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

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

In a message dated 5/3/01 11:16:21 AM Eastern Daylight Time, tesla-at-pupman-dot-com 

> Given all
>  of this, I still have a hard time finding a maxima as far as tuning goes.


Thanks for the info.  I see a rather critical tune point on my tube 
coils, as far as getting longest sparks with minimum plate redness.
More below.  All the adjustments are critical.  Much time and playing
around with the adjustments is essential for best results.
>  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 
>  topload.

Interesting that your sparks were thinner with the toroid.  Mine
seem to be thicker and brighter, as well as 1" longer, but i'm using
a smaller toroid.
>  (Q #1)
>  Can anyone tell me more about matching the Z of the primary tank to the Z 
>  the tube?  Is this just another myth or is there some important theory 
>  I tried both options (Low C, high L / high C, Low L)while keeping F(r) 
>  the same and didn't see any significant difference.

Definitely not a myth.  Ed Phillips gave a formula some time ago,
for getting in the ballpark with the Z match.  If the Z match is bad,
the performance will be horrible, no doubt about it.  There's a range
that will work OK though.
>  (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?

The common VTTC circuit is a type of Armstrong oscillator.  The Hartley push
pull is a more stable, more efficient oscillator, but I like the simplicity
of the Armstrong design.  As far as I can tell, the difference in efficiency
between the two circuits is so slight, it can't be seen or measured.
I'm not sure what you mean about missing the big picture.   A VTTC is just
a power oscillator coupled to a resonator.  I don't think any other
circuit will give noticeably better results.

John Freau

>  Seeya,
>  Ross