DSO question
 

On Thu, 20 Jan 2011 15:31:32 +0000, Bill Wright wrote:

Cxxxxxxxl.

:-) I'd have thought it normal to see Hxxxxxxxxxh and Bxxxxxx Lxxx
depending on whether you prefer S6 or S2, but why Cxxxxxxxl for S10?

--
Phil Cook

DSO question
 

"Bill Wright" wrote in message
...
Rick wrote:

I couldn't think of a single person using analogue, years before Mendip
went DSO.

I came across a bloke in a nice house with five of them living in it, and
they had analogue only, and the C5 was obliterated by the VCR RF output.
He was a total nutter though, and I think the kids were living for the day
when they could move out.


I've been out of the trade now for a number of years Bill, however I still
occasionally keep in touch with the local branch of one of the largest
aerial wholesalers in the country, apparently since DSO the aerial side of
things have died a death and according to friends in the business it's
mainly only the lower power COM muxes that still provide them with any
aerial work, that, retuning, extra outlets etc, however, without wishing to
sound too pessimistic, I reckon after mid 2012 even that work will
eventually taper off.
I'm still amazed by the coverage now the PSB multiplexes are on full power,
I pick up rock solid (BBC) reception on the side of a group C/D aerial from
a group A transmitter (Stockland Hill) located around 50 miles away, back in
the seventies with a masthead amplifier and the correct roof mounted aerial
I could receive just about watchable Westward ITV analogue, until they built
an office block in the town centre and it then became unwatchable, of course
it was much more exciting getting out of region ITV programmes back then;)

DSO question
 

On 20/01/2011 11:19, Mark Carver wrote:
.............
As far as relay stations are concerned, dual operation (analogue and
DTT) transposers are installed in the months leading up to DSO. On DSO
night it is more or less a flick of a switch at most of those, but of
course in some areas there are several dozen to visit overnight.

As I discovered, in helping someone on another forum, there is at least
one relay who's analogue and DTT frequencies are virtually the same.
Consequentially the DTT transmitters will not be switched on until
analogue is switched off. To compound the issue the Linnet Valley relay
is a fill-in for the west of Bury St. Edmunds where DTT is, currently,
impossible!

Richard

DSO question
 

On Thu, 20 Jan 2011 11:44:28 +0000, Mark Carver
wrote:

On 20/01/2011 11:29, Rick wrote:

I still find it puzzling why it takes this country a total of five years
to complete something that most other countries seem to accomplish
overnight.

We've got a very extensive UHF network, of 1154 transmitters, which
carried (before DSO started) 4 analogue services. The other extreme is
the Netherlands that has a total network of about 30 transmitters.

Not counting Luxy (overnight, 3tx?) or Liechtenstein then :-)

--
Old anti-spam address cmylod at despammed dot com appears broke
So back to cmylod at bigfoot dot com

DSO question
 

"Mark Carver" wrote in message
...
On 20/01/2011 10:13, Mark wrote:
Can anyone tell me *why* there is a two-week gap between phase
1 and
phase 2 of DSO? i.e. Why not do it all at the same time?

It's a good question. I've been told it's to allow for people
who, (for whatever reason) haven't equipped themselves with a
Freeview box in time, not to be left with nothing to watch.
They still have BBC 1, ITV, and C4 analogue for a fortnight,
while they sort themselves out. It also reduces the workload on
Arqiva with the amount of work they have to do overnight, it's
spread over two nights, 14 days apart.

Interestingly however, the Channel Islands were done in one big
step over night, and also interestingly there was no DTT
service at all there until DSO, so everybody who still wanted
terrestrial reception had to buy a box. I suspect because the
CI didn't have Freeview until last year, use and penetration of
Sky and Freesat is much higher ?





The problems with the CIs was French TV. They had to wait until
channels were cleared.

As for the two weeks apart, yes it is to make sure people have
got digi boxes - if BBC2 (or in some cases ITV) disappears they
will sit up and take notice.

