Hi,

I've just put up a new page that people may find an interesting read, It
outlines the history of the use of PCM and NICAM by the BBC to distribute
their radio networks. You can find the page at

http://www.audiomisc.co.uk/BBC/PCMandNICAM/History.html

My thanks to the many excellent ex-BBC engineers who have helped and
advised.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

In article ,
Jim Lesurf wrote:
Hi,

I've just put up a new page that people may find an interesting read, It
outlines the history of the use of PCM and NICAM by the BBC to distribute
their radio networks. You can find the page at

http://www.audiomisc.co.uk/BBC/PCMandNICAM/History.html

My thanks to the many excellent ex-BBC engineers who have helped and
advised.


an excellent document. I've possibly got the odd quibble, but nothing to
worry about.

--
From KT24

Using a RISC OS computer running v5.16

In article , charles
wrote:
In article , Jim Lesurf
wrote:
Hi,

I've just put up a new page that people may find an interesting read,
It outlines the history of the use of PCM and NICAM by the BBC to
distribute their radio networks. You can find the page at

http://www.audiomisc.co.uk/BBC/PCMandNICAM/History.html

My thanks to the many excellent ex-BBC engineers who have helped and
advised.


an excellent document. I've possibly got the odd quibble, but nothing to
worry about.

During the production process (a better description that saying I 'wrote'
it) I decided that the best I could hope for was to get a sort of 'least
squares fit minimum value' from all the comments from about a dozen
engineers who had various quibbles. :-)

I do plan that various subtopics will be dealt with in future by other
pages that go into more depth and expose some of the details that I had to
gloss over and simplify to get such a short description and have it
readable by non-engineers. The detailed pages will also let those involved
give more direct comments and their POV, etc.

I regard the page I've done as a sort of potted overview that reminds
people of a number of historic/significant/fascinating events, etc. But
also as a central point around which more could be built.

For now, though, I'm going on to 'something completely different' for a
while and let my head clear of things like EDI and equipment code numbers,
and details of the bits! There is still a lot to find out.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

In article ,
Jim Lesurf wrote:
Hi,

I've just put up a new page that people may find an interesting read, It
outlines the history of the use of PCM and NICAM by the BBC to distribute
their radio networks. You can find the page at

http://www.audiomisc.co.uk/BBC/PCMandNICAM/History.html

My thanks to the many excellent ex-BBC engineers who have helped and
advised.

Excellent article, Jim. Just as I (no longer) remember it. ;-)

Would you check the end of the second paragraph from the top?

--
*I'll try being nicer if you'll try being smarter

Dave Plowman London SW
To e-mail, change noise into sound.

On 24/11/2011 17:13, Jim Lesurf wrote:
Hi,

I've just put up a new page that people may find an interesting read, It
outlines the history of the use of PCM and NICAM by the BBC to distribute
their radio networks. You can find the page at

http://www.audiomisc.co.uk/BBC/PCMandNICAM/History.html

My thanks to the many excellent ex-BBC engineers who have helped and
advised.

Nice stuff Jim, copied to uk.tech.broadcast


--
Mark
Please replace invalid and invalid with gmx and net to reply.

www.paras.org.uk

On Thu, 24 Nov 2011 22:31:37 +0000, Mark Carver
wrote:

On 24/11/2011 17:13, Jim Lesurf wrote:
Hi,

I've just put up a new page that people may find an interesting read, It
outlines the history of the use of PCM and NICAM by the BBC to distribute
their radio networks. You can find the page at

http://www.audiomisc.co.uk/BBC/PCMandNICAM/History.html

My thanks to the many excellent ex-BBC engineers who have helped and
advised.

Nice stuff Jim, copied to uk.tech.broadcast

You look like you could answer this:

In a communal antenna system what optimum signal level would you
target for digital terrestrial TV? And is there an industry standard
for minimum acceptable level?

d

"Jim Lesurf" wrote in message
...
Hi,

I've just put up a new page that people may find an interesting read, It
outlines the history of the use of PCM and NICAM by the BBC to distribute
their radio networks. You can find the page at

http://www.audiomisc.co.uk/BBC/PCMandNICAM/History.html

My thanks to the many excellent ex-BBC engineers who have helped and
advised.

Interesting stuff. You mentioned that much of the reason for using PCM was
the poor quality of long-distance analogue music circuits. But it's worth
pointing out that the GPO was trying to phase out analogue music circuits at
that time because they were a nuisance to the GPO which was then in the
process of converting its junction and trunk network from baseband audio and
FDM to PCM. So the parallel conversion of BBC circuits to PCM dovetailed in
nicely with what the GPO/BT was doing. Of course telephone PCM was of rather
lower quality than the BBC's. It used an 8kHz sampling rate and non-linear
quantisation steps (known as A-law) to give 12-bit resolution for low levels
signals but increasingly lower resolution at higher signal levels; overall
bit rate being 64kb/s. 30 such circuits (plus 2 signalling channels, giving
an overall bit rate of 2048kb/s) formed the basic level multiplex and were
used to replace baseband audio on twisted-pair junction circuits giving a
15-fold increase in traffic capacity for a much lower cost than having to
install additional line-plant. Several of these basic-level multiplexes
would then be multiplexed together to form higher level multiplexes
replacing FDM on long-distance trunk co-ax cable routes. My understanding is
that the BBC designed their equipment so that their digital bit-streams
could directly replace that from an integral number of 2048kb/s telephone
systems on such trunk circuits.

David.

On 24/11/2011 23:12, David Looser wrote:

advised.

Interesting stuff. You mentioned that much of the reason for using PCM was
the poor quality of long-distance analogue music circuits. But it's worth
pointing out that the GPO was trying to phase out analogue music circuits at
that time because they were a nuisance to the GPO which was then in the
process of converting its junction and trunk network from baseband audio and
FDM to PCM. So the parallel conversion of BBC circuits to PCM dovetailed in
nicely with what the GPO/BT was doing. Of course telephone PCM was of rather
lower quality than the BBC's. It used an 8kHz sampling rate and non-linear
quantisation steps (known as A-law) to give 12-bit resolution for low levels
signals but increasingly lower resolution at higher signal levels; overall
bit rate being 64kb/s. 30 such circuits (plus 2 signalling channels, giving
an overall bit rate of 2048kb/s) formed the basic level multiplex and were
used to replace baseband audio on twisted-pair junction circuits giving a
15-fold increase in traffic capacity for a much lower cost than having to
install additional line-plant. Several of these basic-level multiplexes
would then be multiplexed together to form higher level multiplexes
replacing FDM on long-distance trunk co-ax cable routes. My understanding is
that the BBC designed their equipment so that their digital bit-streams
could directly replace that from an integral number of 2048kb/s telephone
systems on such trunk circuits.

Dave's been cutting and pasting from google searches again.
--

Jim Lesurf wrote...

It
outlines the history of the use of PCM and NICAM by the BBC to distribute
their radio networks. You can find the page at

http://www.audiomisc.co.uk/BBC/PCMandNICAM/History.html

An excellent and illuminating article Jim.
I like your writing style, engaging and authoritative but not overly
formal .

--
Ken O'Meara
http://www.btinternet.com/~unsteadyken/

"dave" wrote in message
o.uk...
On 24/11/2011 23:12, David Looser wrote:

advised.


Dave's been cutting and pasting from google searches again.
--

Who's "Dave"? you?

David.