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Re: Tesla and Measurements.
[snip a LARGE section on primary/secondary impedance matching and L/C
measurements and hypothesis]
> The upshot is that a match is effected only for one set of
>secondary spark conditions. I have scoped this using a discharge rod
>set at different distances from the secondary terminal and seen it
>happening (the differences in VSWR etc.).
> What I am postulating here is that for a given power throughput
>(read secondary spark) and a particular secondary coil, there is an
>ideal primary configuration that effects a perfect match to give an
>arc of a certain length.
Malcom,
My experiences with coils supports exactly what your scope testing shows,
i.e., there is an ideal capacitor/primary setup for each secondary and
supply transformer setup. I have a medium size coil I call the Green Hornet
(wound with 15 gauge bright green enamel wire) that I have done a great deal
of work on trying different capacitor/primary turns ratios. I greatly
reaspect both Richard Hull and Richard Quick's belief that you can use a
small cap and large primary coil inductance over the old big cap/small
primary idea; I just don't find that paradigm works well with this coil.
Back when I started working with this coil, I had built six of the Hull-type
caps so I had a lot of capacitance available with which to experiment. I
was using six 9 kv 60 mil neon transformers as a power source. Never was I
able to use a many turn/ small cap arrangement and achieve "optimum" output.
My absolute best performance was with between .03 and .04 ufd with three
primary turns. If I tried less capacitance and more turns, output dropped.
If I tried more capacitance and fewer turns, output dropped. The Green
Hornet _liked_ 0.03 to 0.04 ufd and three turns, so I stayed with what
worked. I was using a rotary gap (plexi disk driven by a skill saw motor -
_loud_) and performance DROPPED when I tried adding a static gap! So I
ended up using just the rotary by itself. Today my rotary and series gap is
much improved, and I have since gone to a pole pig and given away my neon
transformers. I'm now using a bank of Sprague door-knob caps immersed in
oil, and recently I fired up the Hornet. Even with different caps and a
much bigger transformer, the Hornet still ended up wanting 0.03 ufd and
three primary turns. I also found that there was an optimum top capacitance.
I tried a total of three different toroid tops, and retuned to each, and
again, there was one top which gave an optimum output over the other two,
even when trying different mixtures of capacitor/primary driving. I am
happy to report though, that this coil does now enjoy the extra series
static gaps. That must be because it needed the extra quenching because of
the larger supply transformer.
Anyone else out there have a coil that likes a specific capacitance/primary
setup?
Bert