Alexanderson alternator

Alexanderson alternator
200 kW Alexanderson alternator preserved at the Grimeton radiotelegraphy station, Sweden, the only remaining example of an Alexanderson transmitter
Classification	Alternator
Industry	Telecommunications
Application	Signal transmission
Inventor	Ernst Alexanderson
Invented	1904 (120 years ago) (1904)

An Alexanderson alternator is a rotating machine, developed by Ernst Alexanderson beginning in 1904, for the generation of high-frequency alternating current for use as a radio transmitter. It was one of the first devices capable of generating the continuous radio waves needed for transmission of amplitude modulated (AM) signals by radio. It was used from about 1910 in a few "superpower" longwave radiotelegraphy stations to transmit transoceanic message traffic by Morse code to similar stations all over the world.

Although superseded in the early 1920s by the development of vacuum-tube transmitters, the Alexanderson alternator continued to be used until World War II. It is on the list of IEEE Milestones as a key achievement in electrical engineering.^[1]