Lost NBC HD channel on TWC

DickR · 02-06-2012, 03:53 PM

We have TWC for TV service. Last night I found that among the channels our digital TV channel scan had found was NBC on 83.3, and there was the super bowl in high def, full screen! At around actual kickoff time, the screen went blank, and we had to switch to channel 6 and watch in low def. What happened? Some other HD channels still were functioning.

Somewhere I was told that the cable network acts like a giant antenna, and that the TV was picking up the over-air signal in the channel scan, but I don't know if that is correct, given that the cable is coaxial and is supposed to be free of outside interference. Did TWC do something sneaky?

brk-lnt · 02-06-2012, 04:22 PM

If the cable system is acting like a "giant antenna" then something is seriously wrong with the system.

Most modern cable systems use a dynamic channel frequency mapping. On your cable box it may always say that Channel 123 is NBC-HD for example, but the cable box is remotely programmed to make Channel 123 correspond to different frequencies. This can happen for a number of reasons, one of which could be allocating bandwidth for cable modem usage. Cable modems "steal" bandwidth/frequency from what can be used to carry TV, so there is a constant tradeoff/balance to be had.

About 8 years when the systems were first going digital, and digital tuners were not very common, many of the on-demand shows were just mapped to upper frequencies. You'd watch The Sopranos on-demand, and the cable head-end would make the equivalent of Channel 1000 for your request and tell your cable box to tune that frequency (even though it would look like you were still on channel 1 or channel 99 or whatever). During these times you could see what your neighbors ("neighbors" being people on the same node as you, not just your street) were watching by scanning these upper channels with a QAM tuner card. You'd also see them pause/rewind/fast-forward as well, since all that happens at the head-end. In many cases you can still do this in hotel room cable systems if you have a laptop and a USB tuner card for instance.

Anyway, not sure why TWC changed the channel mappings, but it was probably for some relatively uninteresting reason.

BroadHopper · 02-06-2012, 04:57 PM

I am assuming TWC = Time Warner Cable.

I have Metrocast with no cable box. However I have a QAM tuner on which I am able to access the digital channels. For instance 6-1 is channel 6 high def and 6-5 is channel 6 digital as well as 6 for channel 6 analog signal.

Metrocast as of January 31st discontinue channel 6 because channel 7 braodcast the same affiliate. They also discontinue Channel 8 because channel 9 is the same affiliate.

However, I am able to get channel 6 and 8 digital and the analog channels are gone. I was able to watch the game on channel 6 HD even though the folks with cable boxes could not.

I also notice to the higher channels 95-100 if someone in the neighborhood is watching an on demand or PPV, i can pick the signal up.

I always use channel 8 weather as I find the weather forecast a lot more accurate than channel 9

rick35 · 02-06-2012, 07:39 PM

I believe cable companies are required to carry local channels in HD. Before I added an HD box to my kitchen TV I was able to get 4,5,7,9,11,25,38 and 56 in HD in the clear. You have to scan for channels and you should find them. When I first tried it the Comcast scan resulted in odd channels like 83.3. Now they use 7.1 for channel 7 in HD. The odd channels were the primary reason for adding the HD box.

wifi · 02-06-2012, 07:41 PM

Portland Channel 6 requested a block on other NBC stations during the game, its their market area, so by law they had the right.

Please don't shoot the messenger

DickR · 02-06-2012, 09:24 PM

Just to fill in a few more things:

I noticed this afternoon that 83.3 again was live.

One TV, an older analog TV, has the cable box attached to it. The wide screen digital TV (newer) is just plugged into the cable outlet on the wall and thus is limited as to number of channels it can access. The channel scan picked up the various HD channels available, and they show as nn.m (up to three digits after the decimal point). From what has been said, I presume Time Warner Cable puts those out on its cable.

02-06-2012, 03:53 PM	#1
DickR Senior Member Join Date: Apr 2008 Location: Moultonborough Posts: 736 Thanks: 4 Thanked 255 Times in 167 Posts	Lost NBC HD channel on TWC We have TWC for TV service. Last night I found that among the channels our digital TV channel scan had found was NBC on 83.3, and there was the super bowl in high def, full screen! At around actual kickoff time, the screen went blank, and we had to switch to channel 6 and watch in low def. What happened? Some other HD channels still were functioning. Somewhere I was told that the cable network acts like a giant antenna, and that the TV was picking up the over-air signal in the channel scan, but I don't know if that is correct, given that the cable is coaxial and is supposed to be free of outside interference. Did TWC do something sneaky?

