It's one of those things that you're always vaguely aware of, but never quite grok...

October 18, 2012 1:29 PM

Explain broadcast television in Canada and the US to me like I'm five.

I've tried to do some basic research on this, but the Wikipedia articles and other resources all assume a starting level of knowledge that I seem to lack, so I thought I'd turn to the hive mind.

The full extent of my current and very limited understanding:
1. TV signals get sent out over the air by local stations.
2. You can pick up more or less channels via antenna depending on where you live.
3. If you want more channels you have to pay for cable or satellite.
4. Networks create the TV programming and then partner with local stations to distribute it.

Things that I am confused on:

1. Affiliate stations. In my current understanding, these are local TV stations that actually send out the signals. In the US, the call sign for affiliate stations seem to apply to both radio and TV - there might be a radio station for WUNC that carries programming from NPR, but then there's also a TV station for WUNC that carries PBS. Affiliate stations pay a subscription fee to the network whose programming they carry, and then send out the signals locally. They make their revenue from advertising, which is a mix of local ads and national ads from the network. Is this more or less correct?

1a. Does one affiliate station generally restrict itself to one major network, or do they carry multiple networks? How likely is it that you can pick up the same network from two different affiliate stations in a particular area?

1b. Is this call sign system also in place in Canada? I've only ever heard of CFRA radio, for example, and you wouldn't watch a TV show on CFRA. (Or would you?) If the call sign system in Canada does only apply to radio, does it only apply to AM radio or also FM? is there a similar naming system for local TV stations?

1c. Americans seem much more aware of the call signs of their local stations than Canadians do, and to them the station (WBEZ) seems to matter as much as the network (NPR). Why is that?

1d. Affiliate TV stations that carry network X get the same programming for network X at the same time everywhere, and only differ in advertising, right? But the same doesn't apply to radio, because I feel like I've heard Car Talk at different times on the weekend. Am I imagining this? Why the differential? Does it have to do with the purpose of radio being primarily information dissemination, and TV primarily being entertainment?

2. Over the air channels. Cable channels go up in nice numerical sequences. OTA channels (both in Canada and the US?) seem to follow bizarre and arbitrary numbering systems. For example, I get channels 7.1, 7.2, 9.1, and then it jumps up to 25.1. Or something. What is the rationale behind the numbering system? What determines which station gets which channel number? Is there any geographic consistency to this? I.e. if PBS is carried by a station that is 25.1 in North Carolina, is it also likely to be carried by a station that is 25.X on the west coast?

3. What determines what network programming you can get OTA? E.g. In Canada you might get CityTV and CTV and all that stuff OTA without cable (and it would go under one of the funny channel numbers like 6-4), but if you want YTV you pretty much have to get cable. What's preventing OTA channels like CityTV and CTV from moving to cable-exclusive broadcasting so they can get subscription fees? Is it the advertising revenue from increased viewership from people who don't pay for TV? And if it is advertising revenue from increased viewership, why aren't all channels (barring, like, HBO) available OTA to get the maximum possible viewership?

3a. In the US it seems to be possible to pick up channels like the CW over the air, whereas in Canada it would definitely be part of a cable package no matter where you lived. Is this because content production happens in the US, and so they have more negotiating power when they go to Canadian stations since Canadian stations want them so badly?

I think that's everything I can think of, but I will follow up if I think of more. Please take me to school, AskMe. Andpleasedon'tlaughathowlittleIknow.

posted by Phire to technology (27 answers total)

1) Affiliates are generally either owned directly by the large networks, or exclusively contract with them. I've never seen a channel carry both CBS and NBC, for example, and the closest I can remember was back in the 80s / early 90s when some channels would carry both Fox and WB or WB and UPN content.

2) When the US switched to digital a couple years ago, stations were given the option of splitting one analog channel (say, 7) into multiple digital channels (7.1, 7.2, 7.3, 7.4). Most stations picked this option because it allows them to run much more programming, and therefore advertising.

