Pri/Sec spacing

Subject: Pri/Sec spacing
  Date:  Fri, 6 Jun 97 08:55:39 EDT
  From:  Gary Lau 06-Jun-1997 0838 <lau-at-hdecad.ENET.dec-dot-com>
    To:  tesla-at-pupman-dot-com
    CC:  lau-at-hdecad.ENET.dec-dot-com

Matt McArthur (RSNV02D-at-prodigy-dot-com) raises a question that I also was 
wondering about:

>...  The best guess I have to the wimpy sparks is bad coupling. The
>secondary sits about one inch from the BOTTOM of the primary.  I had
>just read a post that said something about the secondary for lower
>powered coils being 1 1/2" ABOVE the primary to enhance the coupling.
>  Could somebody please put me back on track!?!?!?

I myself am still working on my first coil and was planning on
mounting a flat 1/4" tubing primary BELOW a 1/4" x 2' x 2' sheet
of plexiglass, and mounting the secondary above the sheet.  This
would seem to afford some good protection against primary strikes
and at the same time, make primary tap adjustment very
accessable.  As I am now preparing to start on my secondary
(4.25" x 20"), I'm wondering how close to the end to start my
winding, and whether I might not be able to get the secondary
close enough to the primary using this geometry.

What kinds of pri/sec spacings to other folks use?  If the
closest I need to come is 1 1/2", then I should have no problem.
If it matters, I'm planning on using a pair of OBIT's to power

Gary Lau
Waltham, MA