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Considering the service performed by Armstrong, and his standing among his men and superior officers, this memo must have been hard to send -- as well as receive.

Armstrong would apply for a French patent on his second great invention, the superheterodyne circuit, in December of 1918. He would apply for a U.S. patent in February of 1919 (issued in June of 1920, #1,342,885). However, as would happen to Armstrong time and again, the story does not stop there. His U.S. patent was overturned by the U.S. District Court of Appeals of the District of Columbia in December of 1928. A Frenchman, Lucian Levy, would be judged to have disclosed the basic principals of the circuit in 1917.
So why do so many consider Armstrong to be the inventor of the superheterodyne circuit? Walter Shottky may have stated it best in 1926: "The "word" seems, at any rate, to have been far less important than the "deed," and there appears to be no doubt that it is Mr. Armstrong and his collaborators to whom we owe the deed, which has made the super-heterodyne method such an invaluable instrumentality in radio engineering." (Must reading is "Who Invented the Superheterodyne?" by Alan S. Douglas, The Legacies of Edwin Howard Armstrong, published by The Radio Club of America, 1990.)

Documents pertaining to Armstrong's French patent application.

Armstrong, General Ferrie and Professor Abraham in front of the Eiffel Tower, 1918.