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Re: Coupling constant for 4.25" secondary
Are there problems from edge wound copper strap regarding spark break
out from the sharp edges? Is there an optimum spacing between turns to
get maximum resonance without sparking? Would insulation assist or hurt?
Are there local suppliers of copper strapping (my hardware stores only
have the strapping to support pipes-copper plumbers tape).
Thanks, Bob Volk
> >With small coils systems the best way to achieve a high coeff of coupling
> >(0.18 to 0.20) is to use edge wound copper strap which allows for a very
> >high density as opposed to copper tubing or wire. We usually hit 0.18 with
> >our smaller systems and this is with a flat spiral configuration using
> >edgewound copper strap --- usually 5/8 inch wide. It works for us.
> >
> >Regards,
> >Dr.Resonance-at-next-wave-dot-net
>
> Hi Dr. Resonance
>
> Thanks for the tip. This was something I was wondering about - primary
> geometry vs coupling. A while back, there was a brief thread about using
> two-layer primaries. It sounds like both the edge-wound and two layer
> techniques achieve the same thing - concentrating the primary in a
> smaller volume, and presumably, that achieves a higher k. I assume that
> some kind of insulation is necessary between strap turns, and that
> varying the tap point is somewhat less straightforward than with tubing.
> I may opt for the two-layer approach (since I don't have a source of
> copper ribbon), and I'll probably make a dry run using just some 22AWG
> wire to test the inductance and k before building the real thing. I
> assume wire gauge won't affect L and k if the spacing is like the final
> version. It may be a while before I get to this, but I'd be interested
> if anyone has pictures on-line of either ribbon or two-layer primaries.
>
> Regards,
> Gary Lau
> Waltham, MA USA