Let's take this all into the perspective of the real world
.Many things interact to determine coil Q, but among all of
them the plating or tarnish on the wire surface seems to be
one of the least important factors. When the surface becomes
more resistive the current simply moves deeper into the
wire. The only real danger is if the wire is stranded or
woven, in which case corrosion or tarnish can greatly reduce
performance.
Several years ago I left a detuning coil made from 30 or 40
turns of silver plated #14 copper wire laying on the ground
at the base of my 300 ft tower. I retreived it a few
minutes ago. It has tower paint, dirt, grass, and lots of
silver oxide all over it. It even has been sprayed with
Roundup several times.
I measured it on a HP4191 impedance test set, the common
industry standard instrument for measurements of this type.
>From 2-4 MHz it read ~40uH with a Q of 200. Knocking off the
loose grass and dirt increased Q to about 220.
A shiny new coil of this construction that has been wrapped
in " silver saver" paper measures just over 300.
A few lead/tin (solder) plated air dux coils that are a bit
tarnished measure nearly the same as the coil that is silver
plated and shiny. They are all around Q= 250-300.
I can have a Q of ~500 with number 8 tinned buss wire, and
about the same if it is silver plated. Bare copper is about
the same, clean or tarnished
A large edge wound or copper tubing coil measures in the 800
range, and ~1000 is about the upper limit of any HF coil I
have measured. Leave them outside, bring them back in, and
they are about the same.
So, why all the worry? Are we going to a coil show?
73 Tom
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