English: American radio researcher Edwin H. Armstrong and his new invention, the superregenerative receiver in 1922. This was probably taken at the June 28, 1922 meeting of the Radio Club of America in room 306, Havemeyer Hall, Columbia University, New York, at which Armstrong demonstrated the superregenerative receiver. The receiver used only 3 vacuum tubes (visible), but was as sensitive as existing receivers with 9 tubes. However it didn't prove as useful as the other receiver circuits he invented: the regenerative receiver and the superheterodyne receiver, which is used in virtually every radio and television today. The black metal bell (left) is the horn loudspeaker (modern cone loudspeakers hadn't been invented yet), and the wires on the frame (right) is the loop antenna for the radio. The caption of the photo read:

"THE MAN WHO ORIGINATED THE ARMSTRONG CIRCUIT Hertz, Marconi, De Forest - and now Edwin H. Armstrong, head the list of scientists who have made radio, as we know it today, possible. Armstrong has the honor of making three definite contributions to radio. FIRST, he originated the regenerative feedback vacuum tube circuit. SECOND, he originated the super-heterodyne circuit, the most sensitive receiver ever produced. THIRD, he invented the superregenerative receiver, which has just taken the world by storm and which bears his name."