DID TESLA'S WARDENCLYFFE TOWER
GENERATE SQUAREWAVES?
W. Beaty 2008
AN ODD RELAXATION OSCILLATOR
Here's a "lost concept" which I noticed while reading lots of Tesla
material. Suppose we drive a Tesla coil using a low power RF
source which is weakly coupled? And suppose the coil has extremely high
"Q," wound from Litz wire or heavy copper tubing. What happens?
In that case the coil's RF output voltage will ramp up slowly, as if
the oscillating coil was a kind of "capacitor" being charged up. The
Tesla secondary coil is an energy storage component. But it's being
charged up
with AC high frequency, not with DC! Doesn't this mean we can treat
our coil much
like a capacitor? We could discharge it with a very short spark-gap placed
across its terminals. If we kept driving it via loose coupling, this
added spark
gap should start firing slowly and periodically, since the
coil loses half or more of its stored energy each time it's shorted out by
the arc. It ramps up with AC oscillations, then sparks over. It
should go "snap-snap-snap-snap" just like a DC capacitor spark-gap system,
yet it's entirely AC high-frequency.
Here's another odd concept. In the above AC device, suppose we place
a large capacitor in series with that spark gap. Have the discharge drive
a capacitor. What will happen? Usually nothing strange. The AC signal
just thinks the capacitor looks like a good conductor. The capacitor is
invisible to the AC, it just looks like a short circuit for the high
frequency. However, if next we adjust the spark gap so it quenches
quickly, then whenever the gap fires, it will produce a single pulse of
just one polarity, and it will deposit a large DC potential across our
added capacitor. During the spark, the oscillating coil dumps a
half-cycle of a sine wave. A DC surge. Doesn't this mean that we've
invented an early type of rectifier? An 1890s-style AC-to-DC converter?
Without vacuum tube, without silicon! Yes, but I'm just getting started!
:)
To do this, the spark gap would have to quench fast; quench after a
single half-cycle of the ringing (or more easily done: quench after an odd
number of half-cycles.)
In addition, during the next firing of the gap, the capacitor's DC
polarity should reverse! After all, the gap only fires at a large
potential, and if the capacitor had already been previously charged during
the last arc, the gap-voltage will rise to maximum when the instantaneous
coil voltage is opposite to the previous DC polarity still
remaining on the capacitor. So, the gap only fires when the peak-volts of
the AC happens to be backwards.
Therefore, during
each slow triggering of the gap, the capacitor DC polarity is reversed.
As the spark-gap slowly goes snap-snap-snap, the capacitor's DC voltage
goes pos-neg-pos-neg. And most important, the output voltage might not be
too much smaller than the Tesla Coil's HV output. If we built a
multi-megavolt Tesla coil, we could use it to create slow, multi-megavolt
square waves. "Slow" here meaning 10x lower than the coil's resonance
freq, so perhaps 10KHz. Or with
high enough Q, and slow AC ramps, maybe much lower than resonance. 1KHz,
or 100Hz, or even 1Hz. (Or 8Hz. Or sixty!)
By taking a conventional Tesla coil and adding two devices to its
output terminal, one spark gap and one H.T. capacitor, perhaps we can STEP
DOWN the coil's output frequency to a very low value. We still drive it
with
high freq AC as usual, but then it outputs such a low frequency ...that
Nikola
Tesla might call it "electrostatic."
Or, taking a different viewpoint: we've just built a simple sawtooth
relaxation oscillator, but it's a strange variant where both the power
supply and the slow ramp-up are made of AC oscillations, and the output is
not a sawtooth or a brief spike, instead it is a square wave.
NIKOLA TESLA OWNED NO "TESLA COILS"
Where did I get this step-down idea?
Well, think about it: Tesla wasn't working with "Tesla Coils." He
didn't call them that. To us, Tesla Coils are those famous vertical-coil
lightning machines. But to Tesla hinmself they were just one more
electrical component, one more useful tool among many he'd invented.
To him they were just power supplies.
If we have an AC high-voltage power supply kicking around our lab, what
might we use it for? Well, if you're Tesla, you can hook it in series
with a spark gap, then route the enormous discharge pulses through a
resonant circuit. That's right, we can use a Tesla coil as the power
supply for a Tesla coil. Aha, the two frequencies need not be the
same.
But this idea was always there, always obvious, since every classic Tesla
Coil is powered by a sixty-cycle AC resonator: a neon transformer's
secondary
with
a capacitor across it. Hobbyist tesla coil: 60Hz input, MHz output. A
neon sign transformer in parallel
with a 0.05uF capacitor is almost the same as using a 60Hz
tank-circuit as the main power supply! So, why not just use some 200KHz
AC to drive your 100KHz primary coil instead, eh? eh?
