Re: 7.1Hz, how the heck did Tesla succeed?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: William Beaty <billb@xxxxxxxxxx>

On Fri, 15 Jul 2005, Tesla list wrote:

> Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>
>
>  > After all, if you're sending out high power VLF (at hundreds of HZ?),
>  > you can't receive it, since you'd need a quarter-wave antenna 100
>  > kilometers long in order to intercept significant energy from the
>  > fields.  But this objection turns out to be wrong too.  An ideal short
>  > antenna can absorb the same energy flux as a full size quarter-wave
>  > antenna.  That's assuming ideal zero-ohm inductors with infinite Q
>  > tank circuits.  Real inductors make short antennas behave much larger
>  > than their physical length, but not 1000KM large.  But received power
>  > depends on receiver Q, and isn't fixed by antenna length.
>
> That is news to me. Energy has to be collected and the bigger the
> collector....

That's what I thought too.  And I imagined that I had a good understanding
of radio antennas.  But then I stumbled across the subject of
"electrically small resonant antennas."  Totally stunning.  The topic
contains all sorts of concepts that I never encountered in physics texts
or popular reading or even in engineering classes on EM and waves.  Only
certain hams and antenna desginers seem aware of them.  I tried to collect
these together at http://amasci.com/tesla/nearfld1.html and at
http://amasci.com/tesla/tesceive.html  Radio antennas aren't just passive
receivers, instead they're more like sound-cancelling headphones which
absorb energy by emitting out-of-phase radiation which cancels out the
incoming waves.  Here's just one piece:  atoms are roughly 0.1nM in
diameter, they they can strongly absorb light waves where wavelengths are
1000x longer.  How can they do this?  Some sort of QM photon effect?
Nope.  As antennas, atoms are way too small, but it turns out that in some
situations the physical size of an antenna is irrelevant, and the "virtual
shape" of the antenna is a sphere roughly 1/3 wavelength across.  This
effect arises whenever antennas are also resonators.  Hams use this to put
160meter antennas on cars: a tuned resonator is added.  Atoms harness this
same effect: they interact strongly with light because they behave as
high-Q resonators.  Tesla *probably* was using the resonant absorbtion
trick as well, and making his receiving antennas behave as though much
larger than their physical extent.  Though I haven't seen much about the
receivers he planned to use in his "world system."


> I thought received optical power depended on the amount of
> light intercepted (e.g. solar cells to put it into an electrical context).

Yep, but that essentially involves arrays of separate "antennas," not
single dipole antennas.  A piece of black cloth is like an array of
dipoles, and the width of the array is the width of the cloth.  But a
single dipole antenna is different.

Note that a dipole antenna made of fine gauge wire absorbs about as much
RF as a dipole made from wire twice as thick, and if we make a dipole from
wide foil, we don't get proportional gains in energy-absorbtion.  Unlike
with solar cells, the broadside area of the wire does not determine the
energy absorbed.  The "virtual area" of a dipole antenna is relatively
independant of the wire thickness because it depends more on the shape of
the fields surrounding the wire.  In a similar way, the virtual area of
any antenna can be independant of the physical length of the antenna.  If
we can generate phase-locked EM fields which fill the volume around the
antenna out to 1/4 wavelength, then we can create a "virtually large"
antenna, even though the physical antenna is tiny.

Imagine a tiny high-Q coil that absorbs 5KHz radiation for 1/4 wavelength
around the coil.  The antenna would swallow incoming waves that passed
within many kilometers.  Of course the fields at the location of the coil
would be quite intense.  It might pay to use heavily insulated vertical
rod at high voltage, rather than a coil with a volume-filling b-field.


>  > So now what's the objection to Tesla's "world system?"  Tesla failed
>  > to make it work, but that was because wall street turned against him
>  > before it was up and running.  Contemporary experimenters have failed
>  > to power any distant devices via Earth resonance transmission, but
>  > this may just mean that Tesla didn't reveal the necessary details (or
>  > it may just mean that it's difficult to accomplish, and nobody has put
>  > major funding into an attempt.)
>
> I think the onus is on those claiming it _can_ be done to demonstrate it.


