I have two coax cables that need to splice together. I am using waterproof F-type connectors but I was wondering if a dielectric grease where the two screw in to each other would be harmful (signal issues, .etc.).

This is the product: https://www.homedepot.com/p/CRC-3-3-oz-Technician-Grade-Dielectric-Grease-05113/206843029

3 Answers 3


Living and working as a cable television technician in a beachside region, I can attest to the value of the silicone dielectric grease for improving the lifespan of these connections. Salt air eats everything in time, yet the grease prevented corrosion after five years. The fittings were assembled with "boots," rubber covers which resemble spark plug wiring ends. The grease was applied liberally, inside and out, and the boots then slid over the fittings.

Sun, salt, sand and wind would eventually deteriorate the rubber, but even then, the fitting within the mass of grease held up quite well.

  • I have used dielectric grease on head end installs as required by the manufacturer. These units were tested and the impedance of the wire/ connection was not affected. After that I used dielectric grease on all my exterior fittings.+
    – Ed Beal
    Dec 18, 2018 at 14:18
  • Thank you for your sage advice. Indeed this house is right on the inter-coastal so salt air is a concern. Could I use heat shrink as "boots"?
    – Alex
    Dec 19, 2018 at 3:18
  • We didn't use heat shrink because the fittings have to be accessible after the installation. From a user reference, as long as you don't overheat the fitting, it should work well enough.
    – fred_dot_u
    Dec 19, 2018 at 12:41

I have never used it and am not familiar with the ingredients of that product but generally where RF is concerned you do not want to add something that was not already called for in its application. You said the connectors are water-resistant (water proof is hard but not impossible).

Adding anything at all will introduce performance changes and not for the better (i.e., its not going to boost the signal without active components), it will likely add some filter/tuning impacts but not something you can really control and again, not for the better.

Why add it? Is there a different problem you are trying to solve? If you are aiming for an anti-sieze application, it could work, just read the product label to ensure it doesn't react with the coating or metals used on the connectors and barrels you are using. Use it sparingly on the outer female threads only. Pay mind to avoid the center conductor and the insulator between the threads and the center. Also avoid the very first thread to avoid sandwiching it into the insulator or center connector when tightening it.


Consider STUF dielectric filler, Made for coax, Saw a new video on it : https://www.youtube.com/watch?v=2l0PqZr8-_o

There's footage of a coax male end packed with the filler which is white in color. The claim in the video is

Prevents moisture infiltration by occupation

The packaging reads

Dielectric water proofing filler: for coaxial connections. With Teflon.

The company website links to www.crossdevices.com and coax does seem to be a specific and focused application of theirs.

STUF is actually an acronym

Silica Teflon Unionizing Filler

They claim to match the dielectric constant and impedance matching to the polyethelyne insulating foam surrounding the conductor.

  • Hi and welcome to Stack Exchange. Your answer has been flagged as a low quality submission. You should edit this to make it more self contained instead of linking off site to some unknown uTube video. In particular if you have experience with some product or can accurately describe its use and applicability to the question please do so and eliminate the link. If not this could get deleted for not being up to site standards.
    – Michael Karas
    Mar 9, 2019 at 9:36

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