On the night of 30 January 1914, Edwin Howard Armstrong, accompanied by Professor Morecroft from Columbia University, demonstrated his regenerative receiver to David Sarnoff and Roy Weagant of The American Marconi Company at the Belmar receiving station then under construction.Regenerative detectors, the part of a radio that actually removes the audio or other intelligence (modulation) from the radio waves, are one of the oldest circuits invented; Armstrong patented the regenerative detector in 1913. A modern fan offers this version of the schematic:
triode) vacuum tube (V1 in this schematic) was new and high tech, having been invented in 1906 but not really understood. One of the first discoveries made about vacuum tubes was when Thomas Edison noticed that current would flow in a wire on the outside of the glass envelopes of the two-element (diode) tubes of the day. In what strikes me as strange for the man, Edison was not the first one to take advantage of the The "Edison effect". The man who first tried putting the wire inside the tube was Lee DeForest, who found applying a negative voltage to this screen controlled the flow of current in the tube. It was named the control grid and the "DeForest electron valve" became the first electronic device capable of amplification. By adjusting the distance (and coupling) between L3 and L1/L2, the gain of the amplifier could be adjusted until just before it broke out into oscillation, so that any increase in signal made it start to oscillate. At this point, it had maximum gain, and the Armstrong's detector was more sensitive than any existing receiver.
Suddenly mankind had a way to communicate instantly over long distances without running wires - or running on foot!
Edwin Armstrong and David Sarnoff began a very complex relationship here. Armstrong was the epitome of the genius inventor. Essentially all of modern radio communications came out of Armstrong's mind. Within a few years, 1918 - at the end of WWI, he invented the superheterodyne technique for receivers, and that basic approach is still used in the vast majority of radios in the world. The invention he is probably best known for, though, is Frequency Modulation in 1933.
Sarnoff, on the other hand, was an "inspector" for the American Marconi Company in 1914, but by the 1930s was the head of the Radio Corporation of America, RCA. If anything, he was the epitome of the "hard-driving sonofabitch". His patent fights against Armstrong consumed the inventor's life and it is widely thought that his frustrations with his legal patent fights with Sarnoff ultimately led Armstrong to his suicide in 1954. Ironically, his death was January 31st, 40 years after the demonstration of the regenerative receiver - almost to the day. The story of these two men has been told in the book "Empire of the Air: The Men Who Made Radio", which also led to a PBS documentary based on the book. It's a captivating, fascinating story, which I can't do justice to here.