THE RARE BOOK AND
MANUSCRIPT LIBRARY
OF COLUMBIA UNIVERSITY

Treasures


97 Harold Miller Lewis 1893-1978
Laboratory notebook
Manuscript, 137 p., July 21, 1918-January 8, 1919
While working under the direction of Captain Edwin H. Armstrong (1890-1954) in the Paris laboratory of the U.S. Signal Corps, Corporal Harold M. Lewis kept this notebook in which he recorded the invention of Armstrong's superheterodyne circuit, the basis for most radio, television and radar receivers. On August 13, 1918, Armstrong first explained to Lewis his new short wave amplification system; the complete circuit designs and the first working model were finished between August 14 and September 3, 1918. Thus, Armstrong had created a circuit capable of handling radio signals at much higher frequencies than were then possible. Lewis went on to a career in radio engineering and patented nearly sixty inventions of his own. Armstrong, who during his junior year at the College in 1912 invented the regenerative or feedback circuits, later became Professor of Electrical Engineering and invented in 1933, FM, frequency modulation, the basis for static-free radio reception of high facility.
Gift of Pennie & Edmonds

Collections and Treasures