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Discussion Starter · #1 ·
We receive COMCAST digital cable in suburban MD, near Washington, DC.


I have amplified the cable signal (using an eLabs 2-way antenna amplifier with lower noise characteristics than what you usually see in consumer electronics stores, to cut the funny noise I had with them), split it, sent one half to the RNG110 set-top-box, and one half to an HDTV. I am feeding the box to the TV both through a composite video cable (NTSC, 480i) and through an HDMI cable. All the cables are shielded and reasonably short.


The HDTV is a $280 32" Westinghouse VR-3225, strictly bottom of the line by most of your standards. For example, some TV's have better noise filtering, and have better options for using the whole screen for NTSC signals, and can see the Internet. But the picture can be adjusted to be bright, detailed and colorful, supports 1080i and 1080p, and it looks nice as a computer monitor, which are all we cared about.


I looked at channels that are available on the cable box in HD form, and are available in both NTSC and HD form as clear (unencrypted) QAM channels when the box is bypassed.


The results are really quite intriguing! I expected the set-top-box to yield the best results, but that isn't what happens.


The set-top-box, fed to the TV in NTSC on a composite video cable (480i), is fairly clean, but is blurred, and it is hard to see details like pictures of text, such as when the picture contains a hand-written letter. (Interesting: many advertisements are not blurred, but appear quite sharp. I bet they use edge enhancement.)


The box doesn't look any better when it is fed to the TV through an HDMI cable, though the TV says it is receiving 1080i, and the picture is a wider.


The direct feed analog NTSC form looks far worse. In particular it is both very low detail and very noisy, pixel-to-pixel and frame to frame. The TV's noise filter can mostly clean the noise up, but it is still blurred. I wonder if the digital data impinges on the frequency range of the normal NTSC signal, and is somehow distorting the analog signal...


The direct feed clear QAM form (1080i for the channels I was looking at) is overwhelmingly cleaner and more detailed than anything else. It is easy to read pictures of text.


Does this make sense to anyone?


It does not make sense for a cable box to appreciably degrade the signal! Given that there is local competition from Verizon, as well as satellite competition from DISH TV and DirectTV, Comcast should be creating the best signal possible from its boxes, and I assumed they would do so.


The one thing I am not sure of is that the cable box was not leased as an HDTV-capable box. (Comcast doesn't charge any more for boxes that are, but this is what we have now. My TIVO can't handle HD, so I'm reluctant to switch to an HD box, in case it can't also deliver SD.) It does not look like the modern Comcast HD RNG110 boxes - but it does have the HDMI port, and that port does deliver some channels in 1080i. Is it possible the box down-samples the QAM signal, then upsamples it again to produce HDMI?


I have tried disconnecting the composite video cable from the cable box, on the assumption that producing that signal might put the box in a weird mode, and disconnecting and reconnecting the power plug to reset the box, but that changed nothing.


Can anyone give me reasons for what I see? For those with similar setups, is it consistent with what you see?


We would like to get an HD recorder, either TIVO or lease a COMCAST DVR.


But if Comcast boxes in general deliver poor signals, paying for an HD DVR, from TIVO or Comcast, is a complete waste of money.


(We can't limit ourselves to clear QAM channels, because that doesn't include several channels we like.)


I'm also wondering - do any of you use Verizon, Dish TV or DirectTV in the same geographic region? How good is the HD from these? Comcast is the most expensive, once the introductory offers have expired, as they have for us, so other options can be considered. (Though I think HD TIVO's don't work with DishTV or Direct TV.)


Thanks for any help!
 

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Quote:
have amplified the cable signal (using an eLabs 2-way antenna amplifier with lower noise characteristics than what you usually see in consumer electronics stores, to cut the funny noise I had with them),

When you state funny noise what do you mean, also did you have pixilation of the signal before you added the amp?
 

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Discussion Starter · #3 ·
I meant that when I bought the best antenna amplifiers that Radio Shack and Best Buy had to offer, they put lines and ghosts all over the image, similar to what you see when poor quality cables touch each other.


I looked up noise figures for antenna amplifiers, found the eLabs 6001A was the best I could afford, and bought it. Maybe lines and ghosts are more interference than noise, but it worked.


