At the start of the 1920s, radio was a costly novelty for a few thousand amateur ham radio operators. Within four years there were 2,000,000 sets nationwide. The number of radio stations had grown to 530 with little or no regulation of the airwaves, causing extreme confusion, interference, and jangled nerves.
Secretary Hoover chaired a series of conferences that limited radio licenses initially to three months. They designated certain bands to be set aside for public service broadcasting, and decided against British-style regimentation of the airwaves.
Hoover received an angry telegram from radio preacher Aimee Semple McPherson. "Please order your minions of Satan to leave my station alone," it commanded. "You cannot expect the Almighty to abide by your wavelength nonsense. When I offer my prayers to Him, I must fit in with His wave reception." (McPherson eventually eloped with the Commerce Department representative dispatched to explain the realities of federal regulation.)
Another religious sect asked Hoover for permission to build a station from which to disseminate warnings of the end of the world. He told them to spend their money for airtime on existing outlets – if the world was really going to end in a month, it would be a far wiser investment.