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Moisture (water) in coax connectors!
I have been aligning my BUD and yesterday, I went to install my signal meter and in the coax lead at the base of my mount post. The first thing I noticed as the copper center lead was dark brown not shiny like it new anymore. New cable, only in service a couple weeks.
Then I noticed the normally white center insulator, down inside the connector was now black. I also noticed a trace of moisture)
I had put dielectric sealant in/on the connectors at the LNBs but since the cable run to the house was only temperary, I neglected to do those at the base. Being in WA we have had several inches of rain in the past week.
I'm no expert but I would have to conclude that the blackening on the insulation end was due to some RF arching. Just my guess and choice of terms.
I have now, cleaned the inside of the connectors with a Q-tip and used dielectric grease on all of them. Eventually, all of the outside connectors will be inside a weather proof closure.
I didn't notice any significient change in signal quality though.
If All Else Fails, Read and Head Instructions (warnings)
04-18-2009 12:19 PM
I've never used that dielectric stuff in a connector. Never trusted it. But other people seem to like it. I've used the black tar stuff on the outside, although it's so messy to take off, I've stopped doing that, and instead put the connectors in a plastic box.
Originally Posted by esteveW
But re the discoloration of the center conductor, I doubt that there was any "rf arcing" involved, however I would't be surprised if there might have been some electrolysis, either between the copper and some other metal in the connection, or involving dissolved metals in the moisture. I've had water pipes spring leaks simply by having a nail touch it.
It's voltage driven corrosion. Bad with solid copper cores, and terrible with copper coated steel cores. When running cable, try to think like water. If at all possible, route things so water runs AWAY from connectors and fittings. Ground blocks should be placed horizontially. Enclosures are a good thing, even though they can become a home for bees. Use generous drip loops at every connection, so if water does get in, you can cut off the 6-12" of corroded stuff without replacing the entire run. As for sealants, they work to a point, but are a mess to deal with when the time comes to change/troubleshoot things.
What you have noticed esteveW, is very common for my area South Fl,with our high humidty, an with our heavy rains. an any type of splice, ground block, out side will give a problem at some time in its life. the best thing is just not to have any coax connections out side, but if you do certain things will help with its life outdoors.
now the 1 bad that you said was mositure in the F-connector, the dia-electric materal is like a sponge it will suck an hold that water in, then will change the impeadence of you're coax, an have even seen where it will stop the voltage going to a lnb or drop it a bunch. the best way is to cut back a foot or 2 an redo it all, an seal it up good. an a good way to tell if you cut back far enough is strip the die-electric out of the coax what you cut back an squeeze it an pull at the same time to see if any mositure will come out of it.
now when you seen black inside the f-conector, thats carbon, from its burning, an if it goes on long enough it will burn the center stinger off. an Cadsufide described it very very well about "voltage driven" an the types of coax, that is why solid copper should always be used for a IF signal with voltage.
now these things that will prolong a splice out side.
1 Gell weather proof outdoor f-fittings.
2 Dia-electric grease (this will take up the extra air space in the fitting to what it ataches to reduce air to reduce the burn efect)
3 black sticky tape that B.J talk about, this is a very good sealent when aplied right.
4 if you're doing a ground block always make a loop below ground block to let water run down from it connection.
5 some kind of sheid or weather proof box, to keep spice out of the elements.
6 rubber ring (goes over treads on f-81 or ground block)
rubber boots over F-fitting don't use them here, have seen that they will hold mositure with our high humidty, use the rubber ring instead.
now for my area, doing all above will get more life out of a out door splice, but in time will still have a problem, you are only delaying invetable, I have seen splices that have not lasted a year due to not being proctive, an have seen others last for several years that have taken a lot of steps to prevent this from happening. an here a splice in the ground "forget it" it will always be a problem in years to come.
??? Burning??? I can't imagine why anything would be burning.
Originally Posted by 1captain
Seems to me like just plain electrolysis. Water doesn't conduct electricity very well at all unless metal salts are dissolved in it, and often what happens is metals like the copper get oxidized and go into solution, and other metals in the moisture get reduced and precipitate out. I'd guess that the black stuff is just a fine precipitate of metals and salts rather than carbon.
Whatever it is though, it's not good.
One thing that amazed me though, is that once I was curious about just how water-tight the F connectors were on the various components that were outside. Since I had a bad DiseqC switch, I decided to check that. Took the back off, and ran a wire in through where the center conductor goes, and it went clear into the interior of the switch. No attempt at all of water-proofing the things. There is no reason why they couldn't use connectors that are waterproof, except that they're probably saving a few cents per switch.
Moisture (water) in coax connectors!
I'm convinced the moisture (rain) got in through the threaded couplings. Some of them I have are the type with a flat on one side. Probably intended for use in electronics backplains. I have purchased some others now. The type of f connectors I use are the same as the Cable/Sat installers use. No crimping, just compression onto the cable end. They use a type with a water seal ring on the back end. I haven't found any of these but I do put sealant in that area. I'm thinking, maybe put a shrink sleeve on that area.
My present installation is only temperary since I haven't dug the trench for my conduit/cable run to the house. I will eventual put a weather proof box at the pole with my grounding connector. I think, at that time, I will rerun the cable going up to the LNBs since I don't think I have enough to cut back the effected section and still make a drip loop (plus some extra for future changes). I have plenty of single R6 Coax left over from an extensive Cable Co. job on my old house.
Thanks for all the comments and recomendations.
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