Re: Tesla Coil RF Transmitter

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>

Tesla list wrote:

> Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>
> These standing waves may be highly surpressed or eliminated with a 
> large enough top load toroid.  That's why modern coils don't really 
> act as transmission lines and do not act as "slow helical 
> resonators".  They act as "lumped sum" systems and do not exhibit 
> resonant rise to any large degree. I think that's why Tesla designed 
> such a large topload for his Wardenclyffe system.

Well... There is resonant rise, but in the sense of two coupled
oscillators. The rise is not linear, but sinusoidal. If left going,
the energy flows back to the primary. See the waveforms without
"quenching" below:
Primary voltage:
http://www.coe.ufrj.br/~acmq/tesla/vc1910.jpg
Secondary voltage:
http://www.coe.ufrj.br/~acmq/tesla/vc2910.jpg

> The large topload and proper coeff. of coupling (not excessive, ie < 
> 0.18) keep the coil operating at a single freq and prevent freq. 
> splitting which produces the undesireable "transmission line" 
> effects, ie, voltage resonant rise due to the Ferranti effect.

There is always frequency splitting. The waveforms with beats are
always the sum of two sinusoids of different frequencies.

> Older "physics textbook" and other TCs did have standing waves due 
> to their very small toploads.

It's a quite vague concept to mention standing waves in Tesla coils,
where there is more than one frequency in the resonator at any time,
and operation is transient. Standing waves are variations in the signal
amplitude along a transmission line, at sinusoidal steady state.
Something that looks as stationary waves appears over long coils
driven above the main resonance:
http://www.coe.ufrj.br/~acmq/mk95939.jpg
But this happens because, after several cycles of energy transfer,
the voltage along the coil becomes high enough to produce visible
corona in a sinusoidal pattern. The coil is not being excited with
a continuous sinusoid, but by a capacitor-discharge system, as in
a conventional Tesla coil.
If the excitation were continuous, a similar pattern would appear,
really due to stationary waves. Similar, but different phenomena.

Antonio Carlos M. de Queiroz


Antonio Carlos M. de Queiroz