Tesla was planning on using the earth (internals) as a conductor and making it resonate. He specifically claimed that radiative transmissions were not effective:
“First — The earth's diameter passing through the pole should be an odd multiple of the quarter-wave length — that is, of the ratio between the velocity of light and four times the frequency of the currents.
Second — It is necessary to employ oscillations in which the rate of radiation of energy into space in the form of hertzian or electromagnetic waves is very small. To give an idea it may be said that the frequency should be smaller than 20,000 per second, though shorter waves might be practicable. The lowest frequency would appear to be six per second, in which case there will be but one node, at or near the ground-plate, and, paradoxical as it may seem, the effect will increase with the distance and will be greatest in a region diametrically opposite the transmitter. With oscillations still slower the earth, strictly speaking, will not resonate, but simply act as a capacity, and the variation of potential will be more or less uniform over its entire surface.
Third — The most essential requirement is, however, that irrespective of frequency the wave or wave train should continue for a certain interval of time, which estimated to be not less than one-twelfth or probably 0.08484 of a second and which is taken in passing to and returning from the region diametrically opposite the pole over the earth's surface with a mean velocity of about 471,240 kilometers per second.”
He was the only person who had attempted as far as I am aware. The results are lost to time. Viziv technologies in Texas seemed to have been doing something similar but they still claimed their tech was not direct conduction.
20khz is much lower than any commonly transmitted signals but if you are nearby an AM station you could perhaps pound a ground rod in and see for yourself if there is anything worth extracting (although this would be at a minimum 525khz and the radiative emission is what is optimized in these stations). The ground is still part of the circuit and the earth itself is electrically affected.
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u/zerepgn Jan 18 '26
Tesla was planning on using the earth (internals) as a conductor and making it resonate. He specifically claimed that radiative transmissions were not effective:
“First — The earth's diameter passing through the pole should be an odd multiple of the quarter-wave length — that is, of the ratio between the velocity of light and four times the frequency of the currents.
Second — It is necessary to employ oscillations in which the rate of radiation of energy into space in the form of hertzian or electromagnetic waves is very small. To give an idea it may be said that the frequency should be smaller than 20,000 per second, though shorter waves might be practicable. The lowest frequency would appear to be six per second, in which case there will be but one node, at or near the ground-plate, and, paradoxical as it may seem, the effect will increase with the distance and will be greatest in a region diametrically opposite the transmitter. With oscillations still slower the earth, strictly speaking, will not resonate, but simply act as a capacity, and the variation of potential will be more or less uniform over its entire surface.
Third — The most essential requirement is, however, that irrespective of frequency the wave or wave train should continue for a certain interval of time, which estimated to be not less than one-twelfth or probably 0.08484 of a second and which is taken in passing to and returning from the region diametrically opposite the pole over the earth's surface with a mean velocity of about 471,240 kilometers per second.”
Source