Re: Lower secondary cself => better performance?

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-uswest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Marco,

On 8 Feb 01, at 7:53, Tesla list wrote:

> Original poster: "Marco Denicolai by way of Terry Fritz
> <twftesla-at-uswest-dot-net>" <marco.denicolai-at-tellabs-dot-com>
> 
> Hello all.
> 
> If I recall correctly, in the past it has been suggested to build a
> secondary coil with a certain H/D ratio (also) in order to minimize
> its self-capacitance.
> 
> Was therefore believed that a lower self-capacitance results in better
> performance?
> 
> How this belief has changed at the light of Paul Nicholson and the
> TSSP group results?
> 
> Regards

Speaking for myself only, what research I did in the past was aimed 
at finding the best Q with and without toploads. The recipe for 
minimizing Cself (the traditional lumped notion of Cself) for a given 
coil diameter is easy: somewhere around 0.5 - 1 H/D. You can see that 
the coefficient in Medhurst's tables bottom out at this point. 
Optimum Q is a different matter. Best Q for no topload is a 
spacewound beast with an H/D = 1. Best Q for a toploaded coil was 
around H/D = 3 for a closewind and ? for a spacewind (can't remember -
 might have been 2). Depends heavily on the size of the topload and 
its mounting height above the coil too.
     I would guess that the difference in results between John 
Freau's coil and Skip's coil for the same power input would depend to 
some extent on the relative sizes (and hence capacitances) of the 
resonators but probably more heavily on the losses in the primary.

Regards,
Malcolm

P.S. - I'm glad for you that the Thor power supply is now running to 
spec.