----- Original Message -----
From: "LA5HE Ragnar Otterstad" <la5he@otterstad.dk>
To: <topband@contesting.com>
Sent: Wednesday, November 21, 2007 3:53 AM
Subject: Re: Topband: Silver Plated Conductor
> GEORGE WALLNER wrote:
>
>>Would silver plating the conductors make a practical
>>difference? There is no significant heating of the
>>conductors now with full legal power.
>>
>
> Before you consider silver plating a coil, here is something you should
> know. At 2 MHz the RF skin depth in silver is 0.00178 inches. You need
> about three skin depths of plating, that's about 0.0053 inches. If you
> just walk into a plating shop and say, here silver plate this, you will
> get about 0.00002 inches. "Highly polish-able" grade silver plating is
> 0.001 inches and costly. You need 5 times that. It's going to be
> expensive. Most ham coils used at low frequencies are silver plated
> just for appearance purposes.-
>
> ---------------------------
>
> In marine transmitters all coils I have seen were silverplated. My
> understand is that
> 2-3 mikron was used, whatever that is in medival terms.
> 73 Rag LA5HE
>
>
80 to 120 microinches in "medieval" terms, Rag. Silver oxide is a pretty
good conductor whereas copper oxide is not. Not sure what if any Q
change is associated with a pristine bare copper HF coil vs an oxidized
one vs the equivalent pristine silver plate vs oxidized silver plate. It
would be an interesting experiment, but my guess is that the difference
is not significant at HF.
In any case, as long as his coil isn't getting very warm at 1500 watts,
then George should be in fine a shape regardless of the plating.
Remember 50 watts is a lot of heat to dump into even a large coil, but
still only 0.15dB of loss out of 1500 watts input. All-in-all laying more
radials (assuming a vertical) would probably pay more dividends per
unit effort expended in terms of improving signal strength than
squeezing the last 0.2dB out of the matching network.
Happy Thanksgiving, All.
73, Mike W4EF
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