This one's for the old-school analog television fans.
March 16, 2021 9:03 AM   Subscribe

Why was there no channel 37? It's pretty darn technical, but the upshot is, apparently, aliens.
posted by JanetLand (25 comments total) 21 users marked this as a favorite
 
Wait so 610 MHz was picked for radio astronomy because of accident of engineering?
we decided for engineering reasons that we could only build a really big one if we had a frequency round about 600 megahertz. Otherwise, the perfection of the reflector, if we went to a shorter wavelength, was not something that you could [do] by the acre, at least not at that time
I was thinking it was some fundamental physics thing like 1420MHz, the hydrogen line. Funny that this was just the highest frequency they could build for at the time so it became a standard.

Did anyone live in a UHF market that was near saturated? Growing up in Houston in the 80s I think we had maybe 6 UHF channels broadcasting. But there's some 70 UHF channels allocated, it seems like removing one for science wouldn't have been such a hardship. Maybe they needed a lot of spacing to manage long distance interference.
posted by Nelson at 9:23 AM on March 16, 2021 [3 favorites]


Wait so 610 MHz was picked for radio astronomy because of accident of engineering?

More like the limits of engineering. The radio telescope was basically dug out of a ravine and then they used asphalt and wire mesh to make such a huge reflector. They could only get things to conform so well given the material science and construction methods of the time. Once one gets to higher frequencies it's going to start to scatter off the texture of the parabolic reflector instead of reflect back to the antenna. Nowadays we have large parabolic dishes that are extremely smooth or we have radio arrays using interferometry and digital signal processing to image the sky.
posted by Your Childhood Pet Rock at 9:44 AM on March 16, 2021 [2 favorites]




Was the correspondence between frequencies and channel numbers US/North America-specific or international? In Australia they had a set of (older) VHF channels numbered 0-13, with some oddities (there was a 5A between 5 and 6, for some reason), and UHF channels (mostly containing local repeaters of canonically-VHF stations, though channel 28 (SBS) being an exception) from twentysomething to the 60s. I'm wondering whether the channel numbers were the same as the US ones (not counting the PAL/NTSC difference), or whether places which didn't have formal channel numbers, such as the UK, had them but just didn't refer to them publicly.
posted by acb at 11:06 AM on March 16, 2021 [1 favorite]


The article also mentions that you could get the audio of Channel 6 analog TV at 87.7 MHz, which some radios could tune to. I definitely remember using this to get Jeopardy! in the car, because it's a rare show that actually mostly works as audio.
posted by madcaptenor at 11:10 AM on March 16, 2021 [8 favorites]


In Sputnik-era America, scientific resource preserved from capitalist robbers!
posted by Aardvark Cheeselog at 11:22 AM on March 16, 2021 [5 favorites]


My memory of 60s-childhood TV is that UHF always felt like an afterthought. I suspect this was reflected in the designs of the TV sets of the day on no grounds but guesswork. But probably consumer TVs were always optimized for VHF. Add the fact that UHF is subject to noise sources that VHF isn't to the probable cheaping-out on the UHF receiver and you get something that doesn't work very well.

UHF was sometimes the only option at places way out in the sticks, like grandpa's farm out in northern Iowa. UHF stations always seemed to be lower-budget, despite the fact that the equipment is inherently more expensive and complicated. Around cities, UHF stations seemed to be for niche markets like local sports and Saturday night horror movies.
posted by Aardvark Cheeselog at 11:30 AM on March 16, 2021 [2 favorites]


There's a whole movie about how UHF TV was the backwater with low budget and kooky things on it. Sort of like AM radio (although the history is reversed); less desireable bandwidth is cheaper and allows more experimental TV. Remember back when every big city had a community TV station with some minimal production equipment and free time slots for people to broadcast their own weirdness? Sort of the Youtube of its day, there's a lot of interesting stuff that was broadcast on UHF in only one city. Particularly queer stuff from the 80s in New York.
posted by Nelson at 11:34 AM on March 16, 2021 [7 favorites]


