Re: Hybrid Coil (was Coil Efficiency)

From: 	Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: 	Thursday, July 31, 1997 3:33 PM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: Hybrid Coil (was Coil Efficiency)

Hi Greg,

> From:   Greg Leyh[SMTP:lod-at-pacbell-dot-net]
> Sent:   Wednesday, July 30, 1997 11:10 PM
> To:     Tesla List
> Subject:    Hybrid Coil (was Coil Efficiency)

> >     The theory: Using easily accessible mechanical analogy of the
> > steel ruler in the vise and varying "coupling" height and noting
> > effects on ruler movement, and looking at the concept of link
> > coupling into a transmission line, it seems to me that what in effect
> > we are doing is _tapping_ into the line at some way along its length
> > (this applies to 2 coil systems only). Now if you do this in a
> > transmission line, you are tapping into a particular impedance (with
> > a particular impedance) since this is different along all portions of
> > the line.
> A very compelling theory, and observation!  That may explain an interesting
> thing that happens in PSPICE, when you try to turn a standard coil into a
> 3 coil magnifier.  
> If in PSPICE an appropriate capacitor (7.5 nF for my coil) is 
> connected
> across the lower 1/12 of the secondary on a standard coil, then the
> operation of the coil is almost identical to that of a magnifier, according
> to PSPICE.  This is because the K values between the primary and the lower 
> 1/12 of a secondary of a typical coil are around 0.4, whereas coupling to 
> the upper 1/12 may be less than 0.01.  The point where the 7.5nF cap is
> connected defines exactly where the 'tap' is along the secondary.
> I propose calling this arrangement a 'hybrid coil', as it is not a pure 2 coil
> system (due to the secondary tap) nor a 3 coil magnifier (finite coupling exists
> between the primary and 'free resonator').

How did you determine the value of the capacitor? (guess - Xc gives a 
resonant condition at natural Fr for the 1/12 portion of the line?). 
I've got to try this.