Re: Resonance, and now magnifiers

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

Original poster: Bert Pool <bert.tx-at-prodigy-dot-net> 

At 09:04 PM 7/19/2004 -0600, you wrote:
>Original poster: Paul Nicholson <paul-at-abelian.demon.co.uk>
> >From another thread:
> > Using a large top load capacitance ... helps force the
> > best resonant point near the 1/4 lamda point.
>
>[snip - though I hate to, because Paul Nicholson wrote some very good 
>points so well!]


>This 'middle' capacitance affects the 3/4 wave mode more than
>the 1/4 wave mode, so we now have the means of tuning each mode
>with some independence of the other.  This tends to be done by
>splitting the coil at the appropriate point and maintaining the
>connection with a piece of wire (the 'transmission line' of
>magnifier terminology).  The resonator now finds extra
>capacitive loading near its 3/4 wave voltage maxima: the top
>end-effect C of the secondary, plus the transmission line C,
>plus the lower end-effect C of the tertiary.
>
>If done correctly, the 3/4 wave mode is now timed to reach
>a voltage peak simultaneously with the fundamental after a
>certain (design choice) number of RF cycles have elapsed.

On my large magnifier, I use a 12 inch wide, fifteen foot long strip of 
aluminum flashing as a transmission line.  The surface area is quite large, 
because both exposed sides provide capacitance, as opposed to a cylinder 
which has an inside surface area that is wasted. The magnifier system loves 
the capacitance, and Paul's explanation does a very good job of explaining 
why.  The transmission line, if designed as a large capacitance, acts as an 
additional energy storage device, as well as bringing that 3/4 mode 
resonance more into "tune" with the extra coil/topload.

Tesla ,himself, said adding capacitance to the top of the secondary of a 
magnifier would improve operation (Colorado Springs Notes, September 19 
1899 page.)


>Why bother going to all this trouble?  Well the 3/4 wave
>mode is excited anyway, to some extent, whether we like it
>or not.  So rather than waste that energy, we might as well
>try to use it.   The extent to which higher modes are excited
>in any coil depends on how the primary induction is distributed
>along the coil.  If we want to achieve high coupling (for what-
>ever reason) we cannot do so by spreading the primary along
>the secondary, for reasons of voltage breakdown.  So we have
>to apply strong coupling to just a short region of the
>secondary at its cold end.  It's this highly end-concentrated
>coupling which tends to put a greater proportion of the bang
>energy into the higher resonances of the secondary.  Therefore
>it's a natural evolution of the TC to try to tame and exploit
>these.[*]

[snip again]

Paul's extensive message is certainly one I am archiving - it's packed full 
of good insights.

Bert Pool