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Re: Hi Q Quest (was sync TC latest results)
From: FutureT-at-aol-dot-com [SMTP:FutureT-at-aol-dot-com]
Sent: Tuesday, November 11, 1997 10:45 AM
To: tesla-at-pupman-dot-com
Subject: Re: Hi Q Quest (was sync TC latest results)
> I replaced the 4 1/4" x 23", #28 formvar secondary with a 17" x
> 17" #24 pvc insulated wire secondary also on a polyethylene form.
> The new secondary has 470 turns, L = 67mH, F = 110kHz with
> toroid. The old one had 1500 turns, L = 44mH, F = 135kHz with
> toroid. Based on wire resistance and reactance the new coil
> should have a much higher Q, but I didn't measure it. Perhaps
> the pvc insulation hurts the Q? Coupling is k = .1 for either
> secondary.
All,
I'm updating my own post here: I measured the Q of the new
coil using a 600 ohm signal generator, the results may not be
precise because of the generator impedance, but the results
should give some idea of the relative Q's. The Q of the new
coil = 192. Q of the old coil = 100. Yet, the old coil with the
thin #28 wire gives 46" sparks at 700 watts. The new higher
Q coil requires 800 watts to give the same spark length. I can
only conclude that the physical size of the new secondary is
so large, and has so much isotropic capacity, that it is too much
for the input power to handle. For a proper comparison of Q's, a
secondary of the same size but higher Q would have to be built,
but that is difficult to do. BTW, I had posted the incorrect freq.
for and L value for my 4 1/4" by 23" secondary, but I corrected it
above; (44mH, 135kHz).
The large secondary required that the toroid be raised 8" above
the secondary to give best results. The small narrow secondary
seemed less affected by toroid height. I can only conclude that
when the toroid greatly overhangs the secondary, it's height
becomes less critical. I've also seen this effect in tests of other
coils.
Using the small toroid, the spark was about the same length
using the high Q secondary, as with the low Q secondary, but
the sparks may have been brighter with the high Q secondary.
These tests suggest that for best results, most of the isotropic
capacity should be contained in the toroid, with only a small
amount in the secondary. But it is possible that I'm seeing the
effect of some other unknown variable...there are so many
variables in TC work that wrong conclusions are easily reached
when unknown variables are not controlled for. That is why it is
so important that people try to verify other's findings.
Comments welcomed,
John Freau