Editing Edwin Howard Armstrong (section)

==FM radar==

During World War II, Armstrong turned his attention to investigations of continuous-wave FM radar funded by government contracts. Armstrong hoped that the interference fighting characteristic of wide-band FM and a narrow receiver bandwidth to reduce noise would increase range. Primary development took place at Armstrong's Alpine, NJ laboratory. A duplicate set of equipment was sent to the U.S. Army's Evans Signal Laboratory. The results of his investigations were inconclusive, the war ended, and the project was dropped by the Army.

Under the name [[Project Diana]], the Evans staff took up the possibility of bouncing radar signals off the moon. Calculations showed that standard pulsed radar like the stock SCR-271 would not do the job; higher average power, much wider transmitter pulses, and very narrow receiver bandwidth would be required. They realized that the Armstrong equipment could be modified to accomplish the task.<ref>{{cite book | first=Cindy Stodola | last=Pomerleau | year=2021 | title=To the Moon and Back: Essays on the Life and Times of Project Diana | pages=91–96 | publisher=Amazon Digital Services LLC - KDP Print US | isbn=979-8-706-54632-8 }}</ref><ref>{{cite web | title=Project Diana: Radar Reaches the Moon | url=https://www.projectdiana-eme.com/| accessdate=July 13, 2022}}</ref> The FM modulator of the transmitter was disabled and the transmitter keyed to produce quarter-second CW pulses. The narrow-band (57&nbsp;Hz) receiver, which tracked the transmitter frequency, got an incremental tuning control to compensate for the possible 300&nbsp;Hz Doppler shift on the lunar echoes. They achieved success on January 10, 1946.