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14845Re: AW: AW: [SDRSharp] ebay antenna

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  • Ken Alexander
    Jun 24, 2014
      I stand corrected! Either the information I received was incorrect or I mis-remembered it! That's a word...isn't it? :-)

      73 - Ken



      > On Jun 24, 2014, at 8:27 PM, "jdow jdow@... [SDRSharp]" <SDRSharp@...> wrote:
      >
      > This prompted me to do a little research.
      >
      > Silver oxide is non-conductive except in certain forms such as used in silver
      > zinc batteries. It doesn't form easily.
      >
      > Silver sulfide is the usual surface film of tarnish seen most often. It, too,
      > is a non-conductor in bulk. In practical terms on relay contacts it increases
      > the contact resistance by a factor of about 3. So it's not bad but it's not
      > good either.
      >
      > Copper oxide and copper sulfide are less well behaved.
      >
      > In antennas you can actually end up with better performance over time with
      > anodized aluminum. It's surface doesn't conduct. So you have a very thin
      > layer of dielectric over the conducting aluminum. Add a nice layer of Krylon
      > sprayed over it all and the antenna will last a long time with little
      > change in performance over the years. You simply use a larger conductor to
      > make up for the poorer conductivity. (Krylon over silver or copper is not as
      > nicely behaved. I believe it may have sulfur in it. Many people use these
      > combinations anyway. So it may not be as bad as I suspect.)
      >
      > In constructing the antenna keep screws and bolts out of the electrical path
      > as much as possible. They are not as well behaved, either.
      >
      > And, yes, I mucked up in my memory about gold's conductivity. I for some
      > idiot reason thought it was further down than third place in the usual
      > scale (pre graphene).
      >
      > {^_^}
      >
      >> On 2014/06/24 14:38, Ken Alexander k.alexander@... [SDRSharp] wrote:
      >>
      >>
      >> Seems to me I read somewhere that one of the advantages of silver is that not
      >> only is it a good conductor, but the oxide (tarnish) coating that forms is an
      >> equally good conductor. I'm going from memory, so feel free to shoot down this
      >> assertion if you know better. *:) happy
      >>
      >> Gold of course doesn't oxidize. Another great reason it makes a good contact
      >> material.
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