Visualizing the Geography of FM Radio

This project, like the one before it, started as an offshoot of another project that I’ll finish… someday…

I start one project, which brings up questions I need to answer in other projects, so I start those projects, which lead to more questions… and before I know it I have a tangled mess that’ll take months to sort out.  To illustrate, there’s currently 11 projects in my “Active” queue and 11 more in my “Paused” queue. I’m personally very proud that I get anything done at all!

For this particular tangled project mess, I needed to see how many classical music radio stations there are in the States. That quickly lead to wanting to plot where those classical stations broadcast. That lead to a burning desire to map all radio station broadcast areas, ever, and also to map how many radio stations broadcast in a given area.

Getting the Data

Amazingly, I was able to satisfy these admittedly strange desires fairly easily.

The FCC provides service contours for more than 20,000 FM radio stations. A service contour is the area in which the radio station may be received without interference from other stations broadcasting on the same frequency. Radio stations can usually be received at much further distances than the service contours indicate, but the FCC doesn’t provide data on the limits of station reception.

I took these service contours and joined them to a list of licensed stations to hopefully filter out defunct or otherwise irrelevant stations. To be honest, I’m not sure I totally understand the results on this list, as there do seem to be duplicate stations with the same service contours. In the absence of any more information or guidance, I took the data on good faith and used it as it came.

Finally, I was able to identify the broadcasting formats (e.g. Top 40, Adult Contemporary) for about half the stations on my list thanks to

Mapping FM Radio service contours

I started by simply plotting the service contours of the 20,000-odd stations on my list. I love the way this looks, like phosphorescent jellyfish or raindrops on water.


I also mapped the service contours of stations with particular formats:


Next, I calculated the number of stations available at any given point:


Unexpectedly, at least to me, the Salt Lake City area beats the rest of the country by a long shot. Some areas of SLC can receive over 60 stations without interference from other stations on the same channel! By comparison, the SF Bay Area is a distant second with 50-odd stations available.

I’m honestly not sure if this is a flaw in the data or the reality on the ground. A manual review didn’t turn up any suspiciously duplicated information or anything else that looked off. Anyone know of any reason why the state might be so radio-obsessed?

I loved this map because it looks like drops of ink spreading in water. The effect is more pronounced when looking at individual states or cities:



TV Stations

The FCC provides the same service contour data for broadcast TV, so of course I had to make maps for that as well.


I would love to know what those horizontal chains of TV stations in the Midwest are! Google has completely failed me in finding out.


Again, Utah sticks out. There’s tons of tiny TV stations scattered across the state in a way I don’t see anywhere else. It also appears the area around Cedar City receives more than 100 stations–more than SoCal or NYC! As with the radio stations, I don’t know if this is an issue with the data or the reality on the ground. I’d really like to find out what exactly is going on, as it’s unlike anything else in the country.

The “ink in water” appearance is even more pronounced on these than the radio station one, in my opinion.



In conclusion

This was a lovely exercise in mapping a bit differently than what I’ve seen out there. I took this in a more artistic than informational direction (admittedly the lack of AK and HI on the maps was due to my aesthetic preferences), but I do think there’s insights to be had from the maps.

One insight that has eluded me, though, is why Utah is so darn strange when it comes to broadcasting. It has many more radio and TV stations than other states, and they’re distributed weirdly, too. Maybe a Utahan could opine?

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