Re: VTTC/SSTC Spark Appearance Comparison

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Steven Ward by way of Terry Fritz <teslalist-at-qwest-dot-net>" <srward16-at-hotmail-dot-com>

Hi,

John really does have a much better understanding about spark forming than 
i do, but let me describe what i have gone through.  It seems to me, that 
at low powers, sword sparks are easily achieved.  At high powers, the 
effect can be very hard to achieve.  I once built the dual 833A coil with a 
6"x24" secondary and a 25 turn saucer primary with 6nf tank capacitance 
(thats pretty big!).  This setup was pretty touchy and disappointing in 
that it was really hard to tune and get proper feedback.  I did manage 22" 
sparks, but they were wild and forked, and very loud!  They were not 
impressive in that the coil was mamoth!  But even in the smaller dual 833A 
setup, they started out branched and sloppy (the sparks that is). Only 
after a few months of work and fine tuning did they really get straight 
like they are now.

Dan, The staccato controller has very little to do with the straightness.
Oddly i noted something:  at high bps (30) the sparks would hit the 24" 
target say 1 out of every 5 pulses (not too great), but then at like 2 bps, 
i got a 24" hit EVERY TIME!  Most of those photos are at low (under 10) 
bps.  The higher BPS ones simply have more sparks present, and you will 
note that in those photos, not so many sparks hit 24".  But really the 
point is negligable though it kinda supports what you said.

I really think that the sword spark depends on too many things to pinpoint.
In my coil, several things effected it.  PSU voltage doubler capacitance, 
tuning, grid feedback coils and grid leak resistance.  Also the toroid 
really does help!  But even these few variables take a long time to get right.

Steve Ward.






>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Re: VTTC/SSTC Spark Appearance Comparison
>Date: Tue, 01 Apr 2003 12:23:22 -0700
>
>Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
><FutureT-at-aol-dot-com>
>
>In a message dated 4/1/03 10:31:04 AM Eastern Standard Time, 
>tesla-at-pupman-dot-com writes:
>
>
>>So my question is, why are VTTC arcs perfectly straight, and SSTC
>>arcs not? Don't they work the same way? They both (VTTC and SSTC)
>>switch CW power into the primary right? I know exactly how SSTC's
>>work, but I've never looked into VTTC's, so can someone please inform
>>me exactly...exactly...what the primary sees in a toob coil? If you
>>can describe, or link to a waveform, it'd be great.
>
>
>Justin,
>
>Not all VTTC's produce straight sparks.  Many of them produce the
>same sort of branched sparks as SSTC's produce.  There are many
>factors that affect the spark appearance.  Some of the factors are;
>tuning, power supply, component spacing, feedback adjustments,
>RF envelope shape, pulse rate, secondary design (maybe), etc.
>
>For example, my 24" spark dual 833A coil gave branched sparks
>until I replaced the plate transformer with an MOT.  Then the sparks
>became very swordlike.  When I re-configured the coil into a portable
>design, the sparks became branched again.  The same thing happened
>on my 15" spark staccato TC.  My 36" spark TC always gave branched
>sparks no matter what I did.
>
>I did a series of tests in which I varied the RF envelope.  Envelopes
>which rose gradually gave straighter, longer sparks than envelopes
>which began at a high level, and stayed steady or declined.
>
>the primary waveform in a VTTC is an RF sine wave forming an
>envelope which rises and falls with the 60Hz input power.
>
>My VTTC's can be seen at my website at:
>
>
><http://hometown.aol-dot-com/futuret/page3.html>http://hometown.aol-dot-com/futuret/page3.html
>
>click on the links as needed.
>
>John
>