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Re: sparks
In a message dated 99-02-08 06:05:50 EST, you write:
<< My question is this: I've read many previous posts about people getting
> 50"-60" sparks and more from a 6" secondary. The most I've been able to
> obtain is about 36"-40" my specs are below:
> 15K/60 ma NST
> 16 turns of 1/4" copper primary spaced 3/8"
> 6.5" X 28" secondary wrapped with 20awg
> 4" X 20" toroid
> 3 rolled poly caps in series = .01 uF
> RQ design circular static gap -6"pvc/1-1/4"copper tubes with muffin fan
> Did I blow it using 20awg? Is there something I can do to improve spark
> length? Or is this the best I can expect from 60ma? Any suggestions from
> the more skilled coilers out there is appreciated.
> Bob V
>>
Bob,
The biggest contributor to spark length is input power. The size of
the secondary has a much more modest effect. However the inductance
ratio between the primary and secondary does seem to be relatively
important. The spark length you are obtaining is about normal for that
size NST. If you are getting multiple streamers from your toroid, that
will reduce their length somewhat. But folks often prefer multiple
streamers...it looks more exciting. (A larger toroid will produce
fewer streamers). If you widen the spark gap spacing
you might get longer sparks, but you'll probably destroy the NST. It's
best to keep the spark gap spacing reasonable and accept the present
performance.
If you add another identical NST in parallel, and double your capacitor
size, and use a larger toroid, you should get about 40% longer sparks,
if your gap can still quench OK, at the higher power level.
I use a low break rate (120bps) with a synchronous rotary gap, and
a larger (6" by 26") toroid, to obtain 64" sparks using a 15kV, 60ma
NST. The secondary is 4 1/4" by 24", wound with #28 wire. This
secondary is running on the edge of breakdown however. The
cap is .014uF. In an earlier experiment, I used a static gap and
obtained only 48". The main reason for using a large secondary
on a powerful TC, is to prevent voltage breakdown, and to reduce
toroid to primary strikes.
John Freau