3) Geography and profitability, mostly. If you're out in the sticks you might only get your local CBS/NBC/ABC/FOX stations, but here in Chicago I get ~30 or so local stations, each of which runs multiple channels. On top of the usual ones, I get multiple PBS stations, multiple MyTV channels, and extensive foreign language (Spanish, Chinese, Korean, and uh, BBC) channels.
posted by Oktober at 1:39 PM on October 18, 2012

1c. Local news is usually branded with the station's call sign, which accounts for the name recognition.

2. The electromagnetic frequency band that TV broadcasts over is divided up into channels, to keep signals from stepping on each other. If your TV jumps from 7 to 25, it's because nothing is broadcasting on the intervening frequencies. There is no consistency between regions regarding which channels carry which network, except that the networks with more money tend to be lower on the dial.
posted by zjacreman at 1:48 PM on October 18, 2012 [1 favorite]

First off, it's important to point out a difference between public and private broadcasting. The Car Talk example only applies to TV stations that are, like the radio stations that air Car Talk, public stations. Local public TV stations can and do syndicate content and air it wherever it fits their schedule.

Secondly, radio and TV stations do not share call signs. WUNC is a public radio station. UNC-TV is a public TV station.

Also, those public TV and radio stations do not make revenue from advertising. They are funded mainly by listeners.

As for call sign recognition, your example is, again, a public radio station. All of those stations are local, and they do not, as noted above, have a rigid, unified schedule nationwide. They each get programming from different sources (Public Radio International and National Public Radio are the main ones) and most also produce their own local content. So no one is listening to a generic feed from "NPR." They're listening to a local station with content from NPR, and also PRI etc.
posted by ronofthedead at 1:54 PM on October 18, 2012

I don't have a lot to add, but you should be aware that Public Broadcasting is a pretty different beast than commercial. Frequently different public radio stations will air the same show at a different time slot. This happens with syndicated shows on commercial tv (and maybe radio?), but I can't think of an example of a first run show being aired multiple times on competing commercial channels.


More or less what ronofthedead said.
posted by mzurer at 1:56 PM on October 18, 2012

Affiliate TV stations that carry network X get the same programming for network X at the same time everywhere, and only differ in advertising, right? But the same doesn't apply to radio, because I feel like I've heard Car Talk at different times on the weekend. Am I imagining this? Why the differential? Does it have to do with the purpose of radio being primarily information dissemination, and TV primarily being entertainment?

I work for a nationally broadcast TV show:

Television network affiliates are generally under contract to air programs from their network at a given time, but there are exceptions. For instance, your local station may opt to time-shift primetime programming to show a local team's game if there's a conflict and a chance at better ratings. Affiliates in more conservative areas may refuse to air a show that they believe will run afoul of community standards.

I believe that PBS is even looser than American commercial TV-- some affiliates run programs an hour off from the official primetime schedule. For instance, PBS moved FRONTLINE to an "official" ten PM start time, but a large percentage of PBS affiliates were already airing it at ten.

Also, there's a distinction that needs to be made between Network programming and syndicated content. The networks typically provide evening and morning programming and stipulate when it airs. The rest of the content is locally produced, or sold to the affiliate by a third party syndicate to fill in the rest of the time. Syndicated content could be new sitcoms, dramas sci-fi or game shows. It could also be reruns of old shows. No one tells your local station when it can air reruns of "Mama's Family," providing that they're not using it to replace national programming.

Radio stations are almost all syndicated content. Talk radio shows are generally syndicated and it's up to the station to find the appropriate place to fill it. Likewise, NPR affiliates aren't under tight obligations to air specific content at a specific time. It's just an operational difference because there doesn't tend to be a national producer of content. Even most shows on NPR are made by member stations and not by the parent.
posted by Mayor Curley at 1:56 PM on October 18, 2012 [1 favorite]

1a- In the US, affiliates are exclusive to one network. It wouldn't be possible to show prime-time sitcoms and dramas from two networks simultaneously, and the networks wouldn't take kindly to time-shifting in order to appease their competition.

