Re: K formula?

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

Original poster: "Peter Lawrence by way of Terry Fritz <teslalist-at-qwest-dot-net>" <Peter.Lawrence-at-Sun.COM>

Burt,
Antonio,
          thanks for the formulas. I had found the one Antonio uses by a
google search for "coupled resonance" and a lot of weeding, and Burt's
is mathematically equivalent. I also found one "approximate" formula
(2*(Fu - Fl)/(Fu + Fl)) which does agree at these low K, and one totally
out to lunch formula, so it's good to see some agreement here.

You are correct about my primary, I have the fixed connection on the outer
most turn, and the adjustable tap somewhere in the middle. For the tuning
that these measurements were made, I think I was on turn number 9 out of
14 counting from the outside, so a lot of inner turns were unused.

(this is good for reducing K, and "racing sparks", but not good for reducing
primary-to-bottom-of-secondary sparks because of the auto-transformer effect
the outer primary turns have on the inner primary turns and their proximity
to the secondary. Everything is a trade off...).

-Pete.


 >
 >Original poster: "Bert Hickman by way of Terry Fritz <teslalist-at-qwest-dot-net>"
<bert.hickman-at-aquila-dot-net>
 >
 >Hi Peter,
 >
 >If:
 >  F1 = Upper Resonant Frequency
 >  F2 = Lower resonant Frequency
 >
 >then the coupling coefficient is:
 >
 >  k = ((F1/F2)^2-1)/((F1/F2)^2 +1)
 >
 >So, for your system:
 >
 >  k(0.0") = 0.1104
 >  k(0.5") = 0.0981
 >  k(1.0") = 0.0876
 >  k(1.5") = 0.0769
 >
 >It appears that you may have a fairly large gap between your innermost
 >primary turn and the secondary winding.
 >
 >Best regards.
 >
 >-- Bert --
 >--
 >--------------------------------------------------------------------
 >We specialize in UNIQUE items! Coins shrunk by Ultrastrong Fields,
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 >
 >
 >Tesla list wrote:
 >
 >>Original poster: "Peter Lawrence by way of Terry Fritz
 >><teslalist-at-qwest-dot-net>" <Peter.Lawrence-at-Sun.COM>
 >>
 >>Is there a formula for the K (coupling coeff) given that I know the two
 >>resonant frequences that the combined primary plus secondary have.
 >>Here are some example data I collected last weekend,
 >>204.8 KHz primary and secondary resonant frequency, when measured appart.
 >>Then when together at various secondary heights I get:
 >>at 0"     193.42  and  216.10  KHz resonances,  22.8 Hz appart
 >>
 >>at .5"     194.72  and  214.86  KHz resonances,  20.1 Hz appart
 >>at 1"     195.83  and  213.81  KHz resonances,  18 Hz appart
 >>at 1.5" 196.92  and  212.70  KHz resonances,  15.8 Hz appart
 >>
 >>thanks,
 >>-Pete Lawrence.
 >>
 >>.
 >
 >