:)
So what happens if we actually connected a Tesla Coil as the power supply
for a
very low-freq resonator? Use a TC running at few-100KHz to power a low-freq
long wave VLF spark transmitter? Tesla mentions the parts of the process:
whenever an Extra Coil is driven with CW, its oscillations ramp up over
time,
and if its output is suddenly shorted by a spark gap, brief pulses of
"inconceivable power" are produced. Initially the TC secondary acts like
a tank, like a slowly charging "capacitor." Then it gets periodically
"discharged" by the spark gap. But unlike modern energy-storage caps,
this "AC-storing capacitor" could easily be charged to megavolts, and most
important: it could be recharged over and over again in tiny fractions of
a second.
A TC secondary coil probably has enormous power-processing ability far
beyond that of DC energy storage capacitors ...which is exactly what Tesla
said on numerous occasions!
So Tesla figured out a way to build a Tesla coil where the power supply
operated at megavolt output, and then his large coil at Wardenclyffe
stepped it up from there. Aaaaaaand... the output frequency could be
low.
A SMALL EXPERIMENT
But is this actually real? How about an experiment?
OK, I'll take
this 1" diameter long narrow 800KHz T.C. secondary and drive it from one
end, drive it at
resonance
using my old Wavetek sig gen. It's now behaving like the Extra Coil of a
Magnifier: one end of the coil is driven, and the far end is
left floating.
The Wavetek puts out about 10Vp, and at resonance the far end of the coil
is running at a thousand volts at least. (NE-2 bulbs glow when held
near!) Next I'll
let the extremely tiny sparks from the far end of the coil start leaping
to a "capacitor plate" in the form of a metal object sitting atop a
plastic
block. What happens? Something Very Cool!
A low frequency SQUARE WAVE does appear on the floating metal object.
It's HV
and high-Z, so I monitor it with a nearby scope probe. It's very noisy
and grungy. The cause of this square wave is obvious:
- The 800KHz Extra-coil's output rises to max volts over about ten
cycles.
- the gap sparks over
- after quenching, some DC volts are left on the metal object
- the 800KHz HV ramps up again
- because there's now static HV on the metal object, this time the gap
fires on the OPPOSITE POLARITY of the 800KHz wave
- after quenching, opposite polarity of DC HV is left on the metal
object.
- repeat...
So it's bascially a relaxation oscillator much like a NE-2 blinker.
But this one is powered by AC, not DC. The slow-rising "sawtooth"
waveform is an 800KHz sine with sawtooth modulation, rather than a DC
ramp. And the periodic
pulsing is alternating slow positive and negative current spikes, which
produce
an alternating DC on a capacitor. Wow! Pretty cool, eh?
OK, what if I harness those "slow" alternating spikes? I can use them
to drive a low-freq resonator. Just add a simple tank circuit. I grab an
inductor and capacitor out of the junkbox, connect in parallel, then route
the alternating spikes from the metal object through the resonator and to
Earth connection. Yes! A large slow sine wave appears across this
grounded LC tank. Also, the spark gap's pulses do "phase lock" to the LC
circuit's oscillations, and the signal isn't nearly as grungy as before.
On the scope it remains coherent over more than 50 cycles. It's sort of
like an old hit-and-miss gasoline engine, where the cylinder
doesn't fire
on every single cycle of the piston/flywheel. Makes sense:
the low-freq AC voltage on the resonator is acting backwards through the
circuit and affecting the spark-gap
timing, and it's forcing the gap to fire a bit early: at just the right
time to dump a
single-polarity pulse, and that pulse kicks the next cycle of the slow
sine wave on the resonator. (It's much like a Marconi Spark Transmitter
powered by DC, but here my power supply is a 0.8MHz tesla coil.
Next I examine the component values using an LRC meter, and calculate
that
my junkbox coil/capacitor tank circuit should oscillate at 39KHz. Those
were randomly chosen components. I calculate a better freq: the AC ramp
takes about 10 cycles to rise, and the pulses are half that period, so the
ideal RLC resonator would be... 40KHz?!!!!! But my RLC is 39KHz.
Bizarre. Just by chance those random component values were
perfect. I
love it when that stuff happens. (If I'd grabbed different parts ...would
I have failed? and given up?)
So, I now am the owner of a BACKWARDS TESLA COIL. Its CW sine-wave
input drive is 800KHz, and its output is 20x lower: 40KHz. And this
step-down factor depends on the Q of the Extra Coil, which in this case
was low (it was wound from #40 ga wire.) If instead the
Q-factor of my extra coil had been 10x higher, so that it takes 100 cycles
for the AC HV output to slowly ramp up to the spark-gap voltage, then I
could have stepped the 800KHz down to 4KHz, which would be within the set
of Schumann absorption lines for Earth-resonance. (or, hook it to a
high-Z piezo loudspeaker and hear what it sounds like.)
