Re: Bart's Coil

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

Original poster: "Paul Nicholson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <paul-at-abelian.demon.co.uk>

John Couture wrote:

> I did not use a primary capacitor so the test frequencies are
> not arbitrary...

> Eq #1      Fr = (1/6.283)sqrt(Lp/(Lm/K)^2xCc)
>   The Cc is the coil self capacity of the secondary.
> 
> Eq #2       K = sqrt(1-(Fo/Fs)^2)
> 
> Subsitute Eq #2 for K in Eq #1. 

Ah, the plot thickens.  Your equ #1 is slightly broken but I get the
gist. In this case it's the secondary that's being resonated, and
Fs, Fo, refer to tests using a s/c and o/c primary.

> In both the Fr and Fo tests the same bare secondary coil is used
> but the two frequencies are much different.

I'd expect them to be the same, providing the secondary resonance
is not disturbed by probing.  What alterations to the setup do you
make between a measure of Fr and a measure of Fo?  Surely none?

> More testing is required.

Yep.

Recommend measuring Fr (== Fo IMO) with the topload in place by
looking for a dip in the base Z - ie sig gen into base via a pad
and sweep for the biggest drop across the pad.

Then do nothing but short the primary.   Measure Fs.
Then you'll get a K factor which perhaps is most closely related to
the 'working' K factor during operation - ie the factor which 
determines how many RF cycles there are per beat - which is probably
what you really want to know.

--
Paul Nicholson
Manchester, UK.
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