22-8 22-9

July 28, 2009 6:55 AM

What's with these mysterious, over-the-air, digital television channels?

I just installed a better television antenna and when I scanned for new broadcast channels, among the ones my tuner found were 22-8 and 22-9. Both have excellent signal, but don't seem to be broadcasting anything.

And what's up with the -8 and -9? Every other digital channel is -1 -2 or -3...

Austin, TX.

Should I stay tuned into them and wait for the messages to start?

posted by dirtdirt to technology (14 comments total)

(when I Google for 22-8 and 22-9 all I get are random parts and bible verse - "He that soweth iniquity shall reap vanity: and the rod of his anger shall fail" is pleasingly, uh, Biblical, but I don't reckon it's actually pertinent.)
posted by dirtdirt at 6:55 AM on July 28

digital channels are represented as 22.8 or 22.9, not 22-8. Looks like 22.9 is supposed to be a PBS station.
posted by billysumday at 7:00 AM on July 28

The digital television standard allows multiple video streams on one station's carrier. So channel 22 is using streams 8 and 9.
posted by leapfrog at 7:02 AM on July 28

See also: ATSC, the digital broadcast television standard in use in the US.
posted by leapfrog at 7:04 AM on July 28

The only reference to "22.9" that I see in the PDF that billysumday linked to is to a power output of 22.9 kW, and that's not a channel number.
posted by Nothlit at 7:06 AM on July 28

ha! yes, i didn't even see that. who is your cable provider? that could help us determine what the channels are. chances are, the station that owns 22 (like ABC or NBC) is sitting on those auxillary channels. maybe some day in the future they'll have an NBC all-weather digital stream, or a music channel, or local news only or something. for now they're just sitting on them.
posted by billysumday at 7:12 AM on July 28

and also, what exactly is channel 22? NBC, ABC, CBS, PBS?
posted by billysumday at 7:12 AM on July 28

okay, so this is weird. apparently channel 22, the pbs station, is displayed as channel 18. i don't really get that. but that's what the wikipedia entry for klru says. and you have three visible digital PBS stations (18.1, 18.2, and 18.3).
posted by billysumday at 7:20 AM on July 28

I don't have any cable, all my TV is antenna. 18-1, -2 and -3 are the PBS stations (KLRU, KLRU2 and KLRUQ).

There is no 22, and has not been since I lived in Austin.
posted by dirtdirt at 7:34 AM on July 28

On April 16, 2009, KLRU ceased analog broadcasts. Its digital signal remains on channel 22 using PSIP to display "18" as its virtual channel number

Hmm, from the Wikipedia article on KLRU. So I guess 22-8/9 are some sort of vestigial digital remnant - the place that the signal for the 18's is broadcast from, but doesn't show up as anything on its own?
posted by dirtdirt at 7:38 AM on July 28

22.8 and 22.9 are part of the UpdateTV service, which allows TV firmware upgrades to be sent over the air.

This is broadcast on PBS stations around the country. We see the same thing in Houston on 8.8 and 8.9.
posted by Gridlock Joe at 7:51 AM on July 28

dirtdirt: "And what's up with the -8 and -9? Every other digital channel is -1 -2 or -3..."

These numbers (nn.m or nn-m) are called Logical Channel Numbers (or more often Virtual Channels in the US). The technical specification (PDF) says that the part after the decimal/hyphen "indicates the broadcaster preference for ordering services". It's a ten-bit field, and values between .1 and .999 are valid.

The choice of -8 or -9 versus -1 or -2 appears to be simply arbitrary.
posted by Plutor at 8:30 AM on July 28

We've been trying to figure out where our HD is coming from. We don't pay for it, don't have an antenna, and I'm not sure if our TV has a built in tuner. I think it does.

Like, I get channel 11, which is a pittsburgh channel not in HD. Pressing channel up brings me to 11-1, which is high def. I cannot press any series of keypresses that will take me to 11-1 automatically, however flashback works.

Channel 13, again the pittsburgh pubtv channel, has 13, 13-1, 13-2, 13-3. The first two dashes are high-def pubtv. The third one, 13-3, is something called RTV, which seems to play old british shows all day long.

We get one of each network in high def, even though we have two channels of some networks. None of the cable channels have dash channels.

After channel 7, we get 7-1. Pressing up again takes us to something like 7-5333-71, which is yet another channel all together.
posted by TomMelee at 12:04 PM on July 28

I have seen this happen. The above posters are correct. Digital TV just sends out a digital stream of information. That stream can be 1 big, beautiful, HD program, or it can be 20 crappy channels of infomertials. The (plutor's) logical channel information is put in there so you can:

1- Tune the different streams. It would be super complicated for everyone if each stream was its own channel number, so they did the xx.yy thing.

2- Even though the digital stream might be broadcast on some unrecognizable channel number, the TV stations wanted to make sure there was a mechanism for people to know that "ol' reliable ABC 7" is still channel 7. So the stream can come across on any channel, and in that stream is the data that says "OK, call this stream 7.1, this other one 7.2".

Those can get messed up- I have had instances where channel 7 appeared on 7.1 and also 47.1 (the actual frequency they were broadcasting on). The logical data got messed up and confused the tuner. Presumably, it is either that update tv thing, or their PSIP machine is messed up.
posted by gjc at 8:02 PM on July 28