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Re: Topband: substandard quality F double females

To: <>, "Charles Bibb - K5ZK" <>
Subject: Re: Topband: substandard quality F double females
From: "Tom W8JI" <>
Reply-to: Tom W8JI <>
Date: Sat, 15 Dec 2012 21:37:56 -0500
List-post: <">>
Which brands/types are the "good" ones? Maybe some of mine need replacing...

BTW, I don't think I've ever met a "substandard double F female" or a substandard double D, for that matter. ;-)

Charles - K5ZK


I'm not sure which brands are bad, but I've been pretty lucky and not run into any. It doesn't surprise me, with Chinese manufacturing quality, that poor connectors are starting to appear. I think there is a risk people might go overboard on connectors based on a few substandard connectors.

I started dealing with F connectors back in the 1970's. I was systems engineer at a company that had many dozens or perhaps a hundred or so MATV and CATV systems. With hundreds of thousands of connectors, we could not tolerate even a small fraction of a percent connector failures.

All of the connectors we used, and I'm sure this applied throughout the industry, were tin contacts. The last thing we would use was gold, because gold would aggravate something we called "fretting corrosion" in contact with copper clad steel, tinned, or CCA cables. Tin plating was excellent under dry circuit conditions, like CATV drop feeds, where no significant current flowed through the contact.

Tin plated contacts had to be protected from oxidation by a grease. The grease also allows the connectors to be reused over and over without ruining the tin. We found a 100% pure silicon dielectric grease best. We used a product by GE back then, and I use something called automotive "tune up" grease now. It looks and smells identical. Outside of lightning I have no problems with hundreds of F connections in my system.

ALL connectors I have taken apart over the past 40 years have had spring contacts. This includes trunk cable connectors. The spring is a two piece deal that is sort of double V shaped from the side with one long leg. The wire pushes the V point's apart. A good connection requires a pretty good spring force. If you insert a piece of dry center conductor in the contact, you should be able to feel the female grabbing the wire. It can't feel like a zero insertion force connection, or you will have problems.

I would never use gold unless it was against gold. Tin is good for tin to tin, tin to silver, and tin to copper. I know of CATV systems that installed gold plated connectors and had to go out and remove them. I think Comcast got into that once. Besides that, some gold connectors are not even real gold. They are just gold colored "crap".

My suggestion is to ask advice from and use what the CATV industry uses and has used for years. I know everyone thinks gold is magic, but it can be a real headache even in cases where it really is gold.

The single most important thing in any connection is to NOT let a stray stand get loose and short the connector, to prep the ends properly including folding or not folding the shield as required by the cable and connector, and to lube the connector with something to keep air and moisture out.

I have many hundreds of F's in my system, and I'm not particularly choosey about picking certain brands of females so long as they pass the insertion force and pull test (they have to have a definite grabbing friction when dry) and are tinned center contacts. The last thing you will find around here are gold connectors, unless they mate to another gold contact. I also ALWAYS lube the connector with silicon dielectric compound.

73 Tom
Topband reflector -

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