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Re: Sword-like VTTC spark pix at my website

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <cwillis-at-guilford.edu>

Nice photos John!

I'm glad to have seen this really unusual spark in your pictures- I never
quite knew what you meant before.  My coil does not exhibit this
phenomenon, but I use a horizontal breakout and a larger topload.   With
smaller CW coils, I can get a single vertical strand of arc into air (the
811-a coil schematic at www.angelfire-dot-com/electronic/cwillis/811acoil.html
will do this) but the appearance is not the same.  I think that by using
vertical breakout, heated / ionized air rising through the electric field
can strongly contribute to discharge shape and length, maybe forming a
bubble or column of warm, rather conducting gas over the topload for the
next spark to "aim into."    I'll have to make some adjustments and see if
I can reproduce the effect on the staccato 833-A coil.

One interesting effect I do see on the 833-A coil are sparks that have
"knots" or beads in them, in some cases the beads seem to be actual
looping-back of the discharge around a 0.25" radius or so.

On the subject of tube coils, I feel the irrepressible urge to build
another 'un soon- for some reason, classwork just doesn't provide many
thrills in life. So I'm planning to go with a push-pull oscillator, with
4CX300's or similar (if I can afford them) or some "no-name" tubes from a
diathermy machine I recently sacked.  My goal is to make a "half-wave"
coil, with two secondaries base-fed off coils tightly coupled to the tank
inductor.  MMC capacitor.   I'd like to include a "super staccato" cathode
grounder and the good old level-shifted supply.  If you (or any of the
other tube coilers) have tried "half-wave" tube coils I'd be interested to
know.  Also, if you have advice regarding using the ceramic tubes I could
use it- I have always stuck with glass before.

Thanks for posting those pictures- they have certainly made a worthy
conversation piece!  

-Carl Willis