Re: Using sync gaps

I understand what you were referring to now. When I hear the term
matching, I auto-think (xfmr match - just a habit I guess). Yes I agree
with your explanation. An example is my coil. It was the geometry that
kept me down to .06uF as a safe place to start and I could always increase
from there. Thus, I was matching the cap and power input to the geometry
and construction of the coil including the RSG.
Thanks again for the explanation,

Tesla List wrote:

> Original Poster: FutureT-at-aol-dot-com
> In a message dated 98-09-29 01:49:44 EDT, you write:
> <<
> > John, one question,
> > My coil (12.5" x 34.2"), 18awg, etc.. is now using a cap
> > size of .06uF = 12.4J. The resonant size cap for this
> > coil based on xfrmr impedance of ~20k ohms was 0.128uF.
> > This created a bang size of ~25J! Taking the good advice
> > of experienced coilers on this list, I halved my cap
> > size to prevent "smoke, etc..". Wouldn't you say .06uF
> > is a large enough capacitance to provide plenty of
> > pudding to the streamers at 120bps? This cap isn't
> > matched to the input impedance but are all bets still
> > off?
> > Bart >>
> Bart,
> When I said matched, I didn't mean matched for
> resonant charging, I just meant matched to maintain a certain
> power input.  What I was really refering to is the situation where
> someone has a certain sized cap, it could be .06uF, and they're
> running at let's say 300 - 400 BPS, then they keep the same cap,
> and install a 120 BPS sync-gap, and are surprised to obtain less
> spark output.  They should go to a larger cap of around .12 or a
> little more to keep the input power more or less the same as it was.
> But if they aren't using very many primary turns to start with, then
> when they go to the larger cap, the higher primary currents that
> result from the combo of the larger cap, and the fewer turns needed
> to tune, may hurt the primary Q, due to gap losses, especially
> using narrow secondaries having low inductance.  In a case
> like this, best results from
> the sync gap may require a complete TC re-design, including more
> inductance in the secondary, to allow more inductance in the primary,
> to give a higher tank surge impedance, etc.  The overall design
> should be built in a matched or synergistic way in this sense.
> If you were running at let's 200 BPS (calculated) originally, you
> may get (about) the same spark length using the sync gap, even
> keeping the .06uF cap, because a 200 BPS system run on 60Hz
> AC will actually fire somewhat fewer than 200 times per second
> since the gap won't fire when the electrodes present too low on
> the AC sine wave.  But if you're running at 300 - 400 BPS or so,
> then I would think that you'd need a larger cap than .06uF to maintain
> the same spark length when you go to the 120 BPS sync gap.  In
> any case, a lot of coils use a .128uF cap without anything smoking,
> but the components do need to be beefy enough to handle the currents.
> I have not tested any sync gaps above 2kW input however, I
> unfortunately don't have the room   :(
> John Freau