Hi Andy,
I can see no reason why it could be so. Frankly I don’t believe it. Perhaps it is the definition of “better” but I can’t imagine wht that might be so let me explain why I disagree.
A quick look at a text book will show you that the rf resistance is inversely proportional to the skin depth and directly proportional to the resistivity of the material. For plated surfaces it depends on the relative thickness of the plating layer, the skin depths and material resistivities. The plating does not create magic.
The skin depth in silver at 10 MHz is 20 um and for copper at 10 MHz it is 21 um. Silver has about 5% less resistivity than copper. So using silver wire instead of copper wire makes little difference to the rf resistance.
Now for the plated copper wire.
If the silver plating is equal to three times the skin depth then very little current (< 5%) will flow in the copper. The rf resistance will be almost the same as silver alone.
If the plating is less than 1/3 the skin depth then a substantial amount of the rf will flow in the copper. The rf resistance will be less than for copper alone but noticeably greater than for all silver. The differences are however all small.
The elephant in the room is that typically the plating is 1 to 2 micrometers thick which is 5 to 10% of the skin depth at 10 MHz. So most of the rf flows in the copper anyway! the rf resistance is almost unchanged!
There is no significant gain in rf performance for good copper wire whether you plate it with silver or not.
So why plate copper? Silver oxide is a much better conductor than copper oxide. So if the conductor cannot be kept with a clean shiny surface, silver plating will give good rf conductivity even when tarnished. Oxidised copper also makes good rectifiers.
Gold is more resistant to tarnishing but the plating process may give the gold plate a resistivity greater than copper. The lack of tarnishing is often worth the slightly higher loss and higher cost…
If you are silver or gold plating steel then you need to have the plating three times the skin depth (60 micrometer at 10 MHz) as steel is not a particularly good conductor and its permeability creates a very small intrinsic skin depth making it horrid at rf. It’s rubbish even at 50 Hz.
73
Ron
VK3AFW
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