1c- Most local channels also offer local news, sports, and other programming. People have preferences for the news team or weather person or sports person they like best, hence they have a greater knowledge of the channel and thus the call sign.

2. Channel numbers are a representation of the frequency the station broadcasts on. It's easier to remember "channel 3" than 743MHz. Stations will broadcast on different channels in each region based primarily on lack of interference in that frequency band as well as other factors. There isn't, at least in the US, any consistency (other than by chance) of a network being on the same channel in multiple markets.

3. Broadcast networks (and their local affiliates) already receive "retransmission" fees from cable and satellite providers, who carry those stations to their subscribers within that geographic region. So going cable-only would actually decrease their viewer base by only cutting out the antenna-only households.

But - OTA networks require a large network of affiliates. It used to be that most markets had a handful of independent stations. But these were eventually bought out or contracted to networks like Fox (early 80s), UPN and WB (early 90s; now merged into CW), and MyTV (2000s). The remaining independent stations are only in certain markets, so it's essentially too big a hurdle for a new national broadcast network to open up shop in the US.
posted by trivia genius at 1:59 PM on October 18, 2012

Ack. I just realized that SOME radio and TV stations do share call signs. The one that comes to mind is WGN in Chicago. I believe that's mostly leftover from a bygone era of call sign regulation, but I'm not 100 percent sure.
posted by ronofthedead at 2:00 PM on October 18, 2012

ronofthedead: "First off, it's important to point out a difference between public and private broadcasting. The Car Talk example only applies to TV stations that are, like the radio stations that air Car Talk, public stations. Local public TV stations can and do syndicate content and air it wherever it fits their schedule. "

So do commercial radio networks get to stipulate when their programs are aired on an affiliate station, the way commercial TV does?
posted by Phire at 2:01 PM on October 18, 2012

Also: all my examples are public broadcast examples because that's the only thing I listen to outside of podcasts, heh.

Thanks for all the detailed and thoughtful answers so far, everyone, this is super helpful.
posted by Phire at 2:04 PM on October 18, 2012

Actualky, the only American channel I get OTA in my part of Toronto is The CW affiliate in Buffalo or Rochester (not in the summer, though, because I'm in a bit of a valley in the middle of some hilly ground in the west end.)

I'd rather have PBS, but that only came in one brief, glorious Sunday when I moved the tv to the kitchen and put the antenna up where it scratched the paint on my ceiling. Monday: nothing.

OTA is a fickle goddess.
posted by maudlin at 2:09 PM on October 18, 2012

2. OTA channel numbers are a vestige of the UHF/VHF broadcasting system in the US.
posted by Rock Steady at 2:13 PM on October 18, 2012 [1 favorite]

As Mayor Curley said above, commercial radio stations are mostly a mix of locally produced and syndicated content. There's really not a national commercial radio network, per se, that has local affiliates the way network television does.

However, a lot of that syndicated content is live, and it is aired at the same time everywhere. That goes, especially, for live call in shows like a lot of national sports shows and talk radio programming like Rush Limbaugh, although a few stations can and do air these shows on tape delay, for whatever reason.

Programming on any radio or TV station is dependent on several factors. Public or commercial, as mentioned. On radio, there are broad formats like "talk radio," or "sports radio," or "music radio" that affect what gets aired when. A talk radio station and a music radio station might both get their news content from a shared syndicated source but have nothing else at all in common programming-wise.

Also, there are local TV stations that broadcast over-the-air that are commercial but are NOT affiliated with one of the national networks. There used to be a lot more of those before the giant media conglomeration that's gone on.
posted by ronofthedead at 2:19 PM on October 18, 2012

When a radio station brands itself as being a network affiliate, it almost always does so based on its news network and only its news network; "NPR News networks" are all public radio stations, natch, but that doesn't mean they exclusively air NPR content. They may air their own content (classical music, often, or jazz, or local talk shows) or air content from other radio sources such as PRI (Public Radio Int'l) or APM (American Public Media, which is in some form the remnant of what was once Minnesota Public Radio, which was itself a union of all the public radio stations in that state.

