Why do certain types of radio stations cluster in the same parts of the FM spectrum?

January 14, 2011 3:45 PM

Why do certain types of radio stations cluster in the same parts of the FM spectrum?

Is it my imagination, or do NPR/public radio stations tend to be in the high 80s or low 90s, near the college and Christian rock stations, no matter where I am in the US?

There always seems to be a "Hot-100" top-40-crap station around 100 MHz, too.

Overall, it seems like the 92-104 MHz range is the prime radio real estate, with the upper and lower VHF fringes less so, based on the types of stations. Is that true?

posted by gottabefunky to media & arts (9 answers total)

The FCC grants licenses to Non-Commercial Entertainment stations in the 88.1 - 91.9 FM band.
posted by Burhanistan at 3:53 PM on January 14, 2011 [4 favorites]

Burhanistan shows why the preferred ranges starts at 92.0.

Not sure, but I'm guessing that some analog-tuning radios may not tune all the way to the top of the spectrum (their top freq is often based on how far the mfgr sets the mechanical stops on the tuning coil, which isn't 100% accurate in location from one set to another).

Given that many radio licenses haven't changed hands since the days of physical-dial-tuned radios, I would prefer to invest in a station that is located well below the maximum freq (107.9?). Thus, the upper (soft) limit.
posted by IAmBroom at 5:33 PM on January 14, 2011

In June of 1945, the FCC moved the FM Band to 88 to 108 MHz "with 88-92 MHz reserved for noncommercial broadcasting, and allocated 106-108 MHz for facsimile broadcasting. Within the 92-106 MHz spectrum, FM stations were to be allocated as follows: 92.1-93.9 community; 94.1-103.9 metro; 104.1-105.9 rural."
posted by Rob Rockets at 5:33 PM on January 14, 2011 [2 favorites]

Side note is that they added space to the AM band fairly recently. My 1993 car radio goes up to 1530, my 1997 one goes to 1710, I think. Those stations are going to be newer stations.
posted by gjc at 5:47 PM on January 14, 2011

In some areas you get a lot less crowding around a particular frequency because they've got a strong signal, which over time also affects the real estate - you want to be close because then if someone's dashing off of that channel to skip commercials, you're right there - but you don't want to be too close.

In Columbus, Ohio the major pop/mainstream stations are at 94, 95, 98, and 104. The 100-102 area used to be dominated by alternative, but just got sold to WOSU and is now 24/7 classical music. I believe the most powerful transmitter is at 97.9, which seems to have been why everyone else is right there. 97.1 is sports but was mainstream music for a few decades. The 104s are soft contemporary and religious music.

(which is to say - there's nothing special about 100 except that it's smack in the middle of the "metro" range.)
posted by SMPA at 6:43 PM on January 14, 2011

NPR and religious organizations more than likely use the non-reserved band - which is 88.1 to 91.9 because it is specifically reserved for nonprofit organizations with an educational purpose, educational institutions or government organizations. That said, it is possible for a noncommercial educational station to also be on the commercial band. They have to file an application to do that, though.
posted by Leezie at 7:03 PM on January 14, 2011

Possibly related to the belief that the best place for a gas station is next to another gas station.
posted by StickyCarpet at 7:18 PM on January 14, 2011

As has been pointed out, there is a licensing reason for the non-profits to be where they are. Beyond that, I really think that formats are all over the place and you've got a bit of confirmation bias about where you remember different formats.
posted by randomkeystrike at 8:20 PM on January 14, 2011

Some of it's "location": in the Old Days of physically tuning up-and-down the dial, the stations in the middle of the band would get the most traffic just tuning by; thus the mid-dial is where you want to put your station.

Ergo, Top 40 radio would congregate in the middle of the band, the higher and lower frequencies being less desirable.

And, as has been explained above, all the good stuff is on the Left of the Dial
posted by AsYouKnow Bob at 9:31 PM on January 14, 2011 [1 favorite]