After graduating from Columbia University, Armstrong works there as a lab assistant and then serves as an officer in the U.S. Army Signal Corps during World War I. While in the army, Armstrong has a brainstorm. He uses Reginald Fessenden’s heterodyne principle to change incoming radio signals to a much lower frequency, where they can be amplified with existing equipment. Armstrong calls his new receiver the superheterodyne; his second major contribution to radio broadcasting.
Edwin H. Armstrong, Radio Pioneer – World War I and the Superhet Circuit
Radio Inquiry Unit