The work of Hertz and his successors : being a description of the method of signalling across space without wires by electric waves / by Oliver Lodge.

Oliver Lodge

Date:: [1897?]

Credit: The work of Hertz and his successors : being a description of the method of signalling across space without wires by electric waves / by Oliver Lodge. Source: Wellcome Collection.

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$A closed circuit such as this is a feeble radiator and a feeble absorber, so it is not adapted for action at a distance. In fact, I doubt whether it will visibly act at a range beyond the j\ at which true radiation of broken-off energy occurs. If the coatings of the jar are separated to a greater distance, so that the dielectric is more exposed, it radiates better ; because in true radiation the electrostatic and the magnetic energies are equal, whereas in a ring circuit the magnetic energy greatly predominates. By separating the coats of the jar as far as possible we get a typical Hertz vibrator (Fig. 5), whose dielectric extends out into the room, and this radiates very powerfully. Fig. 5.—Standard Hertz Radiator. Ordinary Size Hertz Vibrator. In consequence of its radiation of energy, its vibrations are rapidly damped, and it only gives some three or four good strong swings (Fig. 1). Hence it follows that it has a wide range of excitation ; i.e., it can excite sparks in conductors barely at all in tune with it. The two conditions, conspicuous energy of radiation and persis- tent vibration electrically produced, are at present incompatible. Whenever these two conditions coexist, considerable power or activity will, of course, be necessary in the source of energy. At present they only coexi!=it in the sun and other star?, in the electric arc, and in furnaces. Two Circular Vibrators sparling in sympathy. The receiver Hertz used was chiefly a circular resonator (Fig. 6), not a good absorber but a persistent vibrator, well adapted for picking up disturbances of precise and measurable wave-length. Its mode of vibration when excited by emitter in tune with it is$