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Updated: May 28, 2025
The sending apparatus was so arranged that continuous oscillations are set up in the ether, either by a high-frequency machine or from an electric arc. Where set up by spark discharges the spark frequency must be above twenty thousand per second. This unbroken wave train does not affect the telephone and is not audible in a telephone receiver inserted in the radio receiving circuit.
Under the sub-caption of Self-induction and Inductance in the beginning of this chapter it was shown that it was the inductance of a coil that makes a current flowing through it produce a strong magnetic field, and here, as one of the constants of an oscillation circuit, it makes a high-frequency current act as though it possessed inertia.
In theory it was a condition of the space just outside one surface of a sheet of metal. It was like that conduction-layer on the wires of a cross-country power-cable, when electricity is transmitted in the form of high-frequency alterations and travels on the skins of many strands of metal, because high-frequency current simply does not flow inside of wires, but only on their surfaces.
It consists of a thin platinum wire through which the high-frequency currents surge and these heat it; the expansion and contraction of the wire moves a needle over a scale marked off into fractions of an ampere.
Five feet, ten, with the slant of the floor giving him added impetus.... Then his muscles tightened convulsively. A wave of pure agony went through his body. He dropped and lay writhing on the floor, while the high-frequency currents of an induction-screen had their way with him. He was doubled into a knot by his muscles responding to the electric stimulus instead of his will.
"It is what the dancing pithballs of Franklin's time were to the multipolar, high-frequency dynamo. But if we could control this force and handle it on a large scale we could do anything with it destroy the world, drive a car against gravity off into space, shift the axis of the earth perhaps!"
Soft iron cores are not used in oscillation inductance coils and oscillation transformers for the reason that the frequency of the current is so high the iron would not have time to magnetize and demagnetize and so would not help along the mutual induction to any appreciable extent. High-Frequency Currents.
Under the sub-caption of Self-induction and Inductance in the beginning of this chapter it was shown that it was the inductance of a coil that makes a current flowing through it produce a strong magnetic field, and here, as one of the constants of an oscillation circuit, it makes a high-frequency current act as though it possessed inertia.
It was with this in mind that I later chose for my Ph.D. thesis a piece of experimental research on the uses of high-frequency electric currents. During my subsequent years of stuffy, however, I found myself no nearer an answer to the problem that haunted me. All that I experienced, in scientific work as in life generally, merely gave it an even sharper edge.
The resistance of a circuit to high-frequency currents is different from that for low voltage direct or alternating currents, as the former do not sink into the conductor to nearly so great an extent; in fact, they stick practically to the surface of it, and hence their flow is opposed to a very much greater extent.
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