On Tue, 22 Mar 2011 13:06:04 -0700
"John Lyles" <jtml@losalamos.com> wrote:
> I'm pleased that Rob specified "in a HF tank circuit"
>for his comment "they are so nearly the same that copper
>strap is good enough; silver just looks pretty and
>impresses people."
Although for practical purposes on HF this is mostly true,
there is a difference. Copper oxide is an insulator while
silver oxide is a conductor. As the copper oxidizes, the
skin current encounters increased resistance and moves
deeper into the copper. At HF the difference will be very
small.
I have tested both bare copper and silver plated
inductors, trying to measure the difference in Q, and with
high RF currents (10 - 12A at 1.8 MHz) trying to measure
the heating difference. I could never tell between the
two. I have also tried to see if the Q of tarnished copper
inductors was lower, but again, the differences were not
measurable with my set-up. Still, I prefer silver plated
inductors. It must be the looks. (I have also tested
powdered-iron-core inductors. Even with silver plated wire
they had lower Q-s (200 - 250) and heated up
considerably.)
73, George, AA7JV
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