Whenever I’m driving out of my usual listening area and trying to find the local NPR (always between 87 and 92 FM) I keep hitting religious stations. Occasionally I’ll come across a commercial station, but usually it’s either NPR or a religious channel in that range.
Is that range specifically reserved for non profit broadcasting? If not, is there a reason that the religious stations and NPR affiliates have such similar frequencies?
We just covered this in my mass-communication class today. In 1945, the FCC set aside 88.1Mhz-91.9Mhz FM for public radio.
There is indeed a “noncommercial” band set aside by the FCC exclusively for nonprofit broadcasting. Since 1945, this FM band has been set at the 88-92 Mhz range (some sources say 88.1 - 91.9). This timeline from the Corporation for Public Broadcasting confirms it. So yes, there is indeed a reason for the presence of both NPR affiliates and religious stations on that FM range.
Interestingly, because of this exclusive bandwidth, there has been a struggle between religious broadcasters and public radio stations over airwave usage. This article from NY Times in 2002 details some of the clashes between American Family Radio and NPR.
Since all FM stations have an odd number in the tenths-of-a-megahertz position, the lowest station in the 88 to 92 range is at 88.1, and the highest is at 91.9.