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SAT-Usenet 2/96

SAT-Usenet 
2/96
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Deadline for this issue: 25.07.96 12:10

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Today Issue of SAT-Usenet is entirely dedicated to digital television. A well
known guy in the Internet ("Markus") got himself a digital receiver from
PACE, and some trouble with it. May be some of our readers have the same
problems. I would save this tips for the time you get your own digital
receiver folks.
The Editor.

>I have just received a new DVB digital TV receiver, which I would like
>to test. A DVB receiver has to be tuned into a "home channel" during
>first installation, where it will find its first DVB data signal and
>from that it can extract the broadcasted frequency list of all other
>transponders and programs.

Just send it to me Markus. I'll get it to work and send it back - say in
6 months or so :-)

Seriously the answer is to get a copy of TELE-satellit and check out the
digital television frequencies/FECs etc or take the easy way out and
browse the TS web site (www.tele-satellit.com) and send a Q to drdish@tv.
He has a lot of experience getting digital RXs from around the world to
work in Europe.

Dee

-------------------
For those who just entered the thread: Markus has a Pace DVB receiver
and wants to receive an Astra signal with an old 10 GHz LNB. He says that
he is on ASTRA 1E's transponder 71 and gets the network name "Astra".

First question: Did you manage to tell the box the actual LOF of your LNB?

Maybe you're on some different transponder with only basic SI on it? But I
have to say, the only DVB-SI that, from my point of view, is
physically needed is the network information table, which gives you the
transponder frequencies. The rest is describing services and events and
is not exactly needed for decoding. The demux information is specified
in the MPEG-2 transport stream syntax.

For the moment, let's take it for given that you are actually on txp 71.
Here you should be able to pick up ARD and ZDF. MTV and VH-1 have left this
transponder a few weeks ago.

You say that your receiver is rather old (which means just half a year these
days). In this case you might have the following problem:

In the MPEG-2 standard a video_sequence begins with a video_sequence_header.
This header may start at the beginning of a byte (bytealigned) or not. The
video decoder chip in the pace box is a STi 3500 from SGS Thomson, the same
as is used in the RCA box for DirecTV. I have been told that the Thomson
chip can only handle bytealigned headers. Thus a non-aligned sequence cannot
be decoded.

Furthermore, we had some of the Pace boxes in my company last year in summer
and I have learnt that they were unable to decode MPEG-2 B-frames due to
memory constraints (a B-frame is a bidirectionally encoded picture, i.e. the
decoder resembles the picture by interpolating between a foregoing and a
following picture, this requires up to 16 Mbit of DRAM). Maybe that's why the
screen is dark - then it will remain so :-(. We had no luck at all with these
boxes.

Concerning your LNB questions, I don't think that you're having trouble
because you're using an old LNB. The "fundamental" difference between an
"analog" and a "digital" LNB is the LOF (analog - 9,75 or 10 GHz, digital
10.6 GHz). I've never heard that the 22 kHz tone does any harm to LNBs,
but that might be my fault. I'm not quite sure on this, but I would rather
say there's no problem with that.

There was once a small discussion about LNB phase noise in this group. I had
said that we hadn't any problems with it. I have to add that this applies
only to wideband TDM signals. For SCPC signals with a small bandwidth (e.g.
8 MHz) phase noise IS a problem.
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