Re: Redesigning/tuning a coil

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Harold Weiss" <hweiss-at-new.rr-dot-com> 

Hi,


 > Original poster: pepperman-at-SoftHome-dot-net
 >
 > The current setup (all inch measurements are approximate):
 >
 > 15/60 NST
 >
 > Primary: about 19 turns of insulated wire, I'd guess around AWG 12
 > or 14, 18" diameter bundle

This primary might short out.  If you are replacing with Cu tubing make it a
flat spiral.


 > Secondary: 8.75" OD, 36.5" wound length, 1500-1550 turns of
 > AWG 22 varnished wire
 >
 > Topload: currently either a metal bowl upside-down over the top or
 > a 8" x 23" toroid of aluminum flex ducting
 >
 > main cap: 16.2 nF (6 caps in parallel, each 2.7 nF -at- 40 kV--the
 > doorknob type, probably ceramic)

I think this is right around resonant for the 15/60 NST.  Make sure you have
a safety gap that's properly set.  The Archives have a chart somewhere I
think, or try Terry's site.  Most ceramics have heating problems, but it
might get you by for now.  Think MMC.



 >
 > Spark gap: a single gap using several nails

At this voltage/current 3/8" carriage bolts will heat a bit and may not
quench well.  I take 1/2" threaded rod (chopped 8" carrage bolts) and round
the end that will be the gap.  From the gap I have at least 3" of threads,
which act as heat sink fins, helping keep the electrodes cool.  After a 1
min run, I can still hold the electrodes in my hand as they are warm but not
uncomfortably so.

 >
 > Ground: I'm not sure if he has a good ground--I don't think so

You are still at a power level where you can use electrical ground.  But a
good RF ground is best.  Keep your wires to it as short as possible, but of
convienant length.

David E Weiss