Filling Coaxial Connectors with Dielectric Grease for Weather Protection

Discussion in 'Free To Air (FTA) Discussion' started by crossdevices, Jan 17, 2014.

  1. crossdevices

    crossdevices Thread Starter New Member

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    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


    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.
    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.

    " STUF PREVENTS MOISTURE INFILTRATION BY OCCUPATION" SINCE 1993

    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: crossdevices.com/cross devices 002.htm


    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
     
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  2. Lone Gunman

    Lone Gunman Well-Known SatelliteGuys Member

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    The "STUFF" I use comes in a jar with the words "Petrolieum Jelly" on the label. I've used it since back in 2000 when I moved my dish to this new house and haven't had a moisture or corrosion problem since. And did I mention that it's cheap? I'll bet that most homes already have a jar of it in their bathroom cabinet? ;)
     
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  3. Titanium

    Titanium SatelliteGuys Family
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    A potential problem with petroleum jelly is that it will liquefy when it gets hot. I remember making a big mess once in my distributor. Couldn't find the tube of dielectric silicone so put a dab of Vasoline on the points. Never did that again!
     
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  4. harshness

    harshness SatelliteGuys Family

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    While petroleum jelly gets along well with PVC and synthetic rubbers used in conventional electrical connections, it isn't particularly compatible with LDPE used in cheap-ass coax. I've not seen any testing on gas injected HDPE.

    Having air as a dielectric may well be how the connectors were designed and to replace it with a material that has different dielectric properties may not be ideal.

    I've also seen some cautions against not applying the grease before making the connection as it may prevent the mating surfaces from scraping their way through oxidation (or oxidation preventative coatings) on the surface of the metal.
     
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  5. jorgek

    jorgek SatelliteGuys Family

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    Well in my 25 years in the land mobile radio industry no one ever promoted or used any kind of goop in rf connector either in vehicles, base stations or 500 foot tower installations. What was used to seal connectors was a commercial grade of coax seal. As well as a ham radio operator and FTA hobbyiest never had any issues with properly installed connectors indoors or outdoors.

    Did that promotor of "Stuf" pay for that ad in post #1?
     
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  6. Cham

    Cham Professional Hobbyist
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    I have always used high voltage sealant used in ignition systems etc. As the OP stated the idea is to displace the air to minimize corrosion to contacts and conductor surfaces. It's likely saved me a few trips up tall towers that I would prefer not to be on top of...or fall off of... I am sure "Stuf" is just fine, and there are lots of similar products.
     
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  7. turbosat

    turbosat SatelliteGuys Family

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    Interesting information. But I'm afraid it will be another case of "Should I ground my satellite dish or not" debates. I never have tried the dielectric grease but it couldn't cost much to see what happens. Spring will be around again before long and I'm sure there will be some connectors to replace here. I agree, that no matter how much coax seal you mold onto a fitting, moisture eventually gets in from the outside.
     
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  8. Lone Gunman

    Lone Gunman Well-Known SatelliteGuys Member

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    Humm, I don't think I'd use it in a distributor either as those things will get plenty hot enough to make the stuff run off. That and the lubricating qualities aren't that good either. I doubt you'd ever see a coax connection exposed to 180* though, which is what most engines with point ignition operated at back in the day.
     
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  9. Stargazer

    Stargazer Supporting Founder
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    What we used in the wireless internet industry was black coax seal tape. One type would stretch around the connector while the other type changed shape like play dough. I assume that would work on satellite coax rg-6. There was a certain way to wrap it to where the overlap goes down so that the water would not run in the gaps. I seen something similar for wrapping plumbing drain pipes.
     
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  10. trinidex

    trinidex Active SatelliteGuys Member

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    Amalgamating tape - you apply it 'backwards' with the adhesive side facing out, it then amalgamates into a doughy lump providing protection from the elements.
     
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  11. Stargazer

    Stargazer Supporting Founder
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  12. Titanium

    Titanium SatelliteGuys Family
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    Petroleum Jelly melted on my lips as a kid. My mom would try to keep me from getting chapped lips... and I wasn't that hot!!! LOL!!! ;)
     
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  13. stardust3

    stardust3 SatelliteGuys Family
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    Wrench tightened fittings & a weather boot filled with grease over the outside is a good defense against moisture. Was never crazy about applying it directly to a center conductor.

