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Re: 120 watts 3"


From: 	Esondrmn-at-aol-dot-com[SMTP:Esondrmn-at-aol-dot-com]
Sent: 	Wednesday, November 26, 1997 7:22 AM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: 120 watts 3"

In a message dated 97-11-26 06:26:08 EST, you write:

<< I have been experementing with my smallest Tesla Coil.  It is 120 watts,
6K
 >volts, 20 ma.  The secondary is 1.5" PVC pipe 6" long wound with #24 wire.
 >The primary is 5 turns of #12 copper house wire with vinyl insulation close
 >helix wound 3" diameter.  RQ gap .025 x 4. The output spark at the toroid
is
 >3.125" with a .0014 uf cap and a 2" doorknob as the toroid.  If I change
the
 >primary coil from 5 turns to 6 turns or to 4 turns I am off resonance
 >frequency and the discharge spark gets shorter as expected about 1" long.
 >If I change the toroid to a 6" diameter copper sphere or no toriod at all I
 >still get a 3" discharge spark?  If I change the cap from .0014 to .0017
 >or.0034 or .005 or .0064 or .01 uf I still get a 3" discharge spark?  Some
 >of these changes makes the discharge spark get hotter or less hot but the
3"
 >spark length does not change. I know the
 >discharge spark will change if I change the number of turns of the primary
 >but why won't it change when I change the cap or toroid?  Is it because it
 >has a wide bandwidth and I haven't made a large enough change in the caps
or
 >toroid to make any difference?  humm.
 >
 >Gary
 > >>
Gary,

I would suggest the coil is not in tune.  I did some quick calculations on
the numbers you supplied.  The self resonant frequency of the secondary is
abound 2.9 mhz, including 2 pf for the toroid.  The primary should be about
2.85 uh.  This should tune with a .001 uf cap.  You might try tuning it by
using a .001 uf cap and adjusting the size of the toroid (or top load) to
change the frequency.  This coil is so small and the resonant frequency so
high, it is going to be quite touchy.  Your body will probably affect the
tune from a couple of feet away.  Also, your primary may be shorting.  I
think the standard insulation on #12 house wiring is only rated at maybe 600
to 1200 volts.

Ed Sonderman