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Re: Not enough pimary inductance?



Tesla List wrote:
> 
> Original Poster: Jim Lux <jimlux-at-jpl.nasa.gov>
> 
> Tesla List wrote:
> >
> > Original Poster: "chris morgan" <crmorgan-at-hotmail-dot-com>
> >
> > Not enough pimary inductance?  You don't necarcarly have to go and build
> > a whole new coil, why don't you just put a couple of loops in the
> > circuit somplace to add inductance and lower the freq?  Sounds like a
> > good idea to me.
> 
> You can add inductance anywhere, but you might as well make it with your
> primary, so that the field from that inductance can couple to the
> secondary.
> --
> Jim Lux                               Jet Propulsion Laboratory
> ofc: 818/354-2075     114-B16         Mail Stop 161-213
> lab: 818/354-2954     161-110         4800 Oak Grove Drive
> fax: 818/393-6875                     Pasadena CA 91109

	I have a small coil here which has a "roller coil" in series with the
primary for tuning.  I don't have the numbers handy at the moment, but
it has a total inductance range of from close to zero to about 1/3 of
the primary inductance.  I can tune the primary using this arrangement
(coil is tuned through long strings wrapped around a pulley) and find I
don't seem to lose much in the way of streamer length by this method as
contrasted to having all of the primary inductance at the base of the
coil.  That is obviously better, but for a quick start I'd wind any old
tapped coil, play with it until I got the tuning right, and then build a
new primary of the appropriate inductance, plus a few turns for safety.

	The primary tuning has a large effect when the input voltage to the
transformer is so low that the spark rate is only a few a second, but at
full input and spark rate it has almost no effect at all.  I believe
this is because the loaded Q of the secondary is quite low under this
condition.  

Ed