At DSO there is a lot of work to do on main stations and larger
relays. Doing one in advance does help with workload, but the
main reason is practicality. It allows one channel of analogue
kit to be removed (on the larger relays) so that the DTTV racks
can be put in their final resting places amongst other things. It
also gives time for the telemetry to be tested - the demands of
the broadcasters in terms of how quickly any station must notify
of a fault and how quickly Arqiva must respond are frightening.


--
Woody

harrogate three at ntlworld dot com

DSO question
 

"Mark Carver" wrote in message
...
On 20/01/2011 10:58, Mark wrote:
On Thu, 20 Jan 2011 10:37:23 +0000, Mark Carver

Judging from the amount of nagging that has been going on for
years I
would have thought that everyone who cares would have already
done
something about it well before switchover ;-)

Apparently some people, despite months of nagging, don't do
anything until the event has happened, (and then complain !)

It also
reduces the workload on Arqiva with the amount of work they
have to do
overnight, it's spread over two nights, 14 days apart.

Good point. I'm not sure how much work would be left to do
for the
actual switchover. Won't it be a matter of just flicking a
switch or
two?

No ! The old analogue transmitters are connected to the
transmission aerials with 6in feeders, that within the building
is more akin to plumbing. So to connect up the new high power
DTT transmitters there's a lot of mechanical work involved. Of
course a lot is prep'ed before hand, but even so there's an
hour or two of frantic effort to switch the feeders over.

You get some idea of what's involved from Stockland Hill's DSO
photos

http://tx.mb21.co.uk/gallery/stockla.../dso/index.php

As far as relay stations are concerned, dual operation
(analogue and DTT) transposers are installed in the months
leading up to DSO. On DSO night it is more or less a flick of a
switch at most of those, but of course in some areas there are
several dozen to visit overnight.

--

Well, nearly.

On the small relays a very clever transposer is used. If it picks
up analogue on a given channel it will transpose to a different
programmed channel and power.

When the analogue goes off it shuts down.

When the signal comes back in digital on the same or a different
pre-programmed channel the transposer comes back to life and
rebroadcasts at whatever power and on whatever channel is set in
digital. Unless a unit fails there is no need to visit the site
until the next day or two to take it off for a short time to do
the spectrum plots.


--
Woody

harrogate three at ntlworld dot com

DSO question
 

On Jan 20, 2:27*pm, Mark Carver wrote:
On 20/01/2011 11:59, Rick wrote:
although AIUI, by reading various newsgroups, digital (at least ATSC)
doesn't appear to work too well at lower VHF frequencies, does the same
apply to DVB-T?

I don't know, never played with VHF reception of DVB-T. A colleague of
mine has though, no particular problem, and you can get away with using
'rabbit ears' he told me :-)
--
Mark

The US is also using ATSC around and above our
VHF band I frequencies (54 -89 MHz). Reflections incl
sporadic E layer, man made noise, very large yet low gain
aerials - it is difficult and ATSC is even more than
DVB-T based on an (mostly wrong) AGWN assumption. :(
(ATSC is very outdated).

The VHF channels allocated for DTT in ITU regiaon 1 in
Geneva 2006 are all in VHF band III 174-230 MHz (Ch 5-12).

DTT in VHF Band III works nicely in Finland, Sweden
and Germany. It is also used in Italy.
The main problem with DTT in VHF band III is the need
for an extra VHF aerial. This is one reason Germany is
moving avay from DTT in band III, I guess the DAB lobby
was also against´DTT using VHF,

Sweden could not get more UHF channels in its border areas
so in order to enable a 7th mux, they uses UHF inland
and in the north, while VHF band III is used near Norway,
Denmark, Germany, Poland and the Baltic contries.

60 % of all households do not need a VHF aerial and only
40 % of households will need a VHF aerial.

Lars :)

DSO question
 

On Jan 20, 4:04*pm, Mark Carver wrote:
On 20/01/2011 14:29, Mark wrote:

Thanks for the post. *I don't quite understand why new aeriels are
required though.

