CanesFan95
Analog already is interoperable.
I think they're called "sub" channels, like 8-2, 8-3, etc. Do they all share the same frequency? Or is each one it's own separate frequency and RF transmission?
Are TV Sub-Channels All On The Same Frequency?
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They are multiplexed (combined) into a single data stream/ one transmission.
CanesFan95
Analog already is interoperable.
How many sub-channels can they fit? Sometimes I'll see like only 3. Other times there's 10. Usually, the first main channel is the main network like NBC, FOX, and so on. Is there any reason they can't all be 1080i?
depends
en.wikipedia.org
Digital television - Wikipedia
en.wikipedia.org
dosboot
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It depends on the configuration of the system;
so the TV station where I work has NBC, ABC in HD plus three SD channels. Note that ABC, FOX Transmit a 720 signal to affiliates so that does leave more room for additional channels (not sure how much) Also MPB broadcast Has three channels plus and all audio feed of the radio station. Technology is always advancing so more broadcasters can get more content overs the air and on screens.
CanesFan95
Analog already is interoperable.
So the signal strength is the same on sub channels? If you get like 9-1 or something, 9-2, 9-3, 9-4, etc. are the same signal?
Exactly, all or none.
While ATSC 3.0 is on the air in some markets, most people are watching ATSC 1.0 (I'm not discussing cable, fiber nor satellite). That stream is 19.3MB/s in speed. The number of "channels" you can fit into it depends on how much bandwidth each channel consumes. A HD channel will take a lot more than an SD channel, for example. Each audio stream included (multi-lengual for example) also takes up some of the bandwidth.
There all sorts of parameters that determine the bandwidth that will be consumed. MPEG-2 uses I, B & P frames. One will contain "all" the information for a frame, while the others just "modify" the data (they only contain changes). How often do you insert one of those frames vs just transmitting changes determines bw usage. Then there is bit rate. This is how cable companies "fit" a HD signal into a slot that has lower bandwidth, they reduce the bit rate of the signal. There is a lot to discuss on this topic alone.
But as I write this the industry is moving toward deploying the non-compatible ATSC 3.0 standard. There's quite a few changes. ATSC 1.0 was tied to MPEG-2 compression, ATSC 3.0 is not. ATSC 3.0 uses the same transport protocol as used by the Internet (think of receiving broadband Internet signals from an OTA TV signal). The poor 8VSB modulation standard of ATSC 1.0 will be gone in favor of one that better suits mobility of receivers and mitigates tons of issues.
There all sorts of parameters that determine the bandwidth that will be consumed. MPEG-2 uses I, B & P frames. One will contain "all" the information for a frame, while the others just "modify" the data (they only contain changes). How often do you insert one of those frames vs just transmitting changes determines bw usage. Then there is bit rate. This is how cable companies "fit" a HD signal into a slot that has lower bandwidth, they reduce the bit rate of the signal. There is a lot to discuss on this topic alone.
But as I write this the industry is moving toward deploying the non-compatible ATSC 3.0 standard. There's quite a few changes. ATSC 1.0 was tied to MPEG-2 compression, ATSC 3.0 is not. ATSC 3.0 uses the same transport protocol as used by the Internet (think of receiving broadband Internet signals from an OTA TV signal). The poor 8VSB modulation standard of ATSC 1.0 will be gone in favor of one that better suits mobility of receivers and mitigates tons of issues.
No it's not always on the same RF channel. In some TV markets, like here in Boston, where a company owns two signals, the sub channels are actually split amongst transmitted signals. "2.1" and "44.1" are on VHF 5, while "2.2, 2.3, 44.2" are all on UHF 32. "15.1 and 15.2" are on UHF 32, while "15.3" is on UHF 29. This happens in some other markets too, but is more the exception than the norm. Usually they are all on one RF channel.
Your best bet is to search the market using Wikipedia. The TV listing of which subs which are on which channels are typically very accurate there.
Your best bet is to search the market using Wikipedia. The TV listing of which subs which are on which channels are typically very accurate there.
CanesFan95
Analog already is interoperable.
Yeah, and the channel numbers are stupid confusing. I've got a local station WWSB that displays a logo '7' with the round circle thing, but they're channel 40 on the TV. But then you go deeper in the TV system settings and it says its "Physical Channel 24".
And you try looking up tower maps online and the channel numbers are all over the frickin' place.
And you try looking up tower maps online and the channel numbers are all over the frickin' place.
In my area, one transmitter emits 19.1, 64.2, 19.3 & 19.4; while another transmitter emits 64.1, 19.2, 64.2 & 64.3. It's so that someone who wants to watch main programming from either 19 or 64 can get it from one of two towers.
With regard to "tower maps" and such web sites; yes they are very bad right now. We've gone through something called repacking which elminated over-the-air physical frequencies of 37 to 51 (52 to 69 and 70 to 83 were already eliminated). All over-the-air TV signals must now fit onto channels 2 to 36. To make it even more interesting, they're rolling out the ATSC 3.0 incompatible standard, so for some time signals might be duplicated (one signal of ATSC 1.0 and one of ATSC 3.0).
I've scanned and mapped signals in my viewing range and no web site correctly lists them (that I've found). If a site shows physical channels above 36, you know they have not been updated.
With regard to "tower maps" and such web sites; yes they are very bad right now. We've gone through something called repacking which elminated over-the-air physical frequencies of 37 to 51 (52 to 69 and 70 to 83 were already eliminated). All over-the-air TV signals must now fit onto channels 2 to 36. To make it even more interesting, they're rolling out the ATSC 3.0 incompatible standard, so for some time signals might be duplicated (one signal of ATSC 1.0 and one of ATSC 3.0).
I've scanned and mapped signals in my viewing range and no web site correctly lists them (that I've found). If a site shows physical channels above 36, you know they have not been updated.
Most wikipedia pages are fairly accurate. Just look up the callsign.
WWSB - Wikipedia
en.wikipedia.org
KTFK-DT - Wikipedia
en.wikipedia.org
KUVS-DT - Wikipedia
en.wikipedia.org
Lists of television stations in North America - Wikipedia
en.wikipedia.org
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