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Voltages used for electric power transmission increased throughout the 20th century. [50] The first "high voltage" AC power station, rated 4-MW 10-kV 85-Hz, was put into service in 1889 by Sebastian Ziani de Ferranti at Deptford, London. [33] The first electric power transmission line in North America operated at 4000 V.
1920: The first regularly operating radio station KDKA goes on air on 2 November 1920 in Philadelphia, USA. It is the first time electronics are used to transmit information and entertainment to the public at large. The same year in Germany an instrumental concert was broadcast on the radio from a long-wave transmitter in Wusterhausen.
The arc converter used an electric arc to convert direct current electricity into radio frequency alternating current. It was used as a radio transmitter from 1903 until the 1920s when it was replaced by vacuum tube transmitters.
A family listening to a crystal radio in the 1920s Greenleaf Whittier Pickard's US Patent 836,531 "Means for receiving intelligence communicated by electric waves" diagram US Bureau of Standards 1922 Circular 120 "A simple homemade radio receiving outfit" taught Americans how to build a crystal radio.
The waveform of 230 V and 50 Hz compared with 120 V and 60 Hz. The utility frequency, (power) line frequency (American English) or mains frequency (British English) is the nominal frequency of the oscillations of alternating current (AC) in a wide area synchronous grid transmitted from a power station to the end-user.
1920s: The Spanish Flu. In the fall of 1918, a mutated version of the virus that claimed its first victims in the spring made its way around the world, causing the death rate to escalate quickly ...
However higher audio frequencies cut through interference better, so in many transmitters the transformer was powered by a motor–alternator set, an electric motor with its shaft turning an alternator, that produced AC at a higher frequency, usually 500 Hz, resulting in a spark rate of 1000 Hz.
However, in the 1920s vacuum tube oscillators replaced it in all these applications. [89] The triode vacuum tube was a much better radio frequency current generator than the noisy, hot, ozone-producing spark, and could produce continuous waves. After this, industrial use of the Tesla coil was mainly limited to a few specialized applications ...