Re: slow-wave helical resonator

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Gary,

On 18 Aug 2002, at 22:06, Tesla list wrote:

> Original poster: "Gary Peterson by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <glpeterson-at-tfcbooks-dot-com>
> 
> > It took about five minutes with an oscilloscope to find out that this
> > recipe doesn't work for anything. In treating the pri-sec system as a
> > master oscillator, the assumption is made that the primary is driven
> > by a voltage source and that the pri-sec behaves like a voltage
> > source. Unfortunately, neither is true. The primary is driven by a
> > charged capacitor which runs down as energy is transferred, and
> > coupling constant between primary and secondary of less than 1 or
> > close to it also causes the system to deviate from the properties of
> > a voltage source.
> 
> When following the recipe did you look at the RF energy distribution with
> your spectrum analyzer?

No. Observing in the time domain was enough to see where the major 
resonance was occurring (which was nowhere near where Tesla said it 
should have been). I tried several times with different coils wound 
to the 1/8wave - 1/4wave recipe and was disappointed. Then I simply 
tuned the driving generator and hunted for the main resonance. I 
found that for coils *in general* i.e. not built specifically to Dr 
de Queiroz's recipes to transfer all energy to the resonator alone, 
the system behaved more-or-less as though the secondary and resonator 
formed a single entity.

      One interesting thing I noted was that Tesla's coaxial 
arrangement of pri-sec and resonator was far from ideal. There was 
significant coupling (about 0.06 from memory) between them and 
powered testing yielded poorer results than when the resonator was 
moved beyond the pri-sec system (Golka's idea I understand). I found 
this when I built a scale model of the CS machine (or one of its 
variants). This result was later supported by running MandK on the 
setup to calculate rather than measure the coupling.

  Tesla described a modification of the basic
> magnifying transmitter circuit that would also be interesting to look at.
> In each case the object appears to be getting a narrow signal at the
> resonant freq. of the e-coil.

I know that's what he was trying to do. Aside - I've never been able 
to see the point of stuffing all energy in the resonator alone (apart 
from the fact that it is a neat trick) because to do so would place 
the entire voltage burden across it and it still has to obey the same 
constraints as any other coil. In other words, it is no more immune 
to flashovers when driven this way than as the resonator in a 2 coil 
setup (save perhaps that it is no longer in close vicinity to the 
primary and hence electric field aberrations due to that won't occur 
near the base to the same extent).
 
> Colorado Springs
> Sept. 18, 1899
> Experiments were resumed with all transformers in place, HIGH SPEED BREAK
> and connection in multiple arc of West. Transformer. The object was to
> further test the intensity of the vibrations produced particularly WITHOUT
> SPARK. The connection was as in diagram.
> 
> www.tfcbooks-dot-com/mall/more/images/csn_p189.jpg
> 
> It was though that in this arrangement, which was dwelt upon before, the
> DISTURBANCES were produced more economically than when using a spark
> discharge. The experiments fully confirm this.  In the tests the capacity of
> the two balls of 18" diam. did not very materially derange the adjustment
> and period of the circuit.  This is to be expected; as for the secondary the
> capacity was far too small and on the other hand the INDEPENDENT VIBRATION
> OF THE EXTRA COIL could not be materially interfered with since the
> condenser formed by the two balls and zinc plate allowed free passage of
> currents to earth.  Now the important thing was to decide whether it is
> better to make length of extra coil one half or one quarter of wave as
> before. This to be thoroughly investigated.  THE WORKING WAS EXCELLENT WITH
> 1/4 WAVE LENGTH.

I shall have to dig out my copy of the "Notes" yet again. I have 
absolutely no doubt that the efficiency was higher - leaving the gap 
out alone would do it. There is much speculation and supposition in 
this piece as there is in much of the works. I don't blame Tesla for 
that. He didn't have access to the kind of instrumentation that we 
do. In particular, that assertion about interference doesn't hold 
water because of the coupling I mentioned earlier. For an upright 
coil, 1/4 wave is its dominant mode and the higher the ratio of extra 
to secondary inductance is, the closer one gets to operating at the 
1/4 wave resonance of the extra coil alone in a magnifier 
configuration. 

     It should be noted a hundred years later, we have been able to 
formulate design rules way in advance of anything Tesla had available 
as evidenced by the fact that we only have to have one go at 
designing and building a coil instead of many to end up with a well 
working system.

Regards,
Malcolm