100 Years Ago Today

A History Of Events And Happenings From Exactly One Hundred Years Ago

The First Regenerative Circuit

Edwin Howard Armstrong was born in New York City in December 1890. Illness as a child left him withdrawn and he was attracted to engineering. He attended Columbia University and was attracted to the new field of Radio which was in it’s infancy. Tesla had experimented in the 1890 and Marconi copied his work and was beginning to work in wireless transmissions. In 1906 Lee De Forest invented the Audion, a vacuum tube that greatly electrical signals for radio. De Forest made the first ship to shore radio transmission in 1907 and the first public radio broadcast of the opera TOSCA from the New York Metropolitan Opera in 1910. De Forest invented the term “Radio” based on the “radiating signals” of the device.

Armstrong, a 21 year old electrical engineering student, was working at Columbia University’s School of Engineering on the Audion when he realized that he could amplify faint radio signals by repeatedly feeding current through the relatively new Audion grid and boost their power dramatically. This was called Positive Feedback. This was the first regenerative circuit.

On September 22, 1912 Edwin Armstrong made the first successful test of the regenerative circuit. It is revolutionary in the way it amplifies radio waves and promises to make the reception of voice messages without wires a practical, affordable reality.

Original drawing of Regenerative Circuit by Edwin Armstrong

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