⟩ Explain me what Frequencies Were Used By Early Broadcasters?
☛ AM:
In 1922, all stations were assigned by the Secretary of Commerce to 360 meters (833 kHz) for the transmission of "important news items, entertainment, lectures, sermons, and similar matter."
Later that year, 400 meters (750 kHz) was added, with power limits raised to 1,000 watts. One frequency was set aside for music broadcasts, the other for news and other voice transmissions.
In 1923 and 1924, additional changes were made, opening up 550 to 1500 kHz for broadcasting (in 10 kHz increments) with powers up to 5,000 watts. (The band from 810-850 kHz was "left" for the stations on 833 to continue for a while).
In 1938, an administrative conference designated 1500-1600 kHz to be opened in May, 1941.
In 1979, the WARC expanded the band again, this time to 1700 kHz. The first station on the new band was WJDM, Elizabeth, NJ, which went on in 1995.
☛ FM:
The original FM band was 43.0 to 50.0 MHz, but unlike the present, the assigned channels were on the even frequencies (43.6) instead of the odd (98.3).
The band was originally to be used for experimental "high-frequency AM stations," where the channels would be spaced farther apart (200 kHz) and permitted to broadcast the full frequency spectrum. The idea was to relieve the congestion and skywave problems which would lead to the severe bandwidth limiting which would eventually doom the AM band to talk radio and poor quality radios.
☛ TV:
The original TV band ran from 50 MHz to 108 MHz and was designated channels 1 to 7. In June 1945, as part of his campaign against FM, David Sarnoff had it moved down to 44 MHz.
The low TV channels soon proved to be woefully inadequate for the expressed interest in TV broadcasting, so the FCC decided to go back and allocate more spectrum. They also decided to deal with some of the problems being seen with severe skywave on channel 1. Therefore, in 1948, channel 1 was officially dropped, with channel 2 starting at 54 MHz. (Channel 2 still has the skywave problem - or "benefit," if you are a TV DXer - of the early years, but since FM was moved up to the high-band no broadcast service was affected by the interference from TV.)
