Apparently if the transmitter/receiver are smaller than the wavelength used to transmit the energy, and they are located within ~1/4 wave of each other these efficient inductive energy transfers are possible. They are using the 'near-field' effects of EM radiation, not the more commonly used far-field.
See: "Energy sucking antennas":
http://amasci.com/tesla/tesceive.html
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The "energy grabbing" effect is very limited. It's a nearfield effect. It could only operate within about a 1/6- or 1/4-wavelength radius around a coil or capacitor antenna, or in the region between the peaks of a propagating EM wave. In other words, when we add a tuned circuit, we can increase the "effective size" of a tiny antenna until it resembles a half-wave dipole antenna. It usually would be easier to simply build a half-wave dipole in the first place. Normally we would do so.
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Apparently if the transmitter/receiver are smaller than the wavelength used to transmit the energy, and they are located within ~1/4 wave of each other these efficient inductive energy transfers are possible. They are using the 'near-field' effects of EM radiation, not the more commonly used far-field. See: "Energy sucking antennas": http://amasci.com/tesla/tesceive.html " The "energy grabbing" effect is very limited. It's a nearfield effect. It could only operate within about a 1/6- or 1/4-wavelength radius around a coil or capacitor antenna, or in the region between the peaks of a propagating EM wave. In other words, when we add a tuned circuit, we can increase the "effective size" of a tiny antenna until it resembles a half-wave dipole antenna. It usually would be easier to simply build a half-wave dipole in the first place. Normally we would do so. "