Plenty of all-talk radio stations get news from a major provider like Reuters or CBS News, and so they'll be "your CBS news station."

On the topic of TV station ownership, it's true that each of the major networks owns and operates many stations, so these stations are called, e.g. Fox O&O's for "Owned and Operated."

Other stations are owned by newspapers or smaller corporate networks-- Fisher, Tribune, Hearst, Journal, many others. These companies (like the big guys) can't own more than one station in the same market (e.g. town) but they also aren't exclusive to a network-- their stations are. So Fisher can own an ABC, 3 NBCs, 2 CBSes (I made up the numbers, but Fisher Broadcasting is a real network).
posted by Sunburnt at 2:25 PM on October 18, 2012

1b. Is this call sign system also in place in Canada? I've only ever heard of CFRA radio, for example, and you wouldn't watch a TV show on CFRA. (Or would you?) If the call sign system in Canada does only apply to radio, does it only apply to AM radio or also FM? is there a similar naming system for local TV stations?

The call sign system works pretty much the same in Canada. Most (if not all) Canadian stations have callsigns starting with C. In the U.S., of course, it's divided in two: callsigns west of the Mississippi usually start with K, and east of the Mississippi they usually start with W.

In my recollection, most broadcast stations in Canada tend to brand themselves using a name other than their callsign (i.e., they call themselves "CityTV" even though their callsign is CHMI.) Some stations do use their callsigns in their branding, though; people did "watch shows on CKND" when I was growing up in Winnipeg.
posted by Johnny Assay at 4:24 PM on October 18, 2012

So do commercial radio networks get to stipulate when their programs are aired on an affiliate station, the way commercial TV does?

To some extent; yes. Really, the main factor is clout. Shows like Limbaugh don't allow stations to time shift. If you take Limbaugh, you have to take it live. There are other shows for which this is not the case - stations will use them as filler during the overnight, or on the weekends.

The other aspect that can't be overlooked is that a lot of the carriage contracts between provider and broadcaster are hammered out on an individual basis; aspects like cost and broadcast time can vary wildly between stations.

Also, there is at least one public radio program that can't be timeshifted - Prairie Home Companion has to be played live. Stations can then rebroadcast it whenever they want (and many do), but the original broadcast has to be during the initial feed, Saturdays at 6pm est.


As far as what stations carry, radio is a different animal than TV. In public radio, for example, there are a lot of difference sources for programming. A station can get programs from any of the following networks: NPR, the BBC, the CBC, PRI, APM, PRX, or Pacifica. They can also source programming from statewide consortia, like Virginia Public Radio, or Wisconsin Public Radio. They can get programs from independent producers, or they can form agreements to carry programs produced by other stations. And of course, they can produce their own shows.

This leads to a lot of confusion about what pubic radio is, and stations work both sides of that angle - when it's convenient to be associated with NPR (high quality reporting! great programs!) they do that, and then when it's not convenient (Ron Schiller, Juan Williams), they can back off and say, "That's not us, that's the network!"
posted by god hates math at 4:58 PM on October 18, 2012

2. OTA channel numbers are a vestige of the UHF/VHF broadcasting system in the US.

Digital TV is still broadcast (broadcasted?) on the same VHF and UHF frequencies that have been in use for decades. The difference with digital channel numbers and analog channels is that there is a layer of abstraction between the two now. The problem stems from the fact that television stations have a lot of history and recognizability in their markets based on their channel numbers, rather than their callsigns or network affiliations. So the television stations wanted to retain those channel numbers.

However, in doing the transition from analog to digital, the frequencies that the stations' programming was getting broadcasted on had to be changed in a lot of cases. Partially because for about 5 years, stations were broadcasting their programming on both digital and analog, and you can't broadcast two things on the same frequencies at once. So, the digital broadcasting standard was changed to allow the signal to tell the television what channel it wanted to be displayed as. So the TV can receive a signal on any channel, and that channel will say "hey, even though I'm coming in on channel 47, you should display me as channel 2".

