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Digital TV Question w/ DBS

1740 Views 7 Replies 6 Participants Last post by  MarkA
I have Dish Network and have been contemplating getting a new TV. The current TV is just a '93 Mitubishi using S-Video input from the E* receiver. If I get a new TV, I would like to check out the Digital TV OTA signals just to see how their PQ is.

My question is, am I already receiving DTV by using the DBS? I know that it is not HDTV, but still isn't DTV different than the regular analog?

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Digital television is defined as being one of the 18 (?) formats defined as ATSC, as opposed to the current NTSC that most people watch now. Except for the high definition channels, the channels that you receive from DBS are NTSC, not ATSC, and therefore not considered to be digital channels.

Now, the channels are a digital signal, but a digital NTSC one. It's confusing, I know - and cable companies are taking advantage of that confusion making the claim that digital cable is the same thing as digital television.

Digital tv stations broadcast either upconverted NTSC (to 1080i or 720p), 480p (Fox High Resolution), 1080i (CBS, NBC High Definition). or 720p (ABC, WB High Definition). Upconverted looks slightly better than standard definition, 480p looks slightly better than upconverted, and 1080i and 720p will absolutely knock your socks off it looks sooooo much better.

You would know HDTV if you saw it! It's like looking out your window. :D
DTV uses 8vsb modulation (the same as HDTV) - in fact, you can look as DTV being a prerequisite to HDTV. DTV is not exactly what you are getting from E* now - most likely, what they do for your local stations is to digitize the analog signals and eventually your satellite receiver converts the digital stream back into analog for your TV.
NTSC is an analog signal.

DBS and ATSC are digital MPEG-2 encoded signals. DBS is 480i which is what the NTSC digitizes into (approximately), which in fact is an ATSC standard signal. ATSC has a bunch of formats ranging from 480i to 1080p. The common HDTV ones are 1080i and 720p.

Now the thorny issue is the transmission. Over the air HDTV uses a modulation of 8vsb which is just a method of sending a digital signal through the 6Mhz spectrum that the station uses.

Dishnetwork uses QPSK (an old satellite standard), and will be putting in 8PSK for newer signals for HDTV transponders. There are even faster standards available, but the limitation on the standard is the power per satellite transponder and the size of the recieving dish. Dish satellites have gotten much more powerful so they are now able to pack in more bits and your small dish can distinguish them from background noise. The next step up in power they could use 16QAM.

Cable companies use modulations such as 16QAM and 64QAM. This is because they have a nice sheilded cable and can pack in even more bits.

Another thing to note is that the spectrum for over the air TV is not contiguous. There are big gaps between some channels for things like FM radio.

Now the problem is that there is no standard established yet for cable reception of HDTV without using a cable box yet, since each cable box would use its own private method. One of the main holdups of this has been copyright holders wanting copy protection on everything.

Hopefully soon they will have a standard for "Cable Ready" ATSC that TV makers can use to make TVs that will work without a cable box. What is the point of having a digital tuner in your set if you cannot use cable without a box doing the tuning for you.

Another note: even though DBS is digital television at 480i, it does not mean that they do not overcompress the signal and give a bad picture. You may not have analog snow, sparkles, ghosting, etc, but your picture can now have digital artifacts such as blockiness, soft picture, etc.

The claim is that 4mb/sec is what it takes for broadcast quality for a 480i picture. This is about 8 channels per transponder. But, over time they have crammed 12 channels per transponder dropping the bit rate down to about 2.5mbs. Although they claim that the compression is better now (improvement in compression technology), the picture is suffering right now as they pack them in (in my opinion). Hopefully they will be able to unpack them as they get more satellites in the air with spot beams to give them the capacity they need now that they have to carry every tiny station in every local market that they cover.
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I would like to check out the Digital TV OTA signals just to see how their PQ is.
You can view OTA digital without buying a new TV. Get yourself a box like the Samsung 151 for OTA only. The boxes have NTSC output and the local digital channels will look awesome. Now if you do buy a digital set, prepare for your jaw to hit the floor.
Hey, thanks for the replies everyone. :D

I have seen HDTV at CC. There is still a puddle of my drool in front of a particual sony that I've been "checkin out".

Thanks for clearing up the DTV vs E* DBS signal. I was suspect that this was the case. I'll make sure to put an ant up in the attic when the time comes.

"My question is, am I already receiving DTV by using the DBS?"

Yes, DBS is digital TV. However, it is not an ATSC signal, it is MPEG-2 DVB (much like terrestrial digital in the UK, except with different security and different encoding so it can be used on the satellite)
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