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High volt. vs. low, also 60 bps re-visited
Dave, Barry, Malcolm, Finn, Reinhard, Richie, all,
I did a couple of new tests:
Test 1. I compared high voltage, small cap operation with lower
voltage, larger cap operation (120 bps) Predicted lengths
are based upon the square law:
Watts C(uF) scope div. toroid actual length
750 0.0147 5.3 6x26" 47"
750 0.031 4.9 6x26" 47"
(the voltage on the cap in the second test was adjusted to keep
the input power constant. It's clear from the results that if there's
any advantage to be gained from a higher voltage, it's very slight,
i.e. too small for me to measure. Reinhard will be pleased !!
My original tests which showed an advantage at higher voltages
was flawed due to the use of two different NST's. I'm measuring
things in a more precise way these days.) The % difference in
voltages used, is equivalent to an increase from 15kV to about
20kV.
Of course in the recent past, I compared the TC operation while
producing 42" sparks using the .0077uF cap at about 600 watts,
and the .0147uF cap at the same wattage but lower voltage to
give the same bang size. Again, the higher voltage did not seem
to help. Any theoretical advantage must be too slight for me to
measure.
Test 2. I removed some spinning electrodes from the sync gap to
give 60 bps, and doubled the cap size from .0147uF to .031uF to
keep the power input ~the same. The results were very poor. I had
problems with resonant buzzing and flashovers at the gap, and the
sparks were weak and thin. This was with the 6x26" toroid, I didn't
try any others. I tried firing on the negative, then the positive ac
peaks of the input ac, but this didn't make any difference, and I
didn't expect any difference. In the past (1 year ago?), I tried 60bps,
with the .0147uF cap, and a smaller toroid, and the results were
excellent. Nevertheless, I'll probably abandon these 60 bps tests
for now. These results seem to hint that high break rates may work
better at higher powers, hmmmm.
John Freau