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Re: More Coupling...
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
A small change in primary height seems to give quite a large change in
k as the primary starts to fall below the secondary.
Bart, I'd like to know the height of your primary wrt the secondary
base (p-s) at which your measurement was made.
Ed Phillips <evp-at-pacbell-dot-net> wrote:
> Grover (and BS C74) have occupied honored places on my book shelf
> for many years! I'll look up Grover's tables at work tomorrow.
> I never really studied that part; just copied his formulae and
> tables for solenoids.
I only recently came across Grover's work, thanks to Mark Rzeszotarski
who drew my attention to it when I was struggling to map out the
mutual inductance of the secondary. They've been really useful and
(net of software errors!) quite accurate too.