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Re: Questions on Coil performance

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 5/7/02 12:02:37 PM Eastern Daylight Time, tesla-at-pupman-dot-com

Hi Andy,

If you're using the untriggered static pipe gap, and you left the spark 
gap spacing unchanged, then the only way the spark length can increase
is via a faster break rate.  It may be running at a higher break rate,
but this might not help too much perhaps.  You may have to adjust
the gaps for a wider spacing, of course this stresses the NST.

If you're using the triggered gap, maybe it's running too hot
with the larger NST, and not firing or quenching correctly.
It's also possible the controller doesn't have enough phase range,
with the particular NST/cap value combo.  If this is the case,
then the controller knob will be at one end of the useable range.
The system may be running in the R mode rather than the N 
mode perhaps, rather than vice versa.  

Toroid height is not too important in some cases.  A higher
toroid usually gives longer output sparks (a couple inches),
but can result in
corona coming off the top winding of the secondary.  If the
toroid is too small, this can limit the spark length.  For
best results with a 15/60 NST, the toroid should be about
6" x 26" or so for a corrugated dryer duct toroid.  Still, a 
4" x 17" toroid should be able to give a 48" spark.  Probably
an 0.02uF cap value is best for a 15/60 (LTR), using a static
gap.  Using a triggered gap, a larger cap value may be better,
perhaps 0.028uF or so.   You may need to add another cap
string to raise the cap value higher, while maintaining an
adequate voltage rating.


> Hello all,
> I have a couple of questions.  When I ran my coil with a 15/30, I got 30"
> arcs with 15 geek caps in series.  When I moved up to a 15/60, I can only
> get 33" arcs with 12 caps.  When I went to 11 caps, moving closer to LTR,
> the arcs were even shorter.  It was in tune each time as I use a roller
> inductor to tune it.  Also, how important is toroid height?  I see the same
> performance whether it is 1" or 6" above the secondary.  What should it be?
> Any help would be much appreciated.
> Andy, KB3EWY