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Re: Bang the rocks together harder lumpophiles

Hi Bob,

At 12:48 AM 04/22/2000 -0400, you wrote:
>Hi Terry and all.
>
>At the input to the coax you have a discontinuity just before the reflection
>90deg after it 0deg inpractice the  reflection must be spread out a little.
>
>As I have said before its very hard to interpret the time domain signals
>from impulses or edges. Try digitising it and FFTing it with mathcad then
>you have the impulse response which is the transfer function.

Since the signals are only repeated once during the capture and the
digitizing of the scope is high.  The FFT of the single event is probably
too choppy to trust.

http://users.better-dot-org/tfritz/site/misc/Bob12.gif
http://users.better-dot-org/tfritz/site/misc/Ken04.gif

>For those with out such luxuries it  common practice to perform sinewave
>tests on a linear system because superposition holds i.e. you can treat all
>the sine waves independently.  It is not true to say that such tests are not
>applicable to transients. Transients are just a collection of sine waves. An
>impulse has a flat spectrum and an edge has a 1/f spectrum.
>
>I am surprised that your coil characteristic impedance (CI) is so high have
>you confirmed it by
>measurement and at what frequency.  Perhaps its high by the same
>factor the wave is slow compared to a standard TM. The CI will be frequency
>dependent for the same reason the propagation velocity is frequency
>dependent i.e. the turn to turn coupling.  You cant use the  standard
>equation to calculate it just like the propagation time.

Z = SQRT ( L/C )

L = 22.1 mH
C = 9.3 pF
Z = 48748 ohms for the pure T-line equation.

MicroSim can resolve an "average" impedance but that is only some mix of
the probably wildly varying Z along a real coil.  However, MicroSim does
predict loading effects like frequency very well from this number. 


>
>It not a matter of what is realistic its a matter of  taking  measurements
>on parameters like propagation delay.  This can then be used to build a
>model which you can then compare in a realistic case. As you have said the
>standing wave completely dominates the generator signal so its impossible to
>make measurements on it.  The trick of all experiments is setting them up so
>you can accurately measure what you want.
>
>I assume you have been using a standard TM model which is not applicable, no
>turn to turn coupling. Try the one I will send you its only got ten elements
>and only coupling between the stages unlike  a real coil that is coupled
>along its whole length but it should show some dispersion and slow
>propagation.
>

I have studied the capacitance in the x,y and z directions along the coil
but I am not sure I trust those calculations yet.  However, it is very
obvious that a standard T-line model consisting of constant RGLC parameters
is useless.  I think a piecewise model as you elude to is the way to go in
trying to get the measured results to match some type of virtual model or
calculation.  Since the C component is a little negative for about the
first 1/3 of the secondary, the T-line models fail.  However, that
capacitance could probably also be taken as zero without much effect which
would essentially reduce the first 1/3 of the coil to a pure inductor.
Everything points to that being near to the true nature of the thing.

Cheers,

	Terry


>Regards Bob
>
>-----Original Message-----
>From: Tesla List <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
>Date: 19 April 2000 13:58
>Subject: Re: Bang the rocks together harder lumpophiles
>
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