S.s. info...re: differing secondaries

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Original poster: "Kennan C Herrick by way of Terry Fritz <twftesla-at-uswest-dot-net>" <kcha1-at-juno-dot-com>

S.s. coilers may be interested in the following:
 
As I've previously reported, my s.s. system utilizes an untuned primary and
also a means for making the excitation frequency always exactly that of the
secondary's resonant frequency.  I have now made two secondaries, both
according to "HERRICK'S RECIPE..." posted in 8/00, one 52" high and the second,
36" high.  Fr's are ~100 KHz and ~125 KHz respectively.  I use the Landgren 6"
x 24" toroid with no added breakout-point.
 
I find that, while the 52" coil yields very satisfactory sparks, those from the
36" coil are markedly less so.  It might be that the driving impedance for the
spark is diminished, away from optimum, by going to the lower turns-ratio
(~2:760 vs. ~2:1100).  But then, the operating frequency increases with the
shorter coil, so one might expect the driving impedance to be higher due to
that.
 
Manually sweeping the two coils with a signal generator shows that their Qs are
essentially the same--around 100.  So with a Q of 100 and with only 760 turns
in the secondary, I am finding that spark breakout still occurs from the 6" x
24" toroid.
 
I also notice the following:  1.  The electric field, as measured by a
partially-shielded scope probe placed ~4' away from the coil c.l., is
essentially the same with both coils--both at the peak of the envelope when the
spark breaks out (as expected since it's the same toroid) and also during the
remaining ~5 ms spark duration.  And 2:  The input line (mains) current,
directly equal to average primary current in my case, is essentially the same. 
It should be noted that, during the entire pulse-burst time, the secondary is
driven at its instantaneous self-resonant frequency.
 
So I tentatively reach this conclusion:  The factor that mostly caused the
decrease in spark energy was the increased operating frequency since a) Qs were
the same, b) primary power was the same and c) the turns ratios in the two
cases were sufficiently high to allow spark break-out from the same toroid. 
Thus I would conclude that one wants to employ a secondary construction
technique that minimizes Fr while at the same time providing a Q vs.
turns-ratio condition such that spark break-out reliably occurs from the toroid
of choice.
 
My next task will therefore be to construct another 36"-high secondary, also
with 20 ga. wire but close-wound instead of spaced ~.05" center-center.  That
will bring the frequency down substantially while maintaining ~1100 turns,
although Q will diminish due to the lack of spacing.  But the lower Q will be
compensated for by the higher turns-ratio, in bringing the toroid voltage to
break-out potential.  So, we'll see...
 
Comments, anyone?  Am I missing something?
 
Ken Herrick