The other thing that digital did was made the signal more uniform and less noisy. If you look at this, on the left is a digital signal. A nice uniform blob. On the right is analog, which is spikier. It needed to go "louder" (higher peaks, more wattage to the transmitter) in order for the lower peaks to be loud enough to be heard.

A real world example is FM radio. If you are far from a station, you'll hear it go in and out of stereo, or you may not be able to hear stereo at all. This is because, like the analog TV signal, it has multiple components. A tall, loud mono signal, and then a more quiet stereo signal.

Anyway, a side effect of this is that for a signal to be powerful enough to be heard over the geographic area, it has to be broadcasted with more power. This creates noise on that frequency over a much larger area. You can't get Chicago stations in Milwaukee, but there is enough noise on those frequencies that they can't be used for anything there.

With digital, the stations don't need as powerful of a signal to cover the same area, so they were able to reduce the number of available frequency slots throughout the country and just distribute the different stations more closely together.

So by adding that layer of channel numbering (virtual channels), television stations could retain their traditional numbers while at the same time being broadcast on whatever channel worked. This also had the effect of making more licenses available for low power broadcasters.

(As for numbers corresponding to networks, I think CBS tried to be on 2 where it could, and ABC tried to be on 7.)
posted by gjc at 5:28 PM on October 18, 2012

1. Mostly correct. In the past networks paid the stations to take their programs, and kept the ad revenue from network commercials. Affiliated stations would usually get two to four minutes of time per hour that they could sell to local sponsors. Now that has turned around -- stations are now paying networks for their content, while still getting the local avails.

1a. Back before digital let stations broadcast more than one program at one time, smaller cities that had only two stations usually had one that was full-time with one network and one that split the other two. For example, when I visited my grandparents in central Texas, Abilene's channel 9 was NBC and channel 12 split CBS and ABC, usually showing whichever network was more popular. Waco was similar, with channel 6 carrying NBC and some ABC shows, and channel 10 carrying CBS and some ABC shows. My grandparents got the Abilene, Waco and Dallas stations. Just depends on how tall an antenna you put up.

Now with digital TV and more stations on the air, there are many many fewer dual-affiliate stations. Channel 12 in Beaumont, Texas runs ABC on 12.1 and NBC on 12.2.

1b. The call sign system is in place around the world, but most countries don't require each transmitter to identify itself. Last I remember, Canadian stations are required to broadcast their call signs three times a day. Other times they'll just identify with their branding ("Fox 26" here in Houston is KRIV, and you'll only see that on their legal ID graphic once an hour).

1c. Canadian TV has evolved from an affiliate system (CTV was originally a cooperative owned by all its affiliates) to one where the network owns all the stations (except in the smallest towns -- Lloydminster and St. John's are two examples). "CTV Toronto" used to primarily identify itself by its call sign, CFTO. CBC and Global are the same. The "Citytv" system grew from one station in Toronto with the call sign CITY-TV.

ronofthedead: Once upon a time the same call sign could only be used by commonly owned AM, FM and TV stations in the same city. That has been considerably loosened -- KPRC-TV and KPRC (AM) in Houston were once commonly owned, but no longer are.

gjc: ABC applied for channel 7 in the cities it wanted because at the time they thought channel 7 would be the upper end of the TV dial.
posted by Gridlock Joe at 5:39 PM on October 18, 2012

Callsigns: the importance of callsigns is different in the US between radio and TV. They basically don't matter for broadcast television. The channel number is the thing. Whereas in radio, the callsign is much more important. Partially because radio can be consumed without looking at the radio. How will a passerby know what station they can find this awesome music or Lone Ranger program? By the announcer saying "WBBM, AM 780". You have a name and a number to remember together.