But now you've got me wondering: what if I don't amplify or split the signal, but feed the cable directly into the cable box? That's a little complicated, because the cable connector won't screw into the cable box (something about the lengths of the connectors), but maybe the amplifier is part of the problem? I'll try it.


But isn't the cable box signal based on the QAM signal it receives?
 

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Discussion Starter · #4 ·
OK, managed to connect the cable directly to the box. No improvement in composite video or HDMI outputs.


Of course, Comcast split our original cable input into Internet and TV. I don't feel up to undoing that split.


Besides, none of this explains why the clear QAM signal from the cable looks so much better than the box, input from the same cable.


I can think of only two possibilities: The individual cable box is not very good. Or no Comcast cable boxes are very good. Which one of these is true makes a big difference.


I'm very hesitant to exchange boxes without good reason. The first 5 Comcast boxes delivered to our home didn't work at all. It is possible the local (Lanham) Comcast office, or the contractors they use, has issues, or that set-top-boxes are generally unreliable.
 

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Are we comparing apples to apples here?


You mention that you are looking at the 1080i channels when viewing through QAM.


Are you sure that your box is an HD-capable box ... with a signal output of an HD signal?
 

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Sorry, but I didn't read your entire 1st post. IMO, call your cable provider to resolve.
 

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You mentioned internet!

Does that lock up okay if so:

Access the diagnostic page of your modem probably 192.168.100.1.

See what the power level and SNR is of the downstream signal is.

From the splitter you mentioned you can calculate the power hitting the STB.
 

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If you are no experiencing any pixelating or loss of picture, increasing or decreasing the signal levels will not make a difference in picture quality(in terms of sharpness,etc). Therefore the OPs signal levels at this point would be irrelevant.


If your box has an hdmi output, chances are it is an hd capable box. I would make sure you are actually comparing an hd channel to an hd channel and not just regular channel 3 to the hd version of channel 3.


In my opinion there seems to be a setup issue or a setting on the tv or box that is the issue as you should not see a considerable difference in picture quality using a cable box, regardless of the provider. Check your channels, the hd channels on the box are usually in the 800's or something like that, make sure your box is set to output in at least 720p and make sure your tv picture is not set to a zoom format.


If none of that works, I'd echo ratmans suggestion of calling the cable company. But I would anticipate a charge in this situation.
 

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Here in ATL, no difference at all in QAM and HD through the STB. Comparing apples to apples...ie ABC to ABC.
 

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Quote:
Originally Posted by MRG1 /forum/post/20828941


The set-top-box, fed to the TV in NTSC on a composite video cable (480i), is fairly clean, but is blurred, and it is hard to see details like pictures of text, such as when the picture contains a hand-written letter. (Interesting: many advertisements are not blurred, but appear quite sharp. I bet they use edge enhancement.)


The box doesn't look any better when it is fed to the TV through an HDMI cable, though the TV says it is receiving 1080i, and the picture is a wider.


The direct feed analog NTSC form looks far worse. In particular it is both very low detail and very noisy, pixel-to-pixel and frame to frame. The TV's noise filter can mostly clean the noise up, but it is still blurred. I wonder if the digital data impinges on the frequency range of the normal NTSC signal, and is somehow distorting the analog signal...


The direct feed clear QAM form (1080i for the channels I was looking at) is overwhelmingly cleaner and more detailed than anything else. It is easy to read pictures of text.


Does this make sense to anyone?

No. It sounds as if you are indeed seeing HD in Clear QAM, but not coming out of your STB. Is the blue light on the front panel illuminating? Have you followed the instructions on page 12 of your manual for setting the output resolution of your box? Manual instructions aside, I usually set the output resolution of the box to be the same as the native resolution of the TV. Try this if you are indeed getting a blue light on the front panel.
 

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Discussion Starter · #11 ·
Thanks, guys & gals! You were a lot of help.


For example, 4-0 was the analog NTSC signal, and 4-1 was a digital HD 1080i QAM signal, as seen directly by the TV tuner.


I set the box to channel 4, The TV said it was getting 1080i from the box on the HDMI cable. I assumed that meant it was deriving the signal from 4-1.


