'Energy-sucking' Radio Antennas
Go out and build yourself a dipole antenna to gather EM waves. If your
antenna is "electrically short," meaning that the length <<
wavelength, then what happens if you use this receiver to *transmit* a
cancelling wave which is
phase-locked to the incoming waves you wish to absorb? This
cancels the energy in a significant part of the nearfield region of your
antenna. Since the antenna is so small, it does not radiate much EM, so
the effect seems to apply only to the nearfield region. At low
frequencies this region can be enormous, kilometers in diameter. (Or tens
KM, or hundreds.)
The Short Version
W. Beaty, Aug 1999
But this is impossible! Energy cannot simply vanish! You are correct sir.
When the "cancelling wave" has grown to an instantaneous maximum, the
antenna is "sucking"
a poynting-flow out of the entire nearfield region surrounding itself. The
intense AC electromagnetic fields generated by such an antenna act as a
type of enormous "virtual EM funnel." By manipulating the e- and b-fields
of the nearfield region separately, we can change the power and hence the
effective area of the receiving antenna. For example, by actively
increasing the b-field surrounding an electrically small loop-antenna,
(and leaving the e-field alone,) we can hugely increase the rate of
EM energy being intercepted by the antenna. Or, do the same with a short
dipole, by increasing its e-field.
What's really cool is that these are passive devices, with no active
transmitter system needed. Any resonant
circuit of extremely "high Q" will build up the desired
phase-locked, active-cancellation field and become an "energy sucker."
This only ocurs if we use components which allow the fields within the
and/or capacitor to couple with the surrounding volume. A large square
loop-antenna built using large-diameter copper plumbing pipe would make an
excellent low-resistance coil. Superconductor vacuum-capacitors and coils
would be all the better. Or instead just extend a short whip-antenna from
your hi-Q tuned circuit and connect the other terminal to ground, and
you'll see an immense AC voltage appear on the antenna as the "virtual
funnel" extends itself and begins to suck energy out of the weak ambient
fields of whatever distant transmitter to which you've tuned the system.
In physics, the effect is hidden within the concept regarding the
"collision crosssection area" of particles. These areas change as the
particle-energies approach certain resonant absorbtion values. The size
of your "Barn" dance can vary wildly depending on whether your music is
"in tune." :)
This isn't just high-energy particle physics, either. At resonance, a
1-angstrom atom can spread its field-nets outwards to 3000 angstroms and
punch a vast hole in the propagating light waves at 6000 angstrom
frequencies. For example, that's why sodium gas is so opaque to the
sodium-line spectrum, even though the individual atoms in the gas present
almost no cross-section to the incoming waves. The sparse gas of
behaves like a bag full of 3000A-diameter black spheres. (And perhaps it's also why
sodium bose-einstein-condensates can slow light down to a
propagation-speed similar to that of "heat conduction.")
In theory these concepts allow us to steal power from both AM antenna
towers and distant 60Hz power lines, or transmit kilowatts from tiny
desktop antennas, and perhaps explain the human hearing system and ball
lightning, or build portable AM radios which need no longwire antennas...
and also communicate usable power to planes, trains, and automobiles
through a sort of, ahem, "World System" VLF radio-energy distribution
apparatus which lets us employ extremely feeble RF fields as the transfer
medium for energy-flows greater than anyone could possibly suspect. The
*receivers* develop the intense EM fields, and this eliminates any
requirement that we transmit high-power radiation.
This stuff has always been around, but in my opinion modern
engineering is partially clueless about it. Physics appears to be the
same. The topic seems to be an overlooked hole in physics which leads to a
relatively unexplored realm. How does an atom actually absorb a photon,
what is the detailed mechanism and time-sequence? Observe stimulated
emission in radio circuits, or even at DC. Make giant desktop atoms which
do things real atoms do (perhaps even exhibit chemical bonds?) Make model
biomolecules, and perhaps notice some phenomena overlooked by chemists.
is EM resonance so odd? I always knew this , but when I had an epiphany
regarding all this stuff, I finally met the full weirdness head-on.
serious case of brain-burn. (So what else is new?)
In electrical engineering, this topic is known as "EM of cavity
probes." Searching in physics papers only turns up discovered only two so far, both of which
were written in the 1980s. And one is by my hero Dr. "Beer-Clouds"
Bohren. If Chris Bohren has noticed this topic, then my alarm bells ring
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