On 10/ 4/10 12:42 PM, LB3HC wrote:
> I am working on some loss estimates for the tank circuit of my GS35B
> amp. design and I am considering if silver plating of the tank circuit
> coil is feasible or not. I intend to use copper tubing intended for
> camping gas installations in the tank coil(s), as it is readily
> available. According to VE1ALQ's tool, the 3 times skin depth for RF
> current on 10 meters wavelength is 36 Microns. Silver plating kits
> that are available on the market** typically states a plating
> thickness of 70 micro inches, which is only 1,7 microns. This is 1/20
> of what is necessary to have silver down to the 3 x skin depth, if my
> calculations are correct.
>
> What are your experiences with silver coated contra non coated tank coils?
>
> Polishing the copper tubing will reduce the RF skin current resistance
> according to some sources. Is this true, and in case it is, what are
> the mechanisms that makes polished copper conduct better (RF) than non
> polished copper?
>
> **
> http://www.cool-amp.com/product%20info/COOL-AMP%20One-page%20Info%20Sheet%20&%20inserts%20%28FINAL%2004.30.09%29.pdf
>
> 73
> LB3HC
I don't know the depth, but I know I had a 2 m anode line silver plated for a
dual 4CX250B amplifier. Careful measurements before and after plating showed no
statistically significant difference. The line was brass, which is a poorer
conductor than copper, so the difference between brass+silver should have been
better than between copper+silver. But it was a waste of time - other than it
looked nicer!
A friend got the plating done free, and I know it was deeper than normally
done,
though I can't recall the depth.
You really are wasting your time at 10 m if you think you will improve
efficiency. Anybody that tells you that it made a difference at that frequency
is kidding themselves.
If anything, gold plating would be more useful, as it would stop oxidation. In
which case, you need only a very thin coat - forget about skin depth. 99% of
the
current will be in the copper, not in the gold, but the gold will stop
oxidization.
Oxidization might be one of the advantages of cleaning the copper, but I don't
really think it will make much difference until you reach a few GHz.
I was once told silver oxide is a conductor and copper oxide is not, so that's
an advantages in using silver. I've never looked in the professional literature
to see if that is true - it may be a lot of rubbish.
dave
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