Not so!


I did indeed have to tune to an HD channel (based on the channel logo the station places on it's screen) to get real HD through the HDMI cable. (It could always receive those channels in SD through the composite video cable.)


---


The next question is: Can comcast detect the fact that we are using an HDMI cable to connect to an HDTV, and charge us extra for it?


We don't think HD is worth it if it costs extra.


As near as I can tell by looking at Comcast's extremely complex structure of web pages, they don't charge extra for HD boxes - which makes sense if they are really the same boxes, as this would seem to show - but I might have missed something, or there might be a hidden charge.


(I only ran this test for a minute or less, then powered off the box and disconnected the HDMI cable. Hopefully that won't create a charge.)


We could talk to Comast. But they haven't given correct answers about charges in the past. (E.g., digital cable was not supposed to cost extra. It didn't, at first. But then it did.) Possibly the local office isn't very knowledgeable about the service they sell.
 

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When I dealt with Comcast they did not charge extra for access to HD channels. However, they did charge extra to rent HD capable boxes. For example a digital cable box was $5/month, and an HD cable box was $10/month. A standard def DVR was $10/month, a HD-DVR was $15/month.
 

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There is no way that a provider can tell through their system what type of cable connection you are using on their boxes. The Hd version of the channel for comcast would be in a higher channel number (ie 1004). The SD will always be 4 for channel 4.
 

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Prices for service will vary from system to system. Where I'm at the box rentals are low but they charge for an hd access fee. It's usually around $10 total for an hd receiver but again this will vary.


Besides, if you weren't already paying for the channels you would not be getting them, so if you see them, you're probably paying for them. Ain't getting much for free nowadays, outside maybe the locals.


Either way I find hd worth it, I just can't watch SD programming on an hdtv unless I really have to, but most if not all the channels I watch are in hd now anyways. Hd service and a dvr are the two things I actually don't mind paying extra for, I can live without half the channels but couldn't live without either of them. But to each their own.
 

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They would get the locals in HD, and through Clear-QAM, without the box, but not stuff like USA, TBS, ESPN, unless they have the proper tier. I suggest that the OP contact Comcast regarding what plan they are on, if they do not have the info regarding it,
 

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Discussion Starter · #16 ·
Thanks guys!


We have trouble getting clear consistent info from the local Comcast office.


We are not alone. One of Comcast's local competitors has been taking advantage of that in their ads...
 

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Quote:
Originally Posted by MRG1 /forum/post/20847679


Thanks guys!


We have trouble getting clear consistent info from the local Comcast office.


We are not alone. One of Comcast's local competitors has been taking advantage of that in their ads...

The problem is so few of Comcast's subs ask about QAM, the CSR's don't know much if anything about it.


All Comcast systems have the local HD they carry, usually the HD shopping channels, and maybe one or two other HD channels like WGN America or TBS, in clear QAM format. The rest of the HD channels are encrypted.
 

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Discussion Starter · #18 ·
CSRs have given me accurate info about QAM, though they quite understandably won't say what channels are what.


It's getting consistent prices, and on establishing service in a minimal number of visits, where they fall down. Plus they offer introductory prices, which increase substantially, without the future increase being very clear, and the bills are very hard to interpret - bad psychology.


Once connected, their technical service has been excellent - fast, reliable Internet, reliable cable service, lots of available channels. They have a lot of things going for them. Many people are happy to pay for good service. All Comcast needs is good customer service to go with the solid technical service.
 

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Quote:
Originally Posted by MRG1 /forum/post/20848912


CSRs have given me accurate info about QAM, though they quite understandably won't say what channels are what.


It's getting consistent prices, and on establishing service in a minimal number of visits, where they fall down. Plus they offer introductory prices, which increase substantially, without the future increase being very clear, and the bills are very hard to interpret - bad psychology.


Once connected, their technical service has been excellent - fast, reliable Internet, reliable cable service, lots of available channels. They have a lot of things going for them. Many people are happy to pay for good service. All Comcast needs is good customer service to go with the solid technical service.

Very level headed take on the situation. Well put.
 
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