher power. Doing anything that makes for a flakey connection in the RF world is a great way to introduce passive intermodulation issues.