experimental radio wave detector

experimental radio wave detector

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This is the main section of Edwin Howard Armstrong's first regenerative radio circuit, constructed in late 1912 while he was a student at Columbia University. On top is a vacuum tube called an "Audion" made by Lee DeForest. Armstrong's research into the Audion's electrical properties led him to a fundamental discovery. He could wire the tube in such a way as to feed the weak received signal back into the circuit. This "regeneration" of the signal resulted in receivers that could detect distant signals and then amplify them so that they could be heard without headphones.
The invention of radio first involved the transmission and receipt of telegraph dots and dashes rather than voice, hence the term “wireless telegraphy.” The signals tended to be weak and required the operator to wear headphones to hear the signal. Edwin H. Armstrong invented a circuit that allowed people to hear distant radio transmissions without headphones. He built this device around a commercially-available DeForest “Audion” tube in 1913, while a student at Columbia University. The circuit also increased the sensitivity of the receiver and Armstrong received signals from Clifden, Ireland, San Francisco and Hawaii.
Object Name
Radio Wave Detector
radio receiver
Other Terms
Radio Wave Detector; Radio
Date made
associated date
associated user
associated person
Armstrong, Edwin Howard
Armstrong, Edwin Howard
overall: 17 in x 8 1/2 in x 8 1/2 in; 43.18 cm x 21.59 cm x 21.59 cm
ID Number
catalog number
accession number
Credit Line
from Marion Armstrong
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Work and Industry: Electricity
Inventing in America
Exhibition Location
National Museum of American History
Data Source
National Museum of American History
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