Re: Two layer primary

["Mark Fergerson" <mfergerson1-at-home-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Tesla list wrote:
> 
> Original poster: "Lau, Gary" <Gary.Lau-at-compaq-dot-com>
> 
> That's a fine idea on paper, but making a neat flat spiral out of 1/4"
> tubing is enough of a challenge.  Winding two turns per layer sounds like an
> invitation for frustration!!  I think I'm leaning towards gluing lexan
> spacer blocks to both sides of the insulating sheet of lexan.  I agree with
> the tuning inductor.

  My (loony) contribution; could a flat spiral be used for the
"bottom" layer and an inverse cone for the "top" layer? Joined at the
center, grounded at the outside of the flat coil, tapped at the
outside of the cone. Figuring the mutual inductance will be slightly
hairy (I'm pretty sure they won't just add algebraically), not to
mention the coupling to the secondary but mechanically it sounds good.
Better voltage isolation from bottom to top, anyway. Inside diameter
will have to be larger than normal because the inside turns are "hot",
though.

I can't draw ascii, but here goes (sideways view);

1     5
2    4
3   3
4  2
5-1

SSSSSSSSSSS

SSSSSSSSSSS

5 1
4  2
3   3
2    4
1     5
|     |
G     T

  Both layers' turns in the same direction, of course.

  Well, does it look worth the trouble? I've been considering this
already, and it's time I put it to the group for criticism.

  Mark L. Fergerson