Re: Pri./Sec. Tuning

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>

Tesla list wrote:

> Original poster: "Mike Knowlton" <amdx@xxxxxxxxxxx>
> I have been reading this group for about six weeks now and
> see confusing info on pri./sec. tuning. ( to me anyway)
>   My understanding is you have a secondary coil with toroid (tophat) that 
> is resonant at a fundumental frequency.
>   Then you wind a Primary, and wire it with capacitors in parallel, then 
> adjust a tap on the primary until the primary is resonant at the same 
> frequency as your secondary.

Correct.

> (I understand this is performed with the secondary in place.)

No. When the two systems are coupled, two resonances appear. Tuning
with the two coils in place is best performed with transient excitation.
See http://www.coe.ufrj.br/~acmq/tesla/tuner.gif.
By the way, I would not consider other method...

>   My confusion is sometimes I see people say tune your primary lower or 
> higher. Shouldn't they ring at the same frequency?

The primary system is usually tuned to a slightly smaller frequency,
because when streamers are present at the secondary terminal, the
secondary capacitance is increased, decreasing the secondary resonance
frequency.

>   Also as a tuning method, could you lightly couple a scope probe to the 
> circuit and drive the primary with a signal generator, then watch for 
> double peaks, then adjust the primary inductance (or capacitance) until 
> you have a single peak.

You will always see two peaks, due to the "frequency splitting" phenomenon.

> P.S. I aquired an 8.5" x 42" clear plastic tube today, I think it's my 
> start to building a TC !
>  "clear plastic"? How do I find out what type of plastic this is?
> It has a 1/4" wall thickness.

Probably acrylic.

Antonio Carlos M. de Queiroz