Filling Coaxial Connectors with Dielectric Grease for Weather protection

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by CROSSDEVICES, Jan 17, 2014.

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    Note on Use of Dielectric Greases:
    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. A bit long winded but bear with me.

    There is significant confusion out there on the use of dielectric grease fillers. We manufacture a dielectric grease filler named " STUF" and will be blowing our own horn a bit but still providing some good information.

    http:// : What is a Dielectric ? ( Background )

    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.

    http:// : What is STUF and why use it?

    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: 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.

    Here is my link to my information page on the use of STUF filler for weather protecting coax connectors :
    Includes other " techie" info on dielectrics as well:


    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,

    David Cross / CROSS DEVICES :
  2. KM5FL

    KM5FL Ham Member QRZ Page

    I have used your product in the past. Good information, but none of your links work.. As my supply of STUF was long ago depleted, could you PM me with your contact information and/or the names of dealers??

  3. KB0TJ

    KB0TJ Ham Member QRZ Page

    Just use to get the website up... there are lots of links on the page to get to the "Stuff". HI

  4. KB4QAA

    KB4QAA XML Subscriber QRZ Page

    Nice to hear from a manufacturer! Thanks for the info. bill
  5. AE5JU

    AE5JU Ham Member QRZ Page

    David, I had done a guest blog post on this subject at K9ZW's "With Varying Frequency".

    I even mentioned your product, Stuf.

    I am an absolute believer in using dielectric grease for weatherproofing. Just like "gel-filled" coax and CAT-5, if silicone grease fills the empty spaces, then water cannot get in if there is no place for it to go. I used to take my antenna down once a year and unwrap, clean, check, and redo the coax connection. Each time I found it clean and free of corrosion. Now I am going to a two year schedule.

    Silicone grease alone is not enough, but as you said, "an additional line of defense."

    Paul - AE5JU
  6. W0AAT

    W0AAT XML Subscriber QRZ Page

    Wish "stuf" was available in a larger package, working on a connector block design for some homebrew antennas and need a lot of something to fill them.


    Nice video, Folks need to see real documentation.
    Just a note on silicone greases.
    They are the best oxygen / oxydation blocker you can get and has a "ZERO" moisture absorbtion factor.
    You have to get it off your hands though, which takes about a week.
    Puts the wife off limits for a while.

    When you get up above a Gig, expecially on RG-6 size cable which it was not designed: The mode of RF in the cable really starts packing up and losses, leaks and reflections can happen real easily with any dicontinuities in the cable. F- Barrell splice connectors have a large internal hole on the inside where the center pincher contacts lie and filling this with a dense grease is where problems with signal throughput are measurable.
    So on larger diameter cables and lower frequency, silicone grease can be fine except:
    We never used it because it being a non-petroleum product, it is imcompatable with PVC, Vinyl, ABS etc plastics and over time ( couple years ) it will migrate plasticizers that keep the outer cable soft. I do not know about this occuring on rubbers.. Have to look that one up.
    When you put in the grease and tighted the connector it is forced nicely back into the ferrile braid area and waterproofs it nicely but gets into the braid and onto the area where the connector is pinched or crimped to the connector. This is where it can harden and crack.
    I would like to know if the long term tested Silicone filled connectors in your video test were brittle in that area just behind the ferrile. Would be interesting to know.
    All cables have a terminal life, Silicone grease will definately keep call backs off for quite awhile.
  8. KB1NXE

    KB1NXE Platinum Subscriber Platinum Subscriber QRZ Page

    I've used Stuf for years. Only complaint I have is it's a pain to clean if you wish to reuse the connector.
  9. AE5JU

    AE5JU Ham Member QRZ Page

    David, up to last year, I have been redressing the connection every year. Each time the grease looked new. The butyl rubber tape (Scotch 130C) was fully bonded into a solid rubber "boot" over the connection, and bonded to the coax, too. The Scotch 77 electrical tape looked fine, still adhering well. Just as in the photos, I had to slice off the 130C mass. The rest wiped off neatly. An aside... in the photos see how clean and shiny the PL-259? That is a silver plated connector, but no sign of turning black.

    It's been about a year since the last redressing, but I've gone to a 2 year cycle on this. It will be a year before I could report back.

    Paul - AE5JU
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