But if you find an FM receiver from 1940 it won’t work because FM was originally assigned 42 to 50 MHz and was moved to its current frequencies, obsoleting all the transmitters and receivers, in 1945.
The was because David Sarnoff used his political influence to move the FM band in order to bankrupt Edwin Armstrong. Armstrong had a company and was producing FM receivers. RCA wanted to horn in on the action. Armstrong started out at RCA and his invention and patenting of the superheterodyne receiver gave RCA a virtual 19 year monopoly. He never got along with David Sarnoff.
Upon hearing of Armstrong’s apparent suicide, the very first thing Sarnoff said is reported to have been, “I did not kill Ed Armstrong.”