That's what this thread is about.  I don't have a big coil myself, but
maybe it will work with a tabletop version.  First question: if we mount a
single-electrode x-ray tube at the top of a big TC, so that the tube is
turning on and off at half the coil's output frequency, does this act as a
HV rectifier?

It might not.  If the ion lifetime is far longer than the pulses coming
from the coil, then the x-rays couldn't produce pulses of conductivity in
the air, and the x-ray tube wouldn't act as a HV rectifier.  (But take
note that the effect would vanish above a certain operating frequency, and
some small coils *might* be too fast, yet a bigger coil might produce
rectification.)

If a coil with an xray tube becomes a DC emitter, what also would go
wrong?  Well, the coil is a short for DC, and the top of the coil is right
near the HV output.  But that just means that the DC HV would vanish
during every half cycle, so there would be no "filter capacitor" effect to
smooth it out.


>  >  >  > Or could he even have made a 60Hz extra coil?  With such low >
>  >  > frequencies a non-resonant air-core transformer could easily be
>  >  driven >  > by mechanical AC generators, and only the "extra coil"
>  >  would need to >  > be resonant.  But the wandering Earth-resonance
>  >  frequency would still >  > be a problem. > > Why should it wander?
>  >
>  > Why should it remain fixed?
>
> Tesla considered the earth to be a spherical conductor of "limited
> dimensions" and those dimensions do not substantially change. The Schumann
> cavity is something I thought wasn't known to Tesla but I may be wrong.

In at least one of his articles he discusses the conductive earth and
ionosphere, and the electrical waves travelling in the gap between them.
But in other articles he talks as if waves of current can move along a
conductor, as if he only needed to drive currents into the earth (but not
also couple currents into the ionosphere.)


> RQ>To accurately paraphrase, they included excitation and resistance losses
> and determined that even
> though the earth is far from "perfectly conducting" it conducts resonate
> current rather well.
>
> The reference to "resonate current" in the commentary is interesting to say
> the least. Current is current in my book.

At resonance a receiver has stronger coupling because it has many chances
to intercept a wave, since the wave passes by it over and over.  It's not
the current that makes the difference, it's the resonance.

> And where is the experimental
> evidence to back up the claim being commented on? I've been holding my 
breath
> on this one for too long.

Agreed.

>  > Corum/Spaniol paper points out, this loss appears across the
>  > transmitter.  It doesn't appear in series between transmitter and
>  > receiver.  All continent-wide power grids have similar losses because
>  > of corona and surface leakage across insulators.
>
> In fact lightning excites the cavity like a giant spark gap.

True.  But the cavity also has a large DC charge, and lightning doesn't
short this out.  Lightning involves fairly small current paths, not paths
between earth and ionosphere.  On the other hand, there certainly would be
some effect since lightning acts as miles-tall conductive strands, and any
RF would heat those strands.  The issue is whether this effect is large or
small when compared to the worldwide vertical leakage caused by the slight
conductivity of air.

> them that they would be doing it somewhere around the last turn of the
> century but........   All I can say is to those who claim it can be done,
> "bring it on".

If many people had figured out this "x-ray tube rectifier" idea, then
perhaps it's already been tried.

Often when a test reveals new phenomena, the people involved will go wild
with publication and publicity ...but when it doesn't work out, they
silently go on to other things.

Either the x-ray thingy has been tried and the failures aren't well
documented...  or perhaps everyone has been thinking in terms of things
like 40KHz Tesla coils, and not in terms of 1KHz pulsed DC transmissions.
I've seen a couple of articles which say that 40KHz is way too high for
earth-resonance power transmission (even 10KHz might be too high.)
Unless the Extra coil was totally gigantic, a magnifier couldn't
reach the low frequencies needed.  That might be what's stopping the
research.



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William J. Beaty                            SCIENCE HOBBYIST website
billb at amasci com                         http://amasci.com
EE/programmer/sci-exhibits   amateur science, hobby projects, sci fair
Seattle, WA  206-789-0775    unusual phenomena, tesla coils, weird sci