You can get some very high voltages produced with the sort of power
levels 6 x COFDM DTT muxes produce, far higher AIUI than 4 x analogue
transmissions, despite the peak power levels for analogue being higher
than the mean power for DTT, so new aerials are required.

The Peak to Average Power Ratio - PAPR - is one of the bigger
problems with COFDM signals forcing bigger TX power amps to
maintain linear amplification. A bigger amps is much less efficient.

But I am a bit surprised that this is a TX antenna problem too?

DVB-T2 has the option to not use a few af the carriers for data,
but modulate these few carriers with a signal that can reduce the
powerpeak. (this is called tone reservation)
It is , however, not used in the UK - AFAIK.

Also some of the analogue aerial stacks are over 40 years old.

No arguments here.

I guess directional changes in the TX antennas has forced some
changes ?
and several antennas are moving from grouped to wideband!

Lars :)

DSO question
 

Rick wrote:

"Bill Wright" wrote in message
...
Rick wrote:

I couldn't think of a single person using analogue, years before
Mendip went DSO.

I came across a bloke in a nice house with five of them living in it,
and they had analogue only, and the C5 was obliterated by the VCR RF
output. He was a total nutter though, and I think the kids were living
for the day when they could move out.


I've been out of the trade now for a number of years Bill, however I
still occasionally keep in touch with the local branch of one of the
largest aerial wholesalers in the country, apparently since DSO the
aerial side of things have died a death and according to friends in the
business it's mainly only the lower power COM muxes that still provide
them with any aerial work, that, retuning, extra outlets etc, however,
without wishing to sound too pessimistic, I reckon after mid 2012 even
that work will eventually taper off.
I'm still amazed by the coverage now the PSB multiplexes are on full
power, I pick up rock solid (BBC) reception on the side of a group C/D
aerial from a group A transmitter (Stockland Hill) located around 50
miles away, back in the seventies with a masthead amplifier and the
correct roof mounted aerial I could receive just about watchable
Westward ITV analogue, until they built an office block in the town
centre and it then became unwatchable, of course it was much more
exciting getting out of region ITV programmes back then;)

Yes, I think the power of the post DSO-transmitters is far too high.
Apart from CCI issues I can receive Winter Hill here, yet in the
analogue days it was a barely discernible signal.

Bill

DSO question
 

On Thu, 20 Jan 2011 14:29:18 +0000, Mark
wrote:

On Thu, 20 Jan 2011 11:19:29 +0000, Mark Carver
wrote:

On 20/01/2011 10:58, Mark wrote:
On Thu, 20 Jan 2011 10:37:23 +0000, Mark Carver

Judging from the amount of nagging that has been going on for years I
would have thought that everyone who cares would have already done
something about it well before switchover ;-)

Apparently some people, despite months of nagging, don't do anything
until the event has happened, (and then complain !)

It also
reduces the workload on Arqiva with the amount of work they have to do
overnight, it's spread over two nights, 14 days apart.

Good point. I'm not sure how much work would be left to do for the
actual switchover. Won't it be a matter of just flicking a switch or
two?

No ! The old analogue transmitters are connected to the transmission
aerials with 6in feeders, that within the building is more akin to
plumbing. So to connect up the new high power DTT transmitters there's a
lot of mechanical work involved. Of course a lot is prep'ed before hand,
but even so there's an hour or two of frantic effort to switch the
feeders over.

You get some idea of what's involved from Stockland Hill's DSO photos

http://tx.mb21.co.uk/gallery/stockla.../dso/index.php

As far as relay stations are concerned, dual operation (analogue and
DTT) transposers are installed in the months leading up to DSO. On DSO
night it is more or less a flick of a switch at most of those, but of
course in some areas there are several dozen to visit overnight.

Thanks for the post. I don't quite understand why new aeriels are
required though.

A digital TV needs a digital aerial. We have discussed this
previously :-)