Much of the plot of the movie is about the management of the station resisting the push to change to stations format to include more commercials than music. Tom Petty, who has a cameo in the film, fought his own battle against his recorded label over the album "Hard Promises". The album had been given the superstar price of $9.89, versus $8.98. Petty balked at the change, threatening to hold up the album's release.
Much like the characters in FM, this stand won Petty a loyal fan base standing behind him in support.
The advertisement that was presented by the men in military uniforms was an actual advertisement for the delayed entry program which offered new recruits the opportunity to "grow your hair one more time". It was an attempt to make the Army more hip in light of the changing culture shortly after the Vietnam war.
In the original theatrical release shown in movie theaters, Linda Ronstadt gives a plug to singer/songwriter Karla Bonoff's debut 1977 LP (which Ronstadt sang on) during her concert footage. That scene was cut from the later VHS tape release.
QSKY's FM Frequency is listed in the movie as 108.1. That is impossible in the US as the FCC (1934) set FM's frequency range from 87.8 to 108.0Mhz. That said, all FM broadcast stations end with an odd number beginning with 87.9Mhz and ending in 107.9Mhz, and are all in increments of .2Mhz.
The microphones in the movie in the main booth are stereo AKG C-414 models and the speakers are JBL 4311's. The turntables in the booth are Technics SP-10's. Other hi-fi gear seen are a Marantz receiver and SAE amplifier and EQ.