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Re: magnifier vs. classic tc (magnifier modeling) (fwd)
---------- Forwarded message ----------
Date: Sun, 29 Mar 1998 15:12:47 -0800
From: "Antonio C. M. de Queiroz" <acmq-at-compuland-dot-com.br>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: magnifier vs. classic tc (magnifier modeling) (fwd)
John Freau wrote:
> I did a little more work with the small magnifier setup. It turns out
> that the behaviour (beat appearance-wise) is actually
> the same with or without the point
> installed onto the toroid (I turned up the power slightly, and this
> may have made the difference now). The setup gives best spark
> output with the secondary variable cap set at about 68pF, this is
> the adjustment that gives what looks like one long (30uS) RF beat. BTW,
> I've tried various positions for the pickup probe to the scope, cleanest
> signal results from just placing the wire on the floor between driver
> and resonator, I think this is picking up primarily the secondary output
> waveform.
The best point to see exactly what is happening would be at the top of
L2. Maybe you can add a large grounded capacitor in series with the variable
C2, forming a capacitive divider with it, and measure the voltage over it
with a direct connection (with some overvoltage protection).
> If I set the variable cap at 78pF (it used to give these short beats when
> tuned to 164pF, so it changed now, maybe due to the slightly hower power,
> and greater spark loading...have to check it all again) to
> give a short 5.6uS beat, then the
> sparks are a little shorter and quench is poor at the 6th RF beat notch.
> This poor quenching is probably what is making the sparks shorter with
> this adjustment. To benefit from a tight effective coupling, it is
> necessary to be able to quench at one of the early notches, which so
> far, I cannot do with this system. I may try raising the break-rate to
> increase the spark loading to see if this helps, but in general it's hard
> to properly quench these small systems.
Are you measuring these notches at the primary of secondary side? The
correct point would be the primary, as the waveforms at one or other sides
can be very different. Deep notches at the primary side would indicate
the best tuning.
> Another thing I've noticed is that if the adjustment is made that gives
> the 5.6uS beats, these beats seem to lose their *harmony* after
> awhile (along the quenching waveform seen on scope), and the notches
> become less deep after a number of them occur (within one bang)
> and this may be degrading the quenching also. In contrast, if I set
> things so I obtain the long (30uS)) beat, deep notches begin to form
> near the end of the beat, which may help the quenching. Maybe if
> I adjust the driver k, a point may be found that will improve the nature
> of these beats over the entire firing duration. (I.e. magic value utilization
> may help.)
This is probably caused by the presence of three oscillatory modes, with
two at very close frequencies. Beating waveforms appear to change slowly
with the period of the beat between the two close frequencies.
> It was also observed that the best spark output seemed to occur
> when the after-quench beats were of the longest possible (100us?)
> duration. It was difficult to measure these beats because of their
> shimmering, interwoven appearance.
This is expected. The longest beat period corresponds to the best
energy transfer from C2 to C3.
Please, when reporting experiments list again the specifications of the
system being measured. Simplifies a lot the work of someone searching
for data in the archives.
Antonio Carlos M. de Queiroz
http://www.coe.ufrj.br/~acmq