Technical Mentoring and Elmering Net – 10/5/2017

The audio archive of this net can best be followed by downloading the .mp3 file for the appropriate date here and listening with the media player of your choice. You can move the progress slider forward or backward to the subject of interest to you.

We had another good net tonight with 10 check-ins plus net control, Brian, K6BPM and some chat room visitors! Tonight’s subjects included:

  • K5CAW asks K6FLD if he’s received his Raspberry Pi Zero W yet and the cost savings between it paired with the ZUMspot and the Shark RF openSPOT.
  • Why do so many manufacturers use silver to coat contacts and won’t it tarnish?
  • What should we use to coat radomes?
  • Why do we use PL tones in the US and Europe uses Tone Bursts?

Tune in to the SBARC TM&E Net every Thursday at 8:00 PM local (2000 Hrs) and see what interesting questions will arise or ask some of your own! All club members and visitors are encouraged to check in to the net each week and join in with questions and /or answers to and contribute the knowledge of new and seasoned amateur radio operators alike.

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2 Responses to Technical Mentoring and Elmering Net – 10/5/2017

  1. w6eww6ew says:

    I looked up silver tarnish today. It turns out it is Ag2S, formed from the reaction of silver with H2S (hydrogen sulfide) in the air.

    I called Amphenol after looking on line at several brands of connectors. Various models of their Pl259 (plug) and SO 239 (socket) connectors have silver plating in the center conductor contacts, but most now use nickel plating on the outer conductor parts of the connector. Which is why the outer conductors do not seem to corrode as some did fifty years ago when the whole thing was sometimes silver plated brass.

    All parts are plated after fully formed and machined, e.g. the threads.

  2. w6eww6ew says:

    Not sure what happened to my previous comment.

    To recap… Silver tarnish is Ag2S, silver sulfide.

    Amphenol tells me that they make their PL 259 connectors out of brass, usually with silver plating on the center connector and nickel plating on the body of the connector — the outer conductor.

    The tech didn’t know why tarnishing was not a problem. I speculate that: 1) the layer of sulfide in tarnish is very thin, protecting the underlying silver from further sulfidization; 2) silver sulfide IS conducting, albeit with a degree of resistance, but if the path is very short through a thin layer, the resistance may be negligible; 3) when the surfaces of the plug and socket are touching, there is virtually no space into which hydrogen sulfide can intrude, forestalling further significant tarnishing.

    The amount of H2S in the air is very small, and tarnishing of silver takes weeks or months in any case. When protected inside the socket with plug screwed in and the center conductor contacts touching, tarnishing is unlikely to occur. The outer body of the connectors is plated with nickel, not silver.

    In RF applications, even if there were a thin layer of tarnish on the center contacts, they would pass RF like a capacitor.

    That’s the best I can do without asking to talk to the Amphenol engineering department. — Doc

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