If Tesla had a huge 75KHz coil of very high Q, then the PRF of his
spark gap and his transmitter output could have been far lower: down in
the hundreds of Hz. The output is an alternating spike waveform, and the
"tank circuit" which supplies the sine wave is ...the entire Earth. As
all
oscillators do, it phase-locks its pulse-drive to its own tank circuit, so
that any changes to the tank circuit's resonant frequency won't de-tune
the driver's pulse-rate. The whole device will just continue
oscillating at the resonant
frequency, even if it's drifting. And so a simple Tesla coil should be
able to excite the
Earth's very low resonances even though the coil's resonant frequency is
tens or hundreds of
times higher. (But note that this "Earth-res phase-lock" effect would
only occur above a certain threshold of operating kilowatts. Those
returning waves in the sky-fields, which are trapped in the Schumann
ionospheric duct, they must be strong enough to bias the next triggering
of the spark gap. If not, then the slow pulsing would be unrelated to
the Earth resonance frequencies, and there would be no coherent
pumping of the Earth-cavity resonator, no "resonant rise" effect.
Hmmmm now, did Tesla have any plans for a giant transmitter where
there was a large, CW-driven "Extra coil," but there was also an
unexplained mysterious "Extra Gap" placed in series with the HV output
conductor?
Yes. Yes he did.
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Regarding Tesla's transmitter at Wardenclyffe NJ, it's still an open
question about how he was able to use a tens-KHz system to drive the Earth
resonance frequencies (which are all below 20KHz, and the best ones far
lower.) To excite the Earth, a huge Tesla coil would have to have far
lower resonance than usual, and therefore be made taller by 20x or 50x
than the largest ones ever built. That, or Tesla would have to have some
way to step the frequency down without reducing the enormous output
voltage.
Perhaps Tesla connected a spark gap in series with his coil's output,
then used this to charge a capacitor? Yes, according to above unpatented
drawings from his collected works, this is exactly what he was working on
during Wardenclyffe years. But nobody has said why that "Extra Gap" was
placed between the main coil output and the capacitive topload hemisphere.
Maybe all of the above has solved a mystery, and the
Wardenclyffe tower was the world's
largest square-wave signal generator?
SQUARE WAVES, AND PHASE-LOCK FEEDBACK TOO
Relaxation oscillators are sensitive to environmental e-fields. After
all, they're being triggered when the voltage across a spark gap reaches a
particular threshold. If other external e-fields are present, these extra
fields
can add or subtract from that threshold. They'll cause the oscillator's
pulses to come earlier or later than normal. (This is why a little NE-2
blinker circuit can detect nearby RF sources.)
If we set up Wardenclyffe to be a square wave oscillator, and then we
leave it outdoors where it can be influenced by other e-fields, perhaps
something very useful will happen. Perhaps the pulse-waves sent outwards
by our system will race all the way around the Earth, then concentrate
themselves in contracting ripples back at our location and cause our
oscillator to fire early.
If such things were to occur, what does it mean? It means that our
device will drive just one of the Earth Resonance frequencies. It means
that if the resonance were to slightly wander because of Solar Wind or
changing magnetosphere phenomena... our transmitter would still remain
locked to that frequency. The system would keep oscillating even as the
frequency drifted up and down. And if we attempted to set our transmitter
to
a much higher frequency, it would leap discontinuously to the
higher
absorption line in the Earth Resonance series. Remember that these
frequencies are all in the audio range. So if the spark gap distance was
made wider and wider, the noise from such a system
would sound like successive notes being struck on a piano keyboard. Or
perhaps sound like an air-raid siren which leaps from note to note. (Well,
they'd
actually be buzzing raspy, spark-gap notes!)
Brrrrrrrrrrr-Baaaaaaaaaaaa-BIIIIIIIIII-BEEEEEEEEEEN! That *may* have
been the characteristic sound of Wardenclyffe tower in operation.
This all solves another Tesla mystery: Earth Resonance frequencies are
known to wander around slowly. For this reason it's supposedly impossible
to strongly excite the Earth Resonances. If your VLF transmitter managed
to hit the target frequency, your success would only be temporary, since
the Earth system would slowly change, and you'd lose the resonance. The
solution is found above: stop treating the Earth as a target frequency for
your drive transmitter, but instead make it part of your oscillator. If
the Earth becomes our oscillator's "Tank Circuit," then such an oscillator
will always be on resonance, even if the frequency-determining components
are wandering in value.
Yes, except for my 800KHz coil test, all this stuff is pure speculation.
But it all hangs together SO NICELY, and explains so many mysteries, that
I thought I'd post the whole mess here on my website and let the critics
have at it.
"I have often been told that my most important results in invention
was
the demonstration of the practicability of transmitting energy over one
wire; because, once we can transmit energy over one wire we can use also
the earth, for the earth is equivalent to a large conductor"
- N. Tesla 1916
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