I never lived anywhere which had many UHF channels, but I did have a cheap small portable TV where the tuning dial was a continuous smooth transition (rather than clicks to lock in a channel), which allowed me to eavesdrop on cellular telephone conversations in the mid-90s.
posted by AzraelBrown at 11:43 AM on March 16, 2021


It was relatively hard to build a UHF receiver with good selectivity, so you couldn't assign every channel in a market; they would space the channels 6 channels apart, so you wouldn't get very many before you were "saturated"
posted by Monday, stony Monday at 11:47 AM on March 16, 2021 [5 favorites]


The article also mentions that you could get the audio of Channel 6 analog TV at 87.7 MHz, which some radios could tune to. I definitely remember using this to get Jeopardy! in the car, because it's a rare show that actually mostly works as audio.

Our local channel 6 actually advertised this fact, telling listeners they could listen to the local news and other programming in their car. Unfortunately Jeopardy was (and still is) on a different channel in Augusta GA. Definitely one of the little things I miss about analog TV.
posted by TedW at 11:55 AM on March 16, 2021 [1 favorite]


Related (and also pretty technical) Whatever Happened To Channel 1?
posted by TedW at 12:13 PM on March 16, 2021 [6 favorites]


UHF for me was Lucha Libre on Canal 47, Patterson, New Jersey,
posted by Splunge at 1:01 PM on March 16, 2021


The article also mentions that you could get the audio of Channel 6 analog TV at 87.7 MHz, which some radios could tune to

These stations, known as "FrankenFM" stations, are almost done. The FCC has reminded broadcasters they all need to be turned off by July 13th, marking the true end of analog television in the USA.
posted by JoeZydeco at 1:26 PM on March 16, 2021 [5 favorites]


I had no idea that something that cool existed in Danville, a place that I usually just drive by on my way to Indianapolis for Gen Con. Too bad it's not still there!
posted by Halloween Jack at 1:57 PM on March 16, 2021


To give an idea of how tricky making a UHF tuner was in the late 50s and early 60s: Philips TV Tuner History pt2: UHF
posted by Monday, stony Monday at 2:00 PM on March 16, 2021 [2 favorites]


Ironically, it's VHF that has become undesirable for digital TV because the type of interference found in the lower part of the band (between channels 2 and 5), does a number on a lot of ATSC tuners, especially the early ones.

I remain annoyed that the TV allocation keeps shrinking in the US just so that cell phones can have more and get worse as a result. It was hard enough to build good quad band radios and now they basically have to have 6-8 different frequency bands. Heaven forbid that the cell carriers actually make efficient use of their allocated space in the manner intended, by subdividing cells. It's called cellular for a reason. It would be less annoying if the extra space were going to new competitors and if it wasn't impacting the quality of DTV broadcasts due to packing more and more subchannels into the fixed bandwidth available to each physical transmitter.

The channel numbering isn't global, by the way. The spacing is different between the various standards. A channel in North America is 6MHz wide. In Europe, Australia, and other PAL/DVB-T countries it's bigger. I think 8MHz, but I could be misremembering the exact number.

Also somewhat interesting is how the band plan for cable TV (at least in the US) was identical to OTA broadcasts for channels 2-13, but is wildly different for UHF. It made the systems a lot easier to build back when amplifiers were a lot crappier than they are now, but kicked off the whole converter box thing (at least before "cable ready" TVs became a thing). One side effect was that several of the channels numbered in the 90s were actually VHF, stuck between channels 5 and 6 where FM radio, air band, and some other stuff lives over the air.

