Re: More Coupling...

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

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Paul,

Comment intersperced below.

Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<paul-at-abelian.demon.co.uk>
>
> Barton B. Anderson <tesla123-at-pacbell-dot-net> wrote:
>
> > Measured K on my flat primary for my 12.75" x 45" coil.
> > The flat primary is 16.5"ID, 0.375"wire, 0.625" spacing (c-c)
> > (or 0.375 edge to edge), and 11.6 turns in the case of using
> > my 0.06uF cap setup.
>
> > K = M / sqrt(Lp * Ls) = 627 / (107.13uH * 87.6mH) = 0.205 K
>
> Assuming this is your 1000 turn, 18awg secondary, acmi predicts
> you'll get that k-factor when the primary sits 4 cm above the
> base of the secondary winding. If the primary is level with the
> secondary base, the k is calculated to be 0.178.
>
> I've made up a graph of k against primary height relative to the
> secondary base
>
>  http://www.abelian.demon.co.uk/tmp/bart-k.gif
>
> A small change in primary height seems to give quite a large change in
> k as the primary starts to fall below the secondary.
>
> p-s
> (cm)    k
> -3     0.156
> -2     0.163
> -1     0.171
>  0     0.178
>  1     0.186
>  2     0.194
>  3     0.201
>  4     0.208
>  5     0.215
>
> Bart, I'd like to know the height of your primary wrt the secondary
> base (p-s) at which your measurement was made.
>

Paul,

My secondary was elevated 1.5" above the primary as measured from the
primary inner turn to
the first secondary turn. That's about 4cm, isn't it. Very interesting!
I've been told larger
higher powered coils get away with high coupling than say smaller coils. I
typically run at
about this setting.

I find the graph and above data interesting in that as the distance (height
of s to p) is
increased, the k value increases? I've always thought that lowering the
secondary decreases
coupling? From your data, it appears just the opposite. If this is true,
then we need to
invert our ideas about coupling and racing sparks phenomenon.

Maybe I'm reading your data backwards. Can you clarify? thanks...

Take care,
Bart