frequency lists

Archived from groups: alt.satellite.tv,alt.satellite.tv.europe (More info?)

I have a satellite frequency list here, but I'm puzzled about one aspect:
For example, when I look under Astra 2 (28.2E), at some
frequencies/parameters I see multiple stations.

For freq. 10847 V I have the following stations:

BBC 8
BBC 9
BBC 10
BBC One Islands
BBC One Cambridge

Do they all use the same frequencies/parameters simultaneously? How can I
distinguish one from the other?




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ICQ 326628

Archived from groups: alt.satellite.tv,alt.satellite.tv.europe (More info?)

On Wed, 21 Jul 2004 22:43:39 +0200, "Linea Recta" <mccm.vos@abc.net>
wrote:

>I have a satellite frequency list here, but I'm puzzled about one aspect:
>For example, when I look under Astra 2 (28.2E), at some
>frequencies/parameters I see multiple stations.
>
>For freq. 10847 V I have the following stations:
>
>BBC 8
>BBC 9
>BBC 10
>BBC One Islands
>BBC One Cambridge
>
>Do they all use the same frequencies/parameters simultaneously? How can I
>distinguish one from the other?

Well you have to laugh. :-]

Anyway, an explanation...

Each station's video and audio is turned into a digital form. Since
this is nothing more than 1s and 0s, then so can all this data be
combined into the one package.

Think of it like with a compressed ZIP file. As once you open this
single file, then so do you often discover many other files hidden
within it.

Digital TV works nearly the same way. When all these stations are
transmitted through the one transponder.

The obvious next question is how can multiple digital stations, with
often better picture and sound quality, be sent in the same space that
used to house just one analogue station.

And the answer here is that they are indeed compressed. When this is
one useful thing that you can do with digital data. As if say the
background is all black, then so can the compression system just say
that there is x amount of black following.

In most cases the available bandwidth from a transponder is divided
between the number of stations using it. And the greater the
bandwidth, the better the picture quality.

Sky's system is a bit different, when it shares available bandwidth
between the stations in a better way. As when one station needs less
bandwidth, due to say the scene turning black, then so can this spare
bandwidth be allocated out to the other stations to use.

In the early days of digital they used to just reencode the very same
analogue broadcasts. These days they are more processed in digital
down the entire line.

One interesting thing to note is that the current MPeg compression
system used is an older and not very good one. As when broadcasters
switch to using MPeg4, which will certainly require new receivers,
then the number of stations on each transponder should about double.

Better yet they could use this extra space for HDTV broadcasts.

Since broadcasters can now share transponders, then so has this
expensive overhead been reduced to about 1/8th. That explains why
there are now a lot more stations around these days.

Reducing this is about 1/16th under MPeg4 would have equally large
advantages.

Cardman
http://www.cardman.com
http://www.cardman.co.uk

Archived from groups: alt.satellite.tv,alt.satellite.tv.europe (More info?)

"Andy Luckman (AJL Electronics)" <me8@privacy.net> wrote in message
news:ant2307360b0dVpW@office.ajlelectronics.co.uk...
> In article <2m9v0oFl03u9U1@uni-berlin.de>, Dave
> <URL:mailto:myozone@hotmail.com> wrote:
>
> > Fog and mirrors !
>
> What is?
>
> > try 1,0 's digital !!!
>
> ??
>
> Try this, it might help a lot:
>
> http://www.allmyfaqs.com/faq.pl?How_to_post
>
>
>

Well what was posted made sense to me!!


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