Re: Primaries and Copper Tubing

Subject:       Re: Primaries and Copper Tubing
       Date:   Thu, 24 Apr 1997 06:51:18 -0700
       From:   Bert Hickman <bert.hickman-at-aquila-dot-com>
Organization   Stoneridge Engineering
         To:   Tesla List <tesla-at-pupman-dot-com>

Dave and all,

Remember how nice, bright, and shiny your copper-tubing primary looked
when you first made it? Then it oxidized, to its normal, dull patina. 
If you bothered to silver plate it, the silver tarnishee and also looks
grungy after a while. BUT, suppose you gold-plated copper tubing, just
think how beautiful it would stay! A thin overcoat of gold should have
minimal effect on the effective resistance of the primary. For copper,
the "skin depth" at 100 kHz on a cylindrical conductor is a little over
.008". A 1 mil thick gold-plated layer will have negligible impact on
the effective electrical performance of the primary but would have a
dramtic impact on its long-term appearance. Might be a nice touch for a
museum coil...

BTW, because the gap losses so dominate the Q of the primary system,
even using aluminum tubing would have minimal impact on coil
performance. But you probably wouldn't want to use a carbon primary -
winding is a real pain - talk about work hardenning! :^)

Safe coilin' to you!

-- Bert --

Tesla List wrote:
> Subject:  Re: Primaries and Copper Tubing
>   Date:   Wed, 23 Apr 1997 11:27:22 -0500
>   From:   David Huffman <huffman-at-FNAL.GOV>
>     To:   Tesla List <tesla-at-pupman-dot-com>
> Gold is only slightly better than aluminum in resistivity. The one
> reason
> it is used in electronics is its resistance to corrosion. Silver is the
> best conductor ignoring superconductors. It would be pretty hard to beat
> good old copper tubing!
> In the primary isn't there a few ohms of resistance at the spark gap? In
> a
> series circuit the primary resistance seems to be a small part of the
> total.
> silver   p=1.59 microhm-cm
> copper   p=1.67 microhm-cm
> gold     p=2.35 microhm-cm
> aluminum p=2.65 microhm-cm
> iron     p=9.71 microhm-cm
> tungsten p=42.0 microhm-cm
> carbon   p=1375 microhm-cm
> ----------
<Original post re: Gold primary SNIPP'ed>