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Re: This phase shift stuff...



Tesla List wrote:

> I already have a 4.25 inch diameter x 26.125 inch coil with about 700+
> turns of #24 on it.  This should be fine for such an experiment.  The
> resonances you menation are well known but the phase differences along the
> coil are the real question.  Is the phase going from 0 to 90 along the
> lenth of the coil as would be the case in a 1/4 wave whip antenna. Or, is
> the phase locked in sync as in the case of standing waves on a string
> musical instrument? 

The phase goes from 0 to 90 degrees along the length of the coil.
But as a vertical coil over a ground plane is a somewhat nonuniform
transmission line, the phase may very in a somewhat nonlinear way.
There is no essential difference in the mechanical analogs.

 A continous wave may develop large standing resonant
> voltages that would not be realistic, but a number of 555 timers and some
> gates should be able to give some pretty close pulses.  Even using a tuned
> primary circuit (at low voltage) and an high frequency amplifier could
> provide a very realisitic signal if experimentation shows the need...

What I suggested was to use a slow square wave oscillator, at a 
frequency of a typical break rate for the coil, controlling a current
source applied in parallel with the primary L1-C1 tank (I). With that
high-impedance current source applied across the primary, the familiar
beat waveforms appear in the primary capacitor voltage, vc1, at all
resonances. The ascii drawing below shows how:

        +-----+----+   o
        |  +  |    |   |
        I vc1 C1   L1  L2
        |  -  |    |   |
        +-----+----+   =
              
Ground the primary for convenience. A current excitation is easier
to implement for low-power tests, as there is no need for an electronic
replacement for the spark gap.

 
Antonio Carlos M. de Queiroz