P operates a Chicago AM radio station on a frequency of 820 kHz, one of the so-called clear channels. 'Clear channel' rules certain AM frequencies are designated as clear channels that can be used at night only by specified stations that broadcast a signal to 'white areas,' sparsely populated regions that have no local radio service. Because of the 'skywave contour' characteristics of nighttime radio signals, other stations broadcasting on a 'clear channel' frequency must close down at night to avoid interference in 'white' area reception with those stations particularly authorized to transmit this special nighttime signal. P operates on a sunrise to sunset basis. P filed an application requesting a waiver of the clear channel rules. P would construct a directionalized antenna that would beam its signal away from 'white' areas that were being served by stations WBAP and WFAA, licensed to operate clear channels. P proposed its equipment would alleviate interference. P touts its distinctive adult audience, able during the evening hours to listen to, and understand serious social, political, and educational programs, and it claims that the limitation on its channel is a limitation on communication of ideas. D said no. P appealed.