Using Dielectric Grease to Weatherproof Coaxial Connectors

After reading various blog discussions on the use of dielectric greases for weather proofing protection of coaxial connectors, I have been motivated to post this information.

There is significant confusion out there on the use of dielectric grease fillers. We manufacture a Dielectric grease filler named ” STUF “ which is sold by Solid Signal. We will be blowing our own horn a bit but still providing some good information.
A bit long winded but bear with me.

What is a Dielectric ?
” Transmits electric force without conduction “

Dielectrics will not conduct electricity nor will they impede the transmission of electromagnetic waves. ( RF )

Often it is stated that using a dielectric grease on a coaxial or electrical connection will impede electrical throughput. If the dielectric is viscous, it will move out of the way of the electrical contact surfaces and occupy only space that were once occupied by air : A dielectric also.
Example: Common practice is to put grease (a dielectric) on car battery terminals. The grease is extruded away from the electrical contacting surfaces when re-assembling, allowing electrical throughput, while protecting the terminals from corrosion.

Filling a coaxial connector with a properly formulated dielectric grease is good weather protection practice and will not block electrical throughput or signal.

Most coaxial connectors will not contain much air space in the active cable core area when correctly assembled. Filling the connector with a dielectric grease with dielectric properties matching the cable core dielectric material (commonly foamed polyethylene) will not cause any significant measurable shift in connector impendence or VSWR and in some cases will improve it.

In cases where the cable core dielectric does not fit perfectly within the assembled connector; STUF will fill undesirable air spaces with matching dielectric material and improve impendence continuity and improve VSWR. ( See small picture below )

Incorrectly made f – connector on splice barrel cross section below: STUF filled air voids in ( RED )

If the center dielectric core is cut short of the inner face or the core does not fit tightly it will cause a irregularity in the transmission core with the added air space and cause return loss ( reflection ), poorer VSWR with the impedence shift.

Signal losses can be significant when caused by corrosion of the connectors internal components.

RF signal passes through coaxial cable and connectors in a way known as ” skin effect “. The bouncing electromagnetic wave uses the surface electrons of the metals to bounce off and move down the coax wave guide. Corrosion of these surfaces will hinder signal passage causing insertion (absorption) losses as well as return ( reflective ) losses. This situation is accelerated in powered coaxial systems ( AMP / LNB ) by moisture and electricity combining within the connector and causing acidic electrolysis. ( acid formation ).
Coax-seal, heat shrink tubing and tape wraps work great but are not perfect seals.
If there is a place for moisture to collect, it will eventually get there.


Note to Ham Buffs: In high power transmission, any moisture collection can cause arching within connectors. Comments have been received over years that filling connectors with STUF: Stops high power arching problems.

Over the years, ( Since 1993 ) STUF has been used and tested by many cable and broadcast companies for performance and only rejected once.
The company rejected the use of STUF on a -30 DB additional signal return loss from STUF connector filling (reflection). Decibel (DB) is a logarithmic scale which makes the -30 DB ( Down ) signal return amount = 1/1000 ( .001 ) reflection of the original signal.
Rarely will a coaxial system maintain that kind of performance simply due to aging of it’s components.

STUF is not a total do all for weather protection but adds an addition line of defense from mother nature.

Hope this information was useful, Welcome any comments,

Get STUF at Solid Signal! Coax Waterproof Filler (STUF) from Solid Signal