From: lfsheldon@gmail.com   
      
   On 7/7/2014 2:36 PM, Robert Heller wrote:   
      
   > I believe that copper is non-conductive.  And the phone wires are actually   
   > copper plated steel (for strength). Once the *thin* layer of copper oxizes,   
   > the *steel* wires no longer conduct well. And I guess the whole impedence   
   > rating of the *twisted pair* is blown away as well.  Hello massive signal   
   > loss, etc.  I also suspect that repeated exposure to water might wash away   
   the   
   > layer of copper oxide.  Plus as the cables move in the wind and the shething   
   > rubs against the copper wires, the copper oxide layer is rubbed off, exposing   
   > fresh copper.  It is not like we are talking about a solid bar of copper in a   
   > fixed unmoving location. Things are not that simple.   
      
   I believe this is nonsense.   
      
   I believe copper is the second most conductive (least resistive) metal   
   after silver and before gold.   
      
   http://eddy-current.com/conductivity-of-metals-sorted-by-resistivity/   
      
   The only "phone wires" made out of steel to the best of my knowledge is   
   aerial drop wire and the twisted stuff the Army used to use in the   
   field. There are probably a few other special applications where the   
   wire has to support its own weight (which copper is NOT very good   
   at--which is why aerial cable is always hanging from a steel messenger.   
      
   Somebody can check up on me, but I think exchange cable was 24 gauge   
   (0.02 inch) while toll cable was mostly 22 gauge (I say "mostly" because   
   it sticks in my mind that there were things like PGCUs on 20 or even 18   
   gauge wire).  If I run across my "Green Brain" I'll check.   
      
   The copper wires inside the cable can't "rub against the sheath"--it is   
   insulated and bundles of pairs are wrapped.  The cable is supported by   
   the messenger and there is not a lot of local movement--the whole span   
   may sway a little but where needed, sway breaker minimize the motion--I   
   never heard of a cable failure due to motion.   
      
   The old lead sheaths would crack from the small amount of motion, and   
   the old rings they used to use would wear holes in the sheath, but so   
   far as I know the major causes of sheath failure were squirrels and insects.   
      
   And those holes were a problem, because the insulation around the wires   
   was paper and wet paper has some poor-for-the-task electrical properties.   
      
      
   I don't think copper oxide (in either cupric or cuprous form) is water   
   soluble, but cuprous oxide does make, if I remember correctly, a fine   
   rectifier and might be the first "semiconductor" identified, but not as   
   a desirable property in cables.   
      
      
   The rest of the article here is probably too silly to even bother reading.   
      
   --   
   Idioten aangeboden. Gratis af te halen.   
   h/t Dagelijkse Standaard   
      
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