Re: Tap tunable secondary

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

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

In a message dated 12/29/2001 6:48:16 AM Pacific Standard Time,
tesla-at-pupman-dot-com writes:


>
> Subj:Re: Tap tunable secondary 
> Date:12/29/2001 6:48:16 AM Pacific Standard Time
> From:<mailto:tesla-at-pupman-dot-com>tesla-at-pupman-dot-com
> To:<mailto:tesla-at-pupman-dot-com>tesla-at-pupman-dot-com
> Sent from the Internet 
>
>
>
> Original poster: "Area31 Research Facility by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <rwstephens-at-hurontario-dot-net>
>
> Terry,
>
> Why not wind a smaller coil on a short form that can be rotated within the
> bottom end of the secondary resonator.  A classic goniometer. If you are able
> to wind this coil on a plastic sphere rather than a cylinder, so much the
> better.  Probably an application for the 'strips of double sided tape' school
> of keeping wire in place while winding.
>
> Wired electrically in series with the bottom of the secondary coil and your
> source oscillator through the magic of flexible flying leads, and rotated by
> an
> insulated shaft it can be set easily during operation by hand to boost or
> buck
> a portion of the secondary Z,  thus fine tuning it to match the frequency of
> your CW power supply.  
>
> You didn't say if your secondary was a stand alone series fed resonator or
> one
> immersed in the magnetically coupled field of a helical primary.  If the
> latter
> this goniometer technique will also affect coupling, so in that case you
> might
> want to foreshorten your secondary resonator and use an outboard goniometer
> (full outer and rotating inner coil set) series connected with the bottom
> connection of your HV resonator secondary, and away from the magnetic field
> of
> the primary coil.
>
> Taps work well on beer kegs.  Can you get Corona on tap?
>
> Regards,
> Rob
> >
> > ----- Original Message ----- 
> > From: <mailto:tesla-at-pupman-dot-com>Tesla list 
> > To: <mailto:tesla-at-pupman-dot-com>tesla-at-pupman-dot-com 
> > Sent: Saturday, December 29, 2001 00:07 
> > Subject: Tap tunable secondary
> >
> > Original poster: "Terry Fritz"
> <<mailto:twftesla-at-qwest-dot-net>twftesla-at-qwest-dot-net>
> >
> > Hi All,
> >
> > I am having problems tuning my CW coil.  It is run off a variable frequency
>
> > 900 watt, 325 to 375 kHz, industrial plasma power supply.  I can wind 
> > matching transformers on big 3C8 cores to fix input impedances, but the 
> > frequency is a problem.  It has a master oscillator frequency control so it
>
> > does not track with fancy feedback, PLLs or anything like that.  But I can 
> > adjust the frequency by hand.
> >
> > The problem is the secondary frequency.  If I place different top loads on 
> > it (like the power arc tonight) It tends to drop the optimal resonant 
> > frequency too low and I can't get to the optimal frequency given the power 
> > supply's range.
> >
> > So I was thinking of making a new secondary with tap points on it so it 
> > could be taped at different frequencies.  About 5 inches on one end will 
> > have a bunch of wire loops coming out.  I don't know if it would be best to
>
> > put these taps at the top or bottom of the coil.  I am worried about 
> > autotransformer action and other problems with the unused windings.  
> >
> > Any thoughts on this are welcome.  I don't remember anything like this 
> > being discussed before but maybe the long time tube coilers have run into 
> > this and have some ideas.  I want to pump the full 900 watts forward (plus 
> > 250 reflected if needed) into a power arc to see if I can make the sparks 
> > Richie got.
> >
> > Cheers,
> >
> > Terry
> >
> >
> >
>



I've thought that perhaps a way to do this is to have the primary, or a portion
of it, made from flexible cable.  Wind the primary, or at least the
flexible-cable part of it, in a flat spiral and directly under the secondary. 
Then arrange to have a push-pull non-conducting rod attached centrally to the
flexible part of the primary and extending horizontally outward away from the
assembly.  Push/pull the rod in & out to cause that flexible part either to be
uniformly coaxial with the rest of the primary or to be pushed inward along a
diameter.  In the latter instance, the inductance of the primary will become
diminished because of partial cancellation of flux, thus effecting tuning of
the primary tank.

Ken Herrick