02-06-2012, 04:22 PM	#2
brk-lnt Senior Member Join Date: Aug 2007 Location: South Down Shores Posts: 1,939 Thanks: 534 Thanked 568 Times in 334 Posts	If the cable system is acting like a "giant antenna" then something is seriously wrong with the system. Most modern cable systems use a dynamic channel frequency mapping. On your cable box it may always say that Channel 123 is NBC-HD for example, but the cable box is remotely programmed to make Channel 123 correspond to different frequencies. This can happen for a number of reasons, one of which could be allocating bandwidth for cable modem usage. Cable modems "steal" bandwidth/frequency from what can be used to carry TV, so there is a constant tradeoff/balance to be had. About 8 years when the systems were first going digital, and digital tuners were not very common, many of the on-demand shows were just mapped to upper frequencies. You'd watch The Sopranos on-demand, and the cable head-end would make the equivalent of Channel 1000 for your request and tell your cable box to tune that frequency (even though it would look like you were still on channel 1 or channel 99 or whatever). During these times you could see what your neighbors ("neighbors" being people on the same node as you, not just your street) were watching by scanning these upper channels with a QAM tuner card. You'd also see them pause/rewind/fast-forward as well, since all that happens at the head-end. In many cases you can still do this in hotel room cable systems if you have a laptop and a USB tuner card for instance. Anyway, not sure why TWC changed the channel mappings, but it was probably for some relatively uninteresting reason. __________________ [insert witty phrase here]

02-06-2012, 04:57 PM	#3
BroadHopper Senior Member Join Date: Oct 2004 Location: Laconia NH Posts: 5,518 Thanks: 3,122 Thanked 1,090 Times in 784 Posts	cable companies I am assuming TWC = Time Warner Cable. I have Metrocast with no cable box. However I have a QAM tuner on which I am able to access the digital channels. For instance 6-1 is channel 6 high def and 6-5 is channel 6 digital as well as 6 for channel 6 analog signal. Metrocast as of January 31st discontinue channel 6 because channel 7 braodcast the same affiliate. They also discontinue Channel 8 because channel 9 is the same affiliate. However, I am able to get channel 6 and 8 digital and the analog channels are gone. I was able to watch the game on channel 6 HD even though the folks with cable boxes could not. I also notice to the higher channels 95-100 if someone in the neighborhood is watching an on demand or PPV, i can pick the signal up. I always use channel 8 weather as I find the weather forecast a lot more accurate than channel 9 __________________ Someday may never be an actual day.

02-06-2012, 07:39 PM	#4
rick35 Senior Member Join Date: Mar 2008 Location: Bear Island/Merrimack Posts: 711 Thanks: 56 Thanked 170 Times in 104 Posts	I believe cable companies are required to carry local channels in HD. Before I added an HD box to my kitchen TV I was able to get 4,5,7,9,11,25,38 and 56 in HD in the clear. You have to scan for channels and you should find them. When I first tried it the Comcast scan resulted in odd channels like 83.3. Now they use 7.1 for channel 7 in HD. The odd channels were the primary reason for adding the HD box.

02-06-2012, 07:41 PM	#5
wifi Senior Member Join Date: Jul 2007 Location: Lakes Region Posts: 1,321 Thanks: 282 Thanked 287 Times in 169 Posts	Portland Channel 6 requested a block on other NBC stations during the game, its their market area, so by law they had the right. Please don't shoot the messenger

02-06-2012, 09:24 PM	#6
DickR Senior Member Join Date: Apr 2008 Location: Moultonborough Posts: 736 Thanks: 4 Thanked 255 Times in 167 Posts	Just to fill in a few more things: I noticed this afternoon that 83.3 again was live. One TV, an older analog TV, has the cable box attached to it. The wide screen digital TV (newer) is just plugged into the cable outlet on the wall and thus is limited as to number of channels it can access. The channel scan picked up the various HD channels available, and they show as nn.m (up to three digits after the decimal point). From what has been said, I presume Time Warner Cable puts those out on its cable.