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Re: That secondary behaviour, E-Tesla5, and Corum's thing...
Tesla List wrote:
> Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
> What height to width ratio would you be interested in? My coils are pretty
> conventional but perhaps I could dig something up. I think the lower
> harmonic frequencies are caused by the fact that the very top of the coil
> looks like a capacitor since it charges the large area at the top of the
> coil.
Possibly. The inductance per unit of length is also smaller at the ends
of the coil. If measurements are made at the top, the added capacitance
will also shift the frequencies. I made my tests with a coil with 3.5"
of diameter and 12.5" of length. The same effects shall appear in any
coil, but I would expect more deviation from the TEM transmission
line in short coils.
> E-Tesla5 used to have trouble with bare coils until I programmed in the
> corresponding voltage distribution for this and that fixed it right up.
The ideal would be to make the program compute what is the correct
voltage distribution. Somewhat more complex, I imagine, because for
this the fields can't anymore be considered static.
> I would suspect that a very long thin (like 4 feet long 1 inch dia) coil
> would have a very small top capacitance and hit the Fo, 3Fo, ...
> frequencies much more accurately. Is that what you are trying to check?
I agree. The old experiments mentioned by Fleming used a coil parallel
to the ground. A vertical coil changes the distribution of the
capacitance
to ground along the coil, and shall produce greater deviations.
I will try to repeat my experiments, observing with more details what
happens. I used a rather unusual method to excite the base of the coil,
after verifying that with a sinusoidal signal generator I was not
observing clearly the high-order resonances. I connected a primary
circuit also, with shorted gap, excited it with a low-frequency square
wave current source in parallel, and tuned it to the resonances of the
secondary, searching for the characteristic beat waveforms over the
low-impedance primary. This results in waveforms similar to what is
seen in a capacitor-discharge system, but with all the waveforms
integrated.
> I have some big terminals :-) I'll see what I can come up with. My
> longest coil is only 6.14 aspect ratio. Would that work or does it REALLY
> need to be long and thin?
The effect will appear.
Antonio Carlos M. de Queiroz