Also, with PBS, there isn't really a hierarchical structure like there is for the other networks. The "big" stations create their few signature shows, and then the other stations simulcast them. It's more of a mesh network. I don't think PBS produces (very much) content that doesn't originate at one of the stations as a local show.

As for cable versus over the air and why don't they change, it is partially because broadcast TV is expensive. They have to foot the bill of creating the content and distributing it via just the advertising. (Versus subscription-only cable, which does it strictly through fees.) Cable stations are generally pretty cheap to run, because viewers LIKE the fact that they can see reruns all the time. Especially back in the non DVR world. So they only really had to purchase a few hours of new content every week, and then run it over and over with inexpensive advertising.

There was also the issue that there was not a good way to do ratings for cable. They sold advertising based on how many homes the signal got piped into. That has changed now, but the effects are still there.

Mostly though it's just because that's the way it's always been done.
posted by gjc at 5:43 PM on October 18, 2012

Canadian here.

1b. The call sign system does apply to Canada. People who work at broadcasters would look at it all the time (when they're looking at audiences, selling ads, etc.). But yeah, generally people either refer to whichever of the big broadcasters they're watching (City, CTV, Global, or CBC) or the "specialty"/subscription channel which is not part of a network. A lot of the differences between the Canadian and American industries reflect the fact that the Canadian population is way tinier - audiences in Canada (and therefore advertising revenue) are just way smaller. There aren't nearly as many stations.

3. What's preventing OTA channels like CityTV and CTV from moving to cable-exclusive broadcasting so they can get subscription fees? Is it the advertising revenue from increased viewership from people who don't pay for TV?
The amount of people in Canada who don't pay for TV in some form or another (cable/satellite) is relatively minuscule, although they are concentrated in politically important areas (Toronto and Quebec). Do you remember the big fee for carriage debate that went on a couple years ago? Although if you're not a TV watcher you probably don't. That whole argument was about the broadcasters wanting a slice of the subscription revenues of cable/satellite providers (since the argument was those providers were earning subscription dollars at least in part by offering the big broadcasters' channels to their subscribers.... this becomes a bit of a moot point as the cable/satellite providers have since tended to buy up the broadcasters).

The CBC is a different story. It's paid for, mostly, by taxpayers (and its existence is a matter of law as per the Broadcasting Act, which gives it a public mandate which is a bit different than PBS). So basically by law the CBC has to be available to everyone in the country, everywhere (this didn't stop the CBC from advocating for fee for carriage for itself).

Originally the deal was the networks got the frequency, but they had to serve everyone. As "everyone" increasingly got cable or satellite, and audiences split up and started going to all the specialty/subscription channels, this became less of a good deal for a big broadcaster.

3a. In the US it seems to be possible to pick up channels like the CW over the air, whereas in Canada it would definitely be part of a cable package no matter where you lived. Is this because content production happens in the US, and so they have more negotiating power when they go to Canadian stations since Canadian stations want them so badly?

Because Canadian audiences are so small they're pretty insignificant to US interests, and in any case, the Canadian industry is regulated. You can pick up the American OTA channels (if you can get the signal), but no American-owned specialty/cable/subscription channels are allowed to operate in Canada. The ones that we get in Canada are always something like "HBO Canada" or "MTV Canada" and they are owned by Canadians (there's an exact percentage amount which is required to be Canadian ownership/funded) and must follow Canadian regulations.

Generally, the Canadian networks buy the rights to the most popular American programming , and the deal is that they get to "simulcast" the program with the American channel - so if the Canadian channel broadcasts the program at the same time as the American channel, Canadian viewers see only the Canadian ads (and the Canadian channel gets the ad revenue). If the Canadian broadcaster chooses to air the program at a different time, they lose out on that opportunity (and a Canadian broadcaster *will* occasionally buy the rights to a popular American program then fail to air the program at all, rather than see the rights go to a competing broadcaster).

