Re: strange vttc

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

Original poster: "Steven Ward" <srward16-at-hotmail-dot-com> 

I think VTTCs have this magic instability in their operation that makes the 
idea of fine tuning go out the window for a moment.  I once substituted a 
3nf tank cap in for my 2nf cap, and i figured i would tune at several fewer 
turns.  Well, when all was said and done, i ended up only 1 turn less than 
before! even though my tank cap was 50% larger!  Whats the deal with 
that???  I think also that the Q of the tank will play a large roll in how 
things work out and how close you must get the tuning.  Some of my VTTCs 
will tune to a very wide variety of tap points, others will not.  I think 
part of it has to do with the feedback and its RC circuit getting in with 
the mix of things.  At the moment i havent thought about it enough to 
really give any good answers, just some thoughts i had...

Steve


>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Re: strange vttc
>Date: Mon, 29 Mar 2004 22:23:15 -0700
>
>Original poster: "Jim Mitchell" <electrontube-at-sbcglobal-dot-net>
>
>I don't think this is all that strange.  For one,  with a VTTC,  it is not a
>self resonant system.  So the VTTC will be running at the frequency of the
>tank LC circuit,  which may not be the EXACT resonance of the secondary.
>Therefore, you reading a different frequency output on your scope is
>probably due to the coil not being in exact resonance.  Just like on an
>oscillator driven SSTC, you have to retune sometimes when the output grows
>because of it's capacitance.
>
>Regards - Jim Mitchell
>
>----- Original Message -----
>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: <tesla-at-pupman-dot-com>
>Sent: Monday, March 29, 2004 6:42 PM
>Subject: Re: strange vttc
>
>
> > Original poster: Mike Poulton <mpoulton-at-mtptech-dot-com>
> >
> > Tesla list Wrote:
> >  > Original poster: "claude masetto" <claudmas-at-optusnet-dot-com.au>
> >
> >  > Hello all,
> >  > I have been playing around with my vttc and have been taking some
> >  > observations with my scope and have noticed something strange. The res
> >  > frequency of the resonator as calculated by Java TC is 342khz. When I
> >  > measured it with a signal generator and a scope the result was 360khz.
>Close
> >  > enough for me.
> >  > I then setup an antenna with a scope probe attached to it and measured
>the
> >  > resonator frequency with the the coil running and noticed it was
>255khz. The
> >  > coil is in tune, as best as I can get it because it performs great.
>Twin
> >  > 304tl tubes with 30" spark on a good day.
> >  > I can't understand the difference in the two measurements. I have
>checked
> >  > the results over and over.
> >
> > Is that the frequency when producing a 30" discharge? Does it increase
> > when you turn the power down until the discharge disappears? If so,
> > then the additional capacitance of the discharge is pulling the
> > frequency down (as expected). That is a very large change, though --
> > much more than I would have anticipated. Do you have a topload of any
> > kind on the secondary?
> > -------------------------------------------------
> > Mike Poulton
> > MTP Technologies
> > mpoulton-at-mtptech-dot-com
> > KC0LLX (70cm AM ATV, 33cm/12cm FM ATV, Omaha, NE)
> >
> >