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Re: Lumped vs. T-line - You be the judge...

Hi Bob,

At 01:02 AM 04/22/2000 -0400, you wrote:
>Hi all,
>
>I suspect as previously posted that high frequencies travel with a velocity
>calculated by the standard transmission line equations.  Very high go even
>faster and at low frequencies when the inductive coupling is in opposition
>to the wave travels slowly. So the harmonics of your signal get to the
>end first. A standard non dispersive transmission line does not have this
>property and hence the edges remain intact. It just occurred to me that
>if the distributed L and Cs are not constant this may also disrupt the
> edges. I can not account for the initial pulse possibly interturn C
>but the maths don't support it or If you use very low C probe or poor
>scope you may get an initial pulse connected to anything in the room.
>A good trick is connect the probe tip to the ground point but keep
>everything else the same you may be surprised how large a signal you
>get.

I shorted the probe tip.  Even at the scope's highest gain setting, the
voltage reading remained at dead zero with the tip shorted.  The scope is a
TEK TDS210 and the Probe is a P6009 high voltage RF type.

>
>
>When one end is shorted and the other is open it does have similar
> behaviour to a lumped tuned circuit at least at one point . But unlike
>a tuned circuit it resonates at 1,3,5,7..etc. frequencies so when you
>apply a transient you get the sum of each of the resonances but the
>dispersion makes it look different than a non dispersive line.
>
>Using a switched sinewave other experimenter/s have confirmed a
>1/4 cycle delay at the resonance frequency and 1/8 half a long the coil.
>It has also been show how the amplitude builds with each reflection
>from the end.

I question the effects of the probe loading there.  Although, the graph i
lucked on capturing at:

http://users.better-dot-org/tfritz/site/misc/Ken05.gif

Does tend to support this.

I am starting to think the secondary looks like a pure inductor in series
with a small transmission line at the high voltage end where the high
energy storage takes place.

>
>.Could somebody please measure the propagation delay with
>sinewaves at the resonant frequency and at say x2 X3 X4 X5
>and X10 and X100 so the dispersion constant can be determined.
>
>You could also try the L coupled model I am sending to Terry.
>The model assumes a constant distribution of C which could easily
>be changed. The fact that most transmission line models have
>constant parameters along there length does not invalidate the
>concept but in any case they dont have the dispersion due to the
>coupled L.

I will check out this model.

Cheers,

	Terry

>
>Well we atleast we concluded  the phase issue.
>
>Regards Bob
>