Re: Tap tunable secondary

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

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
>
>
>