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Re: 7.1Hz, Frequency variation and Q



Original poster: Ed Phillips <evp@xxxxxxxxxxx>

" > Original poster: "Gary Peterson" <gary@xxxxxxxxxxxx>
 >
 >
 > >Original poster: Ed Phillips <evp@xxxxxxxxxxx>
 > >" Might be worthwhile to analize a set of twins to see what
 > >beats they produce.
 > >David E Weiss"
 > >In one of his papers Tesla discusses doing exactly this and says
that
 > >by changing the (relative?) tuning he can produce a large variety of
 > >different sparks.


They'd have to be separate and loosely coupled, no? I wouldn't think the nearly-identical coils could drive the same main terminal. WOuldn't one of them see the other one as a short to ground? I don't know what happens with quarter-wave waveguides, but connecting two parallel resonant RLC tanks together doesn't give beats, it gives 2x lower frequency. If you wanted to inject 100KHz and 100.001KHz into the same antenna, you'd need some sort of big matching network."

	I found the reference.  It's in "Inventions, Researches, and Writings"
[Of Nikola Tesla], Second edition, 1992 Barnes and Noble reprint, pp
202-204.  He starts out by pointing out the difference between the
discharges of his demo coil and that of a static machine.

	"Now compare this phenomenon which you have just witnessed with the
discharge of a Holtz or Wimshurst machine - that other interesting
appliance so dear to the experimenter.  [He previously mentioned
conventional induction coils.]  What a difference there is between these
two phenomena!  And yet, had I made the necessary arrangements, ..... I
could have produced with this coil sparks which, had I the coil hidden
from your view and only the two knobs exposed, even the keenest observer
among you would find it difficult, if not impossible, to distinguish
from those of an influence or friction machine.  This may be done in
many ways .."  He mentions some and then goes on to say "Another way is
to pass through two primary circuits, having a common secondary, two
currents of slightly different period, which produce in the secondary
sparks occurring at comparatively long intervals. ......"  Same point as
Bill raises.

	This same principle is sometimes used in arrangements where as many as
10 or 20 different frequencies, uniformly spaced and phase coherent
(occasionally) can produce much more spectacular but similar effects.
When all of the different voltages add up in phase there is a peak
voltage of N times any of the individual voltages.  Been used to
generate pulsed RF signals and in other "pulse compression" schemes.  I
first noticed this discussion almost exactly 100 years after the
original experiment and at the time I was evaluating a proposed
low-frequency (~30 MHz) radar system which employed 10 different
transmitters so arranged.  Most of the proposed system was fallacious
and based on ignorance of the laws of physics and nature but this
particular part would have worked.

	Of course, just to show the great man wasn't infallible, the same book
in Chapter XXXIII, pp 410-412, describes his proposed rectifier using
only saturable reactors.  I suspect he dreamed up this little gem
without ever doing an experiment......

Ed