The Canadians buy the expensively produced and popular American programming at the fraction of the cost at which it was produced in the US and aim to minimize, as much as possible, the Canadian content they have to broadcast (which will never approach the ROI of the American stuff, as they have to pay to produce it and the amount that they pay - the production budget - just won't ever be as much as the budget of a network American program). The only reason that the private networks produce and air Canadian programming, for the most part, is because they are required to by regulation. The exception to this being Quebec, where there is an audience for domestically produced programming. The CBC currently chooses to air a mostly Canadian lineup, although there have been points in the past when it actually aired a lot of American programming.

In the 90's, this meant that Canadian kids never got to watch MTV's The Real World (unless their parents had some kind of crazy illegal satellite hookup). In the internet era, not so much.
posted by scribbler at 7:25 PM on October 18, 2012

This has mostly been answered already, but I'll do my best to muddy the waters.

1. Technically there are two types of network stations, affiliates and owned-and-operated stations. Owned-and-operated stations are owned and operated by the networks, affiliate stations are not. Owned-and-operated stations only really show up in the larger markets. Affiliates are required to carry network content for certain time blocks, with some mix of local and national advertising in these blocks. For TV this is generally prime-time and late evening shows, radio is mostly just news shows and updates. During other blocks, the networks can show whatever they want: syndicated shows, news and other in-house produced shows, movies, infomercials, etc.

Public broadcasting is a bit different, the various member stations generally have a free hand to pick which shows they want and when to air them. Many public broadcasting stations also produce their own shows and sell them to other public broadcasting stations. Public broadcasting stations also don't make money from advertising, at least not in the way that commercial broadcasting does. Companies make donations to the stations and between programs they'll say that this show was brought to you by company X, company Y, and the Corporation for Public Broadcasting. Public broadcasting also gets money from listeners directly in the form of donations.

There are also unaffiliated stations which have no network content. For more information, see the Weird Al classic movie UHF.

1a. Generally stations have one network affiliation. Some smaller markets may have a station which carries more than one network's content, but this is much less common now that digital broadcasting allows stations to carry the different networks on multiple subchannels.

1b. The callsign systems are all based on International Telecommunications Union prefixes. The US gets (among others) K and W. Canada mostly uses CF-CK, although they managed to trick Chile into letting them use CB as well.

1c. For the specific example you gave, it is because many NPR shows are produced by the individual stations instead of the networks, commercial network programming is more likely to be associated with the network and not the station. Another issue is that station identification requirements vary by country, and I believe the US FCC requires more frequent station identifications than other countries.

1d. I believe this is more a function of commercial vs. public broadcasting than TV vs radio.

2. Channel numbers for broadcast TV correspond to certain frequencies, and there needs to be a physical buffer between different stations broadcasting on the same channel. So if a channel is skipped it's usually because there is another station with that channel close enough that they could interfere, even if you can't pick up the station where you are. Channels (and radio frequencies) are assigned based on availability and broadcaster preference. There is no connection between a channel 25 in one market and a channel 25 in another market.

3 & 3a. As far as what's available OTA and what isn't, it depends entirely on the number of over the air channels and what networks those channels decide to affiliate with. Less populated areas will tend to have fewer stations than more populated areas. Over the air broadcasting allows a station to reach a wider audience, but is inherently more overhead than just selling programming to cable. Going cable-only also allows you to skirt some FCC broadcasting regulations.
posted by ckape at 9:02 PM on October 18, 2012

One other tidbit you may have not known:

In the US, call signs for radio AND TV stations start with a 'W' if they are located east of the Mississippi River and 'K' if they are located west of the Mississippi River.

HOWEVER! This was not decided until the mid-to-late 20's, so there may be some stations (doubtful) that are W-whatever in, say, Kansas.

Good short history lesson on this here.
posted by kuanes at 3:44 AM on October 19, 2012

Wow, you guys, this is awesome. I hate being one of those people that mark 70%+ of the thread as best answers, but, well, you all really did answer my questions super well.

