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Re: Optimum coil configuration



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In a message dated 97-03-11 12:10:10 EST, you write:

<< Hi y'all,
 	I have been operating the following setup for a while now. Because
 of business trips, winter, laziness and various personal disasters, I
 haven't gotten to do as much experimenting as I'd like.  Lately, though I
 find that I'm having a bit more time to play (and it's been warmer)
 so I got to wondering about the consistently poor (in my view) performance
 that I've gotten from my coil.
 
 	The stats are:
 	2 15-at-30 neons
 	around 50 feet of 3/8" copper, 3/8" apart for primary
 		Primary is sometimes inclined for better performance
 	a CP .025 uF capacitor
 	6.5" X 27.25" secondary
 	various toroidal terminals
 
 	The system usual tunes at about 8.25 turns or so.  The best
 performance to date has been about 22", from the largest toroid that I
 have, about 30" X 3 made from drain duct for trailers.
 	Would I get better performance given the power limitations that I
 have from a shorter secondary?
 	Would a shorter secondary cause the tuning to move to less turns
 or more?
 	
 
 Stan Harle
 Alamogordo, NM
  >>
Stan,

Your coil is a little larger than mine, and I agree, I would expect better
performance.  I did some caculations on your coil, but had to make some
assumptions to get started.  I assumed that you used #22 wire on the
secondary and that the 27.25" that you mentioned was the actual winding
length.  This would result in a H/D ratio of 4.2 with about 978 turns - which
sounds great to me, I would not change it.  The inductance should be 33.5 mh
and unloaded resonant frequency would be 249 khz.  Assuming effective
capacitance of the 30" toroid to be 21 pf, the loaded frequency would be
about 151 khz.

Assuming your primary has an inside diameter of 9.0", 50 feet of tubing
should be about 11.5 turns total.  With the toroid in place, using a .025 mfd
cap, it should tune at about 9.9 turns - unless I have missed something here.
 The total primary inductance should be about 62 micro heneries.

Your coil should perform well.  With my 6" coil, I got 34" discharges with a
12kv 60 ma transformer and a 14" toroid.  With 12 kv and 120 ma and a 30"
toroid I got 50".

I suspect a problem with your spark gap or the transformers.  If you make a
larger toroid, I would suggest going up to at least 6" diameter (torus) and
maybe even 8" or 10".  With another (good) transformer or two, you should get
well over 48" of spark.

Ed Sonderman






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