For decades, people large and small have looked at their televisions and asked a simple question: What happened to channel 1? It’s a question I answered in a different article. Channel 1 was reallocated to other uses in order to stop conflicts. But most people aren’t aware that for decades, there was another “missing channel” and its story is just as interesting… if not more.
When did channel 37 start to be a thing?
Channel 37 was first allocated in 1952 when UHF broadcasting was opened up. Before that, only channels 2-13 were available. Because broadcasting was such an inexact science in those days, no city could have two channels on adjacent frequencies without interference. This meant that even though there were 12 available frequencies, the maximum number of channels was about 7, sometimes fewer. This wasn’t going to be enough for the growing television industry.
Originally, UHF channels spanned from 14 to 83. The government thought at that time that would be enough. And it was. Over time, that pool of frequencies was shrunk. First, they took away 70-83, then 51-69. In the most recent channel reallocation, channels 38-51 were also removed.
Digital broadcasting is more precise, so those “adjacent channel” rules weren’t needed. The addition of subchannels meant that you could have more program sources on fewer frequencies. Plus, with cable and streaming, there wasn’t the same demand for traditional broadcasting.
One thing that most folks never realized, though, is that channel 37 had been gone for a long time. How it disappeared, and why it disappeared, is an interesting story.
Channel 37 and the mysteries of the universe
While television broadcasting was growing here on land, scientists were also using the same technologies to search the universe in new and unique ways. One of those was the growing field of radio astronomy. Radio astronomy uses radio waves to map the universe in the same way visible light has been used for hundreds of years. it can tell us a lot more about distant regions of space than we can see with the naked eye.
At the time radio astronomy was starting to take off, the limitations of the day kept most radio astronomy equipment to three sets of frequencies. 410MHz, 610MHz, and 1,400MHz were all key to the early days of radio astronomy. Those three frequencies had two features that made them attractive. First, when combined, they allowed for a very full picture of the sky. Think about how red, green, and blue combine to give you a fuller picture of the visible world around you. That’s similar to the way those frequencies are used.
Second, these frequencies made sense, given the manufacturing limitations of the day. Equipment using those frequencies was easier to build and maintain, and those frequencies were easier to detect through the atmosphere.
The problem: television stations and 1950s technology
There weren’t very many TV broadcasters that really needed channel 37, but there were a few. As I said, you really needed to keep TV broadcasts spaced far from each others. This was hard enough with VHF, but with UHF there were additional issues. In addition to making sure you avoided adjacent frequencies, you also needed to avoid harmonics. Harmonic frequencies are those that are a perfect power of two different from the original. In other words, if you wanted to broadcast on 610MHz you also had to worry about someone broadcasting on 305MHz and 1220MHz.
Those stringent rules meant that for one station in Paterson, New Jersey, 37 was pretty much the only choice. And while this station was far far away from Illinois where there was a radio telescope using that frequency, astronomers worried.
The solution: no one gets channel 37 (except scientists)
The struggle for channel 37 was surprisingly high-profile considering it was about fairly obscure science. In the end, the FCC did the right thing and put in a 10-year moratorium on broadcasting on channel 37. It got extended over and over until it was finally made permanent.
In the meantime. TV makers did their best to keep you from realizing there wasn’t a channel 37. You could still tune to it on any television, but there never was anything there. Eventually people forgot about the controversy and the world moved on.
Channel allocations today
Today, television broadcasting uses channels 2-36, which is more than enough. There are no adjacent channel rules anymore, because digital broadcasts don’t need them. And, astronomers happily use channel 37. They’ve even learned to share it with some very low-powered medical equipment.