Also kinda weird is that thanks to the frequencies being different, a lot of cable companies used letters instead of numbers for the channels above 13 early on to avoid confusion. Some even got up into double letters.
posted by wierdo at 3:40 PM on March 16, 2021 [2 favorites]


"Did anyone live in a UHF market that was near saturated? "

Chicago's UHF market was pretty saturated in the 80s, to the point that almost every number on the UHF dial tuned in SOMETHING in the Chicago suburbs, and sometimes the "local" UHF channels would keep flashing in between the strong local broadcast and a weak regional broadcast. Flat terrain makes powerful UHF signals.

There was one UHF station that was out of Kenosha or somewhere, and it would come in on our TV but ONLY if someone stood with their hand on top of the TV and acted as a human antenna. They carried some obscure sports stuff, and my dad used to make whichever unlucky child wandered into the room stand there and be the antenna so he could watch SOCCER or TRACK AND FIELD NATIONALS or other random shit like that.
posted by Eyebrows McGee at 5:53 PM on March 16, 2021 [8 favorites]


Growing up in central PA, we had 3,6,10, and 47. 47 was religious. Later We then got 8 and 23, so it was almost all VHF back then. Now on some days and when we had the big up on a pole antenna we could get from Pittsburgh, 2,4,11. We didn't have an ABC ( that was 23 later ) for most of my childhood, though we could sometimes get Monday Night football via 4 in Pittsburgh.
posted by 922257033c4a0f3cecdbd819a46d626999d1af4a at 6:12 PM on March 16, 2021


UHF TV was the backwater with low budget and kooky things on it

An element in the origin story of MST3K, for example, which started on Minneapolis channel 23.
posted by gimonca at 6:46 PM on March 16, 2021 [4 favorites]


…for niche markets like local sports and Saturday night horror movies.

I was always up to cross the state and visit my grandmother because it meant I'd get the chance to tune into Tampa's channel 44 for the Saturday afternoon Creature Feature double billing of crappy/fun old 50s horror movies.
posted by los pantalones del muerte at 7:13 PM on March 16, 2021 [1 favorite]


37 channels? In a row?
posted by longtime_lurker at 10:40 AM on March 17, 2021 [4 favorites]


There was one UHF station that was out of Kenosha or somewhere, and it would come in on our TV but ONLY if someone stood with their hand on top of the TV and acted as a human antenna. They carried some obscure sports stuff, and my dad used to make whichever unlucky child wandered into the room stand there and be the antenna so he could watch SOCCER or TRACK AND FIELD NATIONALS or other random shit like that.

Someone needs to dig into this story of the obscure-sports broadcast station! I wonder if there were more eccentric non-cable stations, and maybe they had national conventions of independent TV broadcasters, and maybe if I go to a Kenosha Goodwill store I might find a t-shirt.
posted by rhizome at 11:40 AM on March 17, 2021


I wonder if there were more eccentric non-cable stations...

Nevermind!
posted by rhizome at 11:56 AM on March 17, 2021


Fascinating Despite being currently engaged in putting off writing course material on closely related things, I'd never heard this story before. Neat!

I'm not sure that 610 MHz is specifically important. 410 is historical and not actually motivated by any specific features in the sky. (I'm happy to learn I'm wrong.) 1420 has an incredibly unique and important line, but it doesn't have anything to do with lower frequency observations except that you can also measure the continuum in the reserved band where there aren't 21-cm line features. 610 is more or less arbitrary and defined by dish manufacturing constraints. You'd probably want something a bit higher if you could choose anything and wanted a third reserved band. But, having a few broad bands in the few hundred MHz range is a very good thing. 610 is as good as anything else.
As space and astronomy writer Bob King of Universe Today put it in 2013: “Without it, radio astronomers would lose a key window in an otherwise continuous radio view of the sky. Imagine a 3-panel bay window with the middle pane painted black. Who wants THAT?”
That analogy actually seems to work against keeping the band free from interference. If we were talking about three glass windows looking out at the same garden, then astronomers would be fine with just one window. That the windows show different things is key. Maybe using "window" here is a bad choice, despite the common usage when talking about spectrum.
posted by eotvos at 3:18 PM on March 17, 2021 [1 favorite]


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