I read the post about QAM – or Quadrature Amplitude Modulation— here: http://club.cdfreaks.com/f149/overview-qam-hd-signal-compression-mpeg2-242503/
I have Expanded Basic Digital TV.
I have a few specific questions about QAM. I have Time Warner with a very long history of things I have fought bitterly about with ongoing signal problems such as:
– pixelation – mostly evening and over-night times — this may or may not take out the whole pic / sound for minutes to hours to days; worse during rain or after rain
– pixelation of whole screen when the EBS–Emergency Broadcast System banner goes out from Cleveland Ohio for bad weather alerts – 3/ths of screen turns to a sideways pixel of plaid-looking colors, green, black, majenta in a weird pattern… stays long after the EBS alert goes off
– The EBS banner --LoOKs LiKe tHe WoRdS JumP LiKe an OLd TicKEr TaPe – does it the entire time, jumps up and down as each letter appears singlely on the banner
– Digital sound break-up, sounds just like a digital phone but it’s the TV (I don’t have that kind of phone)
– sound not matching moving mouths, up to 5-10 second sound delay
– sound stopping completely but picture still moves
– sound stopping followed by picture stopping OR going to black (with Cable TV banner staying)
– sound & picture staying off for hours
— (all these things usually come back by themselves either minutes or hours later).
– a picture artifact, like dragging waxed paper across the picture, so it’s blurred-- but this happens very fast and returns to normal.
We’ve run the gambit trying to fix these issues: replaced inside cable wiring; replaced outside cable wiring JUST TO the pole/to the drop; test for electrical interference (none); tested for Hrtz portable phone interference (none); replaced analog box (I have analog-based TV, “new” 5 yrs ago) with Digital Service and Set Top Box; break out (split) the plant node to my neighborhood because of customer high saturation/usage; occ. fixes of a loose fitting or wire in the drop—but they won’t replace the amplifier ON the pole, or the 2nd amplifier diagonally from my house. The Amplifier housing (the box on the pole) fills with water during rain/snow thaws; fills with ice during winters. Summer/dryer season the problems decrease. Been fighting for years. They previously tried to “fix” the issues by selling me a digital set top box-- but still had trouble.
So to “repair” all those issues, they put in a (supposedly) never-used-by-anyone-new digital Set Top Box (“the box”). The new box was installed by the company less than 2 months ago and every AM around 2AM to 3:30AM the TV goes OUT-- black screen, no banner. Sometimes it will have words pop on screen: “No Signal” or “Low Signal”. Minutes or hours later, the set comes back on. The BOX looks normal-- it does NOT re-load the box; the box never really went off, it just is not delivering a signal to the TV.
Cable Company has software that lets phone techs ‘see’ the Box’s levels. Most nights when I’ve called bc the screen went black, the “Whole House Check” and “Set Top Box” software reports the box “has no Mac Address” and that the box is not communicating back to the Time Warner plant-office machinery. Tonight, the software would not even show I had a box for over 30 minutes (the pic-sound had only been out 2 minutes, but 30+ minutes later the cable box was not showing on the company’s equipment).
Finally, the “Whole House Check” and “Set Top Box” software ‘saw’ the box again … and showed “Bad QAM”. All other signals were A-ok, it said.
So I understand QAM is used to compress signal so more channels can be sent in the same bandwidth, and that the QAM unit/thingie is inside the Cable Set Top Box.
If I have an intermittent drop in signal from T-W, would the ONLY problem be 1. the QAM unit going bad? OR 2. the QAM reports bad because the signal drops too low? OR 3. the problem is BOTH an intermittent low signal AND bad QAM??
Does the bad amplifier on the pole play any role in having “bad QAM”?
Is there some machinery in the Time warner “Head End” or plant-node that also has QAM ‘units’ built in? Should the Head End/Op folks be checking QAM levels in their equipment?
- What else --in addition to bad QAM—might explain the list of picture and sound ongoing problems?
Also I read either here http://www.tech-faq.com/quadrature-amplitude-modulation.shtml
that cable companies Mux (spelling?) the signal so that one of several stations sent in the same bandwidth is allowed to “spike” higher than the other channels. Does that play into the “bad QAM” problem?
Lastly, NO sleep timers have ever been set on this TV or on this or any Cable Set Top Box. What might explain WHY the picture-sound loss, with loss of Mac Address and no communication from the box to the company, that ONLY occurs between 2 AM and 3:30AM – typically closest to 2AM & 2:15AM. Company states NO upgrades or maintenance being done at those times to the local node (closest work is 3 hours away), and states they are NOT automatically checking or re-setting boxes at that time of morning.
When they do in-house repair calls mid-afternoon, everyone says the signals are within normal limits. Only other recent problem was that the “correction ratio was climbing”. Besides Expanded Basic TV, I have Broadband Internet with frequent drops/loss of connection.
Sorry such a long post. But I’ve fought the Cable Company and I like to have correct technical info before I try to fight AGAIN for them to fix these problems.
Thank you for any expert analysis or general ideas you can give.