Re: Primary/NST case coupling effects

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

Original poster: Esondrmn-at-aol-dot-com 

In a message dated 11/20/03 7:30:49 PM Pacific Standard Time, 
tesla-at-pupman-dot-com writes:


> > I haven't noticed any problems locating a normal metal cased
> > nst, with case
> > grounded, below the primary when the spacing is about 12" or
> > greater.  I
> > haven't tried it closer but we know any large metal objects
> > will load the
> > primary and rob power from the system if located within the
> > field produced
> > by the primary.  I would expect it to lower the self resonant
> > frequency of
> > the primary as you reduce the distance between the primary
> > inductor and the
> > transformer case.  It should induce RF currents into the
> > case, which is
> > grounded.  I doubt it would couple through the case and into the
> > windings.  I don't think it reduces coupling since that is
> > determined by
> > the physical relationship between the primary and secondary.
> > Since it robs
> > power from the primary system, you could probably then
> > increase the primary
> > / secondary coupling without causing racing sparks because
> > the amount of
> > power being coupled to the secondary is less.
> >
> > Just my thoughts, Ed Sonderman
>
>
>
>
>Thanks Ed.
>My NST is less than 6" below the inside of my conical primary, I will move
>it and see if it makes an appreciable difference.
>This is going to be a pain as the primary winding is part of the lid that
>encloses the NST in a wooden box.
>See: http://www.users.bigpond-dot-net.au/broken.trout/DSCF0015.jpg


Nice looking coil project.  Because you are using a conical primary, I 
doubt you are loosing much power by having the nst below the primary.  Try 
taking it out of the box and using a tempory lash up to test it.  Let us 
know if performance is changed.  Boy, it sure looks like your coil would be 
overcoupled.  Do you get racing sparks?  How much power are you running and 
what size cap?

Ed Sonderman