Topband: ground radials & conductivity
k1fz at myfairpoint.net
Mon Dec 15 11:14:56 EST 2014
In Broadcasting, we used silver plating of tuned circuits often as copper oxide, depending upon the degree of oxidation, is a poor conductor,
Silver oxide is a much better conductor than copper oxide.
In the High powered short wave station that I worked. the ABB Swiss made transmitter plate tuning inductor was made of oxygen free copper, and water cooled. We used deionization resin beads to keep the water in good shape. One time as the water quality dropped we noted a shift in tuning that was traced to the water cooled Comet vacuum variable capacitors. Copper oxide, in the water, was causing a change in capatance. With Testing & research we found that copper oxide has stages of conductivity the last, black in color, is close to an insulator, that may act as a dielectric.
Ground radials can suffer varying degree of copper oxidation depending, upon soil, electrolysis, and other factors.
Covered wires can eventually have water intrusion. In the 1990's I used enameled coated wires, that have worked well so far.
Electrical and thermal conductivity have a QUITE similar order of published metals.
Electrical conductivity of metals http://eddy-current.com/conductivity-of-metals-sorted-by-resistivity/
Thermal conductivity of metals http://en.wikipedia.org/wiki/Copper_in_heat_exchangers
Note: The backstay we found of the old 1920's Belfast radio station was galvanized iron. The galvanized surface was in good condition after so many years in the ground)
In the aging process have wondered how Zinc oxide compared with copper oxide. (Copper-weld vs zinc coated electric fence wire) Zinc is not nearly as good to start with.
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