Radio receiver crude triode, was invented in 1906 by Lee De Forest as a more sensitive detector for radio receivers, by adding a third electrode to the thermionic diode detector, the Fleming valve. It was not widely used until its amplifying ability was recognized around 1912. The first tube receivers, invented by De Forest and built by hobbyists until the mid 1920s, used a single Audion which functioned as a grid-leak detector which both rectified and amplified the radio signal. There was uncertainty about the operating principle of the Audion until Edwin Armstrong explained both its amplifying and demodulating functions in a
Harold Rosen (electrical engineer) Harold Rosen (electrical engineer) Harold A. Rosen (March 20, 1926 – January 30, 2017) was an American electrical engineer, known as "the father of the geostationary satellite", and "father of the communications satellite". He formed and led the team that designed and built the first geosynchronous communications satellite, Syncom, for Hughes Aircraft Company. Rosen served in the US Navy as a radio communication and radar technician during World War II. He graduated from Tulane University in 1947 with a Bachelor of Engineering degree in electrical engineering. He received his M.S. (1948) and Ph.D. (1951) in electrical engineering from the California