What's up with TWC QAM?

[Martyus]

I setup my new HDTV last week and was able to get all the local digital/HD channels from the TWC feed (I have the basic/standard analog package). The local QAM HD channels were found on 0.504 (NBC), 0.506 (FOX), 0,512 (ABC), etc. The TV reported a strong signal (3-4 bars out of 5) for these channels and everything was woking fine.

Sometime between 5:30pm-6:00pm on Tuesday, Jan 1, all the 0,5xx channels dissappeared!! I did a channel scan and the local channels were scattered. I found ABC on 85.12, but the signal was poor and kept breaking up (1 out of 5 bars). The only watchable channel was FOX on 113.1 (as I recall).

Now tonight, Wednesday, Jan 2, all the 85.x channels are gone and I was able to find ABC at 0.512, but there is no FOX on 0.506, etc. I haven't yet done another channel scan to find the rest of the local HD channels. Also, the signal for 0.512 is weak (1 out of 5 bars) and the image/audio breaks up continuously.

What's going on here? Why are the channels shifting? Why is the signal so bad? Has anyone else seen this? Is this typical for QAM channels, or just some one-time quirk I am seeing?

I am planning to set up a Vista Media Center computer with something like an HDHomerun tuner to get the QAM HD channels. However, if the QAM HD channels are unstable, weak, and shift like this, it will be a pain to keep the channels mapped into VMC.

[kevbeck122]

Your TV is mapping the channels to their virtual numbers (what they are if you had a box).  I've only seen TWC switch the QAM channel numbers once back when they added the HD versions of 18 and 24.  It may be an issue where TWC is messing up the PSIP data which tells your TV the virtual channel number.  

I've used an HDHomerun on TWC QAM for a few months on Vista Media Center without problems.

[Martyus]

Ok. I guess I will have to keep playing with the channel scan to see if the QAM channels get stable.

Regarding the HDHR tuner, I have just started to read about it. I have been experimenting with a VMC computer with a HVR-1600, but it won't do QAM in VMC, so it is stuck to an antenna only.

For the HDHR tuner, how do the QAM channels get mapped into the VMC channel guide for recording and such?

[kevbeck122]

Last time I used one was a few months ago, so they might have changed something.  I know when they first supported QAM in media center earlier last year it was pretty much completely manual... a major PITA.  You had to create a text file mapping each  QAM channel to a media center virtual channel.  When I started using it again a few months ago, the process was more automated... everything was pretty much done for you, so the media center setup was almost as easy as setting it up with an antenna.  The channels are mapped to whatever channels are available in the 1000 range.  They won't be the correct number for whatever channel (ie: NBC might be 1015 instead of 1041).  I believe they let you choose the order of the lineup and possible which channel it is associated with.  There is a decent write up on the setup: http://www.silicondust.com/wiki/hdhomerun/instructions/mce_cable.

[Martyus]

Thanks for the link. I am starting to understand how the HDHR works now.

Back to the TWC QAM reception. The only local QAM channels I have been able to get tha last couple of days are ABC (0-512) and CBS (0-505). However, the reception on these channels is spotty at best (frequent pixelation/audio drop). Channel 0-518 is there, but is continually pixelated with choppy audio and generally unwatchable. I can't find FOX or NBC on any available QAM HD channels.

Interestingly, at about 11:30pm, Thursday, Jan 3, the 0-5xx channels again disappeared and shifted to 85-12 and 85-05!

Does anyone know what is going on?
Why have I lost most of the local QAM channels in the last couple of days?
What is up with the unstable channel mapping?

Since I was able to get stable QAM channels in the 0-5xx range for almost a week (a week ago), I would tend to discount any problems with the tuner in the HDTV.

That leaves the TWC signal. Could a weak cable signal cause some channels to drop out completely? I had thought that digital TV was all or nothing (but I am getting some QAM channels).

Do I need to contact TWC?

[nick3092]

Thanks for the link. I am starting to understand how the HDHR works now.

Back to the TWC QAM reception. The only local QAM channels I have been able to get tha last couple of days are ABC (0-512) and CBS (0-505). However, the reception on these channels is spotty at best (frequent pixelation/audio drop). Channel 0-518 is there, but is continually pixelated with choppy audio and generally unwatchable. I can't find FOX or NBC on any available QAM HD channels.

Interestingly, at about 11:30pm, Thursday, Jan 3, the 0-5xx channels again disappeared and shifted to 85-12 and 85-05!

Does anyone know what is going on?
Why have I lost most of the local QAM channels in the last couple of days?
What is up with the unstable channel mapping?

Since I was able to get stable QAM channels in the 0-5xx range for almost a week (a week ago), I would tend to discount any problems with the tuner in the HDTV.

That leaves the TWC signal. Could a weak cable signal cause some channels to drop out completely? I had thought that digital TV was all or nothing (but I am getting some QAM channels).

Do I need to contact TWC?

My Sony finds the QAM channels under 0.506, 0.512 etc... but my Westing house has ALWAYS seen them as 85..1, 85.3, etc...  So it could possibly have something to do with the mfg of your tuner.  But, if your worried it's a signal strength issue, if you have road runner, and you have the Motorola modem (other modems can do this too, check http://www.speedguide.net/broadband.php for instructions) it has a built in signal strength meter.

For the Moto just point your web browser to 192.168.100.1 and go to the signal tab.  assuming your modem is on the same splitter as your TV, it should give you the same readings that your TV has.  Or you can temporarily move your modem and hook it up where the TV is.  I have perfect reception and my readings are:

Downstream SNR: 35dB (higher is better for this)
Downstream Power: -4dBmV (the closer you are to 0, the better)
Upstream Power: 52dBmV (the lower the better)

The downstream numbers are probably what your most concerned about.  The upstream is really an indication of how much power the modem has to use to communicate back tot he cable co, and doesn't mean that much for TV reception.  Hope that helps.  Also, read my rant on TWC's QAM service on the ""Where did PBS Go" thread.

[browndeermythtv]

I am planning to set up a Vista Media Center computer with something like an HDHomerun tuner to get the QAM HD channels. However, if the QAM HD channels are unstable, weak, and shift like this, it will be a pain to keep the channels mapped into VMC.

I've been using MythTV for over a year.  Until about six months ago, I was recording local channels (minus 18 and 24) off of TWC QAM.  TWC re-arranged the channels just one too many times on me, and I broke down and bought an indoor antenna.  I have good signal on every local channel, except channel 10, which is due to it being broadcast on VHF, and my antenna being UHF only.

I am considering a different antenna.  If TWC offered even one non-local non-PBS channel in QAM, I might be tempted to return to TWC QAM, but I am not holding my breath, but I do not miss having to re-scan, re-cull, and re-map the QAM channels every six or so months.