Re: strange vttc

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

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


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???
>
>How many turns did you end up with? Inductance does vary with the
>square of the number of turns to a crude approximation (for less than
>ideally lumped coils). The tolerance of the cap may also have played
>a prominent part in the result.

Hi Malcolm,

I ended up with 23 turns as i remember, when using the 3nf cap.  Used 24 
turns with the 2nf cap.  Seems like there should have been a larger change.
I think that the Q of the tank circuit changed a LOT from 2nf to 3nf.  The 
3nf also had a very broad tuning range that worked fine, but 23 turns 
seemed about the best for plate redness and spark length.



>   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.
>
>And probably also the degree of coupling between primary and
>secondary.

Definately!

Steve


>Malcolm