Ernst Frederick Werner Alexanderson (Swedish: [ɛʂnt alɛkˈsandɛʂɔn]; January 25, 1878 – May 14, 1975) was a Swedish-American electrical engineer and inventor who was a pioneer in radio development.

Alexanderson also created the amplidyne, a direct current amplifier used during the Second World War for controlling anti-aircraft guns.

[3] He studied at the University of Lund (1896–97) and was educated at the Royal Institute of Technology in Stockholm and the Technische Hochschule in Berlin, Germany.

He emigrated to the United States in 1902 and spent much of his life working for the General Electric and Radio Corporation of America.

Alexanderson's family were convinced the huge spinning rotors would fly apart and kill him, and he set up a sandbagged bunker from which to test them.

In the summer of 1906 Mr. Alexanderson's first effort, a 50 kHz alternator, was installed in Fessenden's radio station in Brant Rock, Massachusetts.

In 1930, he conducted an early public demonstration of his large screen television system on a closed-circuit channel at Proctors in Schenectady.