    Also this should go without saying but worth mentioning. Cable should be routed as such so water runs away from the connector, not towards it.

    Eventually most non flooded coax will break down & absorb moisture like a sponge. From my cable days have seen many overhead drops that once a connector was cut off at the house would drip water out like a leaky faucet that wouldn't quit. Replacement is the only fix at that point.
     
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  14. stardust3

    stardust3 SatelliteGuys Family
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  15. turbosat

    turbosat SatelliteGuys Family

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    EXACTLY> I disconnected a line from my newest scanner antenna on my tower a couple of weeks back, noticed the discoloration on the center conductor , then let the cable flop down, about 3 feet fell down from the next cable tie. That thing RAN water like a garden hose, I was astounded, never saw that before. It'd been up about 2months and was wrapped good with coax-seal, with (what I thought) was a good drip loop too.
     
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  16. crossdevices

    crossdevices Thread Starter New Member

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    Just a note on Silicone Grease.
    Silicone is the best oxydation blocker out there and has ZERO moisture absorbtion.
    It does carry the Insertion loss problems when you get above a GIG on smaller diameter cables as with any dense filler.
    So weatherproofing with it on a general use in most cases is easy, works well but will keep the wife away from you for about the week it takes you to get it off your hands.
    There is one thing that kept us from putting in the mix: Silicone is not a pretroleum product like most of the plastics used for the cable overcoat : PVC, Vinyl, Abs etc. Over time ( +/- couple years ) It will migrate the plasticizers that keep it soft. This will be seen right on the back edge where the ferrile meets the cable (crimp edge ). " Crack " It gets on the cable outer covering through the inside when it's assembled and tightened. I do not know if it is the same for rubber overcoats; Have to look tht one up.
    Overall it will weatherproof easily and for general use will keep thing shiney inside the connectors.
    David
     
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  17. Stargazer

    Stargazer Supporting Founder
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    I have seen ethernet wire running down a tower into the power box siphon water all the water down even with a drip loop. Once it gets a crack you got problems. Have to replace the whole cable. We have used some ethernet wire that had silicone made right in it and we never had any issues with it. I believe the phone companies use silicone in their multiple pairs of wire as well.
     
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  18. waylew

    waylew Well-Known SatelliteGuys Member

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    Go in to work one nite to turn things on and get ready for that nites show,used to work at a drive-in.Anyway,walk in to the projection booth to turn on some breakers and there's water dripping out of the breaker panel,WTF!
    Take the cover off the panel and see water dripping out of an mc cable,pulled the cable out of the panel,mopped up the puddle in the bottom,then put a big fan blowing right on the panel and got it dried out.The show went on.:popcorn
    Next day investigated,the cable ran out to a security light,the end of the cable pointing straight up,and a lump of dumdum putty laying on the roof.There had been a pretty good t storm the day before and the water just ran down inside the metal shield and exited in the panel.
    Gave the boss hell for his half assed install job,(was done before I worked there) and went about my business.Some of the things I found in that place make me wonder how it's still there.:eek:
     
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  19. RT-Cat

    RT-Cat "My person-well trained"
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    .
    I use some gray stuff that looks like molding clay. Acts like it also. Wraps around connectors, easy to shape, stays in place, does not melt, does the job. If it has not been outside for too long can even be reused. Easy to remove and does not leave a "mess." Works well. Never took a connector apart and found corrosion or any water.
    l
    waylew,
    Interesting info on your projectionist days. Did that in a drive-in in Summer of '69, then went to a weekend theater for 5 years. Sure did like the dusk to dawn shows. Surprised yours is still there. My drive-in has been replaced by a Shell station, McDonald's, and a car wash. I sure would like to see the modern digital equipment of today.
     
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  20. Tron

    Tron SatelliteGuys Family

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    I got started with film and video in the projection booth. Nice to see folks here with the same experiences. Projection booths are usually all digital these days, with hard drive arrays taking the place of platters and digital ultra-def projectors replacing 35mm. Some shows even come in via satellite. Theatrical projection booths now resemble television station master control rooms.

    Sorry for going off topic, now back to our regularly scheduled topic :) ...
     
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