Re: Primary Resonance

	I think the effect you are observing is due to the 
varying leakage inductance of the secondary.  I have noticed
that, when I use a secondary (for the neon) capacitance anywhere
near "resonance" that I get a two-valued effect as I increase
primary voltage with a variac.  I think that what happens is 
that at low flux density in the core the leakage inductance
is high enough to resonate, causing the voltage (and hence
the current) to increase abruptly, at which time the inductance
drops.  At least, that theory explains what I have observed
here in the past.
	Another thing to note.  Before the spark occurs, the
Q of the neon secondary and the TC primary resonant circuit
is high enough that it may take several cycles of the 60
cycle power for the voltage to reach maximum.  If you use
a large capacitor and bring the primary voltage up slowly
you can certainly get to a point where the spark gap is
firing, but only a few times a second (once every several
cycles of the power frequency).  See the same effect in
a circuit simulation I have running in Electronics Work Bench.
Ed Phillips