'Energy-sucking' Radio Antennas
The Short Version
W. Beaty, Aug 1999

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 partially 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 of KM, or hundreds.)

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 coil 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 one-angstrom atoms 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.

[Comparing the two circuits, w/parasitic capacitance added.]
Fig. 1 Electrically-short dipoles, with and without resonance.

Why 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. Received a 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 wildly.

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