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RE: 3-1000z VTTC - Record breaking final run

Original poster: "Ross Overstreet by way of Terry Fritz <twftesla-at-uswest-dot-net>" <ross-o-at-mindspring-dot-com>

The addition of the toroid changed F(r) from 328 khz to 250 khz.  It has a
3" tube and a 14" total OD.  I added several taps to the primary so I could
instrument tune the primary tank to the loaded (250) or unloaded (328) freq
of the secondary.  I also provided a means of disconnecting some of my
primary C and added taps to the primary L so that I could maintain the
instrument tune.  Furthermore, I can swing the resonant freq of the primary
tank about 50khz with the 40pF vacuum variable that I am using.  Given all
of this, I still have a hard time finding a maxima as far as tuning goes.

The next tube circuit will not use the toroid.  I prefer a larger ball of
arcs to the more vertical arcs and slightly thinner arcs that I saw with the

(Q #1)
Can anyone tell me more about matching the Z of the primary tank to the Z of
the tube?  Is this just another myth or is there some important theory here?
I tried both options (Low C, high L / high C, Low L)while keeping F(r) about
the same and didn't see any significant difference.

(Q #2)
What is the origin of the VTTC oscillator that is commonly used?  Brent's
book demonstrates that it uses ideas from both the Hartley and Armstrong
Oscillator but I'm missing the big picture.  I also haven't seen it in any
other literature.  Is the optimal circuit to be using for the task at hand?

I note that Dave Sharpe (of TCBOR fame) is a big proponent of the push-pull
Hartley configuration.  I think his reasoning is that it is most commonly
used in RF heating and other important tube based oscillator applications.
I see that it has a higher component count and higher complexity and that is
why I have avoided it.

David - watch the mov file in slow motion during the tube flash-over.
You'll see it get extremely bright.  Pyro in a bottle.

It would be a shame to give up just when I'm starting to get a grasp.  I'll
probably lash together a little 3CX2500 coil next.


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Wednesday, May 02, 2001 3:50 PM
To: tesla-at-pupman-dot-com
Subject: Re: 3-1000z VTTC - Record breaking final run

Original poster: "David Trimmell by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <davidt-at-pond-dot-net>

Ross, way to go! 28" issn't too bad, better than I have ever been able to
get. How much did you drop the Fr0 by with the addition of the toroid? Did
you tune to match with the tank C or L? Changing tank impedance may have
had more to do with it than anything else?

I have put coiling (tube, of course!) away for the time being, as I have
been focusing on my Pyrotechnics interests (not Tube Pyro!), but will
probibly get back to some old projects this summer.


David Trimmell

On Wed, 2 May 2001, Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
> In a message dated 5/2/01 12:44:51 AM Eastern Daylight Time,
> writes:
> > Hi Guys,
> >
> >  I set a new arc length record with my 3-1000z VTTC.  I managed very
> >  repeatable, multiple arc per second hits to a ground rod located 28
> >  above my breakout point.
> Ross,
> Congratulations on achieving the 28" spark length.  I use a small
> toroid on my small coil that gives 24" sparks, but I don't notice
> much difference in the arc shape.  What sized toroid are you using?
> One of the most important things for tube coils is to have a correct
> relationship between the Lp and Cp in the tank.  But all the adjustments
> are critical pretty much.
> John Freau