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Kote Against Rain

Members of the ISP-Wireless list discuss methods of waterproofing antennas. Many use a 3M product called Scotchkote, and others are working with teflon.

[May 28, 2001]

On the ISP-Wireless list in May, DT asked,

"What methods of waterproofing do most people use for antenna installations? I have seen two, both of which have the disadvantage that they have to be ripped off to remove.

One is electrical tape, covered with a modeling clay type compound, covered again with electrical tape. The other is heat shrink tubing with the ends taped and covered with 3M's Scotchkote waterproofing stuff. This seems to be a better seal, but requires AC power for the heat gun."

A number of respondents offered their favorite solutions:

[MS explained] "I use both electrical tape and heat shrink. When it's really windy or cold, I can't get a good seal on the heat shrink, but a butane torch helps."

[MC observed] "We use a layer of Scotchkote, a layer of self-vulcanizing tape, another layer of Scotchkote, another layer of self-vulcanizing tape, then one final coat of electrical tape. Haven't had to open one yet, with rain, freeze, snow, and hail tested so far. The only drawback is that you have to use a knife to remove it. It's time-consuming to do, but it's much cheaper than a service call."

[RH offered] "I use a form of mastic that I get from Electro-Comm, and I haven't had any trouble with tape coming off of it. I have tried using the glue-filled heat shrink only, and that does not seem to work for me. The glue sticks very well to the coax, but does not stick at all to the metal parts of the connector. So what I have been doing is a layer of tape, a layer of mastic, and a layer of heat shrink. This seems to work well."

A couple of others shared a more radical waterproofing method:

[JL noted] "I've been experimenting with a scheme that doesn't make a mess. I wrap the connector with several layers of ¾" Teflon pipe wrap. The most difficult part to completely cover is the transition between the coax cable and the metal connector. I then embalm it in electrical tape, mostly to keep it in place. The thin Teflon becomes an almost solid mass. I've only been doing this for about 18 months, but so far, so good."

[RH agreed] "It seems to me that the stuff seals water pipes, so it ought to seal coax. My version of the idea was to wrap it in Teflon tape and then cover it with heat shrink tubing just because I don't like trying to wrap coax with tape, especially when you're hanging off a tower in a 20 MPH wind."

RB warned that Teflon isn't the complete solution others might expect it to be:

"In the world of plumbing, Teflon tape is not a sealant. It is a thread lubricant. What Teflon tape does for you when wrapped around pipe threads is allow you to tighten up the pipe joint far more than you would have been able to with a simple metal-to-metal thread surface. I don't personally expect that it is that good of a sealant in this application, either.

But what it does do for you is keep all the wrap and adhesive from sticking so hard to the pieces and turning an otherwise reusable connector into a piece of trash."

—End

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