The only thing I can think of off the top of my head that doesn't quite make sense is why Canadian TV stations rebrand themselves into something other than callsigns--CityTV, CTV--whereas US stations refer to themselves more by the callsign? Like, I might ask someone how I can watch the presidential debate and their response might be "Oh, your best is PBS on UNC-TV" (thanks for the correction, ronofthedead). Is that just a "we've always done it this way" thing?

Anyway, thanks again to everyone who took the time to answer. This makes so much more sense than reading Wikipedia did.
posted by Phire at 7:55 AM on October 19, 2012

whereas US stations refer to themselves more by the callsign?

Local news branding and marketing, for the most part -- that's where the local stations compete most vigorously because it's their own content and identity ("Watch live local WBFK Eyewitness Action News 7 for more helicopters and MegaWeather!") and there's a purer choice* for viewers and local advertising budgets that doesn't exist with other programming. That isn't necessarily bound to the callsign -- WITI in Milwaukee is "FOX6" -- but it is bound to the affiliate.

Canada has more owned-and-operated local outlets, and a smaller population with wider media markets concentrated around urban centers: together, that encourages consistent branding across local and network programming. In that regard, it's closer to Australia than the US.

* It's not always a pure choice: some media markets in the US, especially ones that overlap state lines or cover two or more large cities, have affiliates located in different places and differentiate on that basis. But for big metropolitan markets, it's more or less straight competition.
posted by holgate at 10:02 AM on October 19, 2012

Also, "UNC-TV" is really an umbrella term for a set of individual stations, each with its own callsign (WUNL for the Triad, WUNG for the Charlotte area) that pool their resources to create a statewide PBS affiliate. A slender majority of states use this pooled system for public television, but there are also some big cities with independent as well as a statewide station, both affiliated to PBS, and other cities with more than one independent PBS affiliate.
posted by holgate at 10:21 AM on October 19, 2012

The call-sign system applies to Mexico, too. Mexican station call signs all begin with X.

There are American cities which are close enough to the Mexican border to be able to pick up stations with broadcast antenna located in Mexico, broadcasting under an X??? callsign, and back in the heyday of radio (the 30's and 40's) there were a couple of notorious stations which broadcast in English out of Mexico in order to evade FCC rules. (They mainly targeted San Diego and Los Angeles.)

AM radio has some unusual characteristics. Because the frequency is low (around a megahertz) and the wavelength is long (300 meters), the range changes at night as the "ceiling" lifts. As a result, an AM transmitter which might be able to cover one city during the day can be received from a thousand miles away at night.

An example of that is KSL-AM, Salt Lake City, and KXL-AM in Portland Oregon. Despite the similarities in the call letters, the two stations are not affiliated in any way. But they operate on the same frequency during the day. KXL's license doesn't permit it to operate at night, and here in Portland we can pick up KSL at night on that same frequency. (It's a "clear channel station".)

KXL isn't the only station having to do that. There are stations all over the western half of the US who have to shut down at night. KSL is the only one on that frequency who has a 24-hour license for the western part of the US.

That doesn't happen with FM (about 100 megahertz and a wavelength of about 3 meters) or TV (most bands of which are even higher frequency and shorter wavelength).
posted by Chocolate Pickle at 10:05 PM on October 19, 2012

Rats, my information is out of date. KXL-AM is now known as KXTG and no longer uses the same frequency as KSL.

What I described was how it worked when I was a kid.
posted by Chocolate Pickle at 10:09 PM on October 19, 2012

The only thing I can think of off the top of my head that doesn't quite make sense is why Canadian TV stations rebrand themselves into something other than callsigns--CityTV, CTV--whereas US stations refer to themselves more by the callsign?

It's possible that this is a result of laws regarding station identification. I'm having trouble tracking down specifics for Canada, but the US has pretty explicit rules about how stations have to legally identify themselves during the course of the broadcast day. A discussion here claims that Canadian stations only have to identify themselves once a day.
posted by god hates math at 6:36 AM on October 20, 2012