Silicone on outdoor RF connections.

[Shockwave]

Is this an appropriate place to cry about blowing up the 180° phasing cable on your Yagi's T match? It turns out sealing the ends of this cable with silicone, was appropriate for 12 years, but not 13! Corrosion between the Silicon and the aluminum or copper metals, caused this seal to fail over time.

Once moisture got in, the Corona Arc turned the connection into a 0.1 ohm short. Silicone may not be the long-term solution for these applications. To make a long story short, I am now experimenting with a marine grade sealant by 3M called 5200. I'm told it already passes the microwave oven test, meaning it is a good insulator to RF.

 

[SuperLid]

Is this an appropriate place to cry about blowing up the 180° phasing cable on your Yagi's T match? It turns out sealing the ends of this cable with silicone, was appropriate for 12 years, but not 13! Corrosion between the Silicon and the aluminum or copper metals, caused this seal to fail over time.

Once moisture got in, the Corona Arc turned the connection into a 0.1 ohm short. Silicone may not be the long-term solution for these applications. To make a long story short, I am now experimenting with a marine grade sealant by 3M called 5200. I'm told it already passes the microwave oven test, meaning it is a good insulator to RF.

I wouldn't use it. In most cases, silicone (RTV), contains acetic acid. No bueno......I have been using DB Prods Vapor Wrap (butyl rubber mastic tape) for at least 40 years. Applied correctly, never a problem.

 

[Captain Kilowatt]

I have had silicone last for 20 years and counting. You MUST wrap the connector in a GOOD electrical tape first to avoid any corrosion that may occur from the solvents in the silicone as well as it makes it super simple to open the connection later. Just cut down thru the silicone/tape and peel it back. Nothing lasts forever but like I said, 20 years and still counting on some of my connections.

 

[Shockwave]

I have had silicone last for 20 years and counting. You MUST wrap the connector in a GOOD electrical tape first to avoid any corrosion that may occur from the solvents in the silicone as well as it makes it super simple to open the connection later. Just cut down thru the silicone/tape and peel it back. Nothing lasts forever but like I said, 20 years and still counting on some of my connections.

This particular phasing harness was made from LMR 600 and had no connectors on the ends. The ends passed through a grounded metal plate with with the braids bonded to that and the center conductor with its insulation extending to the other side to have both elements of the T match directly soldered to them.

The silicone was in contact with both the metal center conductor and the outside grounding, which left a prime location for corrosion to build between these metals. Not the smartest move on my part, especially with the RF voltages present here.