Analogue Switch Off
Mark Carver
lecture given by an engineer from 'Digital UK [2]' on March 2nd 06,
regarding current plans and ideas for the coming switch over.
What follows is my understanding from listening to the talk, and
scribbling down facts and figures presented. Of course parts of the
plan will probably change and evolve in the coming months and years.
The following info and issues emerged:-
May 5th 2006 will be the date the national publicity campaign starts
in earnest.
Current estimates are there are 64 million TV sets in use in the UK.
Of these 25 million have some form of digital receiver (DTT, D-Sat,
D-Cab) attached. That leaves around 39-40m to 'convert', 62% of the total.
After analogue switch off at each transmitter, there will be six muxes.
PSB 1 (BBC)
PSB 2 (ITV/C4)
PSB 3 (BBC, C5 and S4C)
COM 1, 2 and 3 ('commercial' (non BBC,ITV/4/5) stations)
They will roughly equate to the six current muxes, the main exception
being that C5 and (in Wales) S4C will move into a shared PSB mux with
the Beeb.
All muxes will be 64QAM, initially at 2k. Once all UK transmitters are
converted, sometime during 2013, 8k working will be adopted.
All 1154 present analogue stations will carry PSB 1,2,3.
Not more than 200 will be permitted to carry COM 1,2, and/or 3, The
decisions for which stations do is entirely a matter for the
commercial channel operators. For frequency spectrum usage purposes
the number will be limited to 200 sites.
PSB muxes will be at ERPs typically 7dB less than analogue peak sync
COM muxes will be at ERPs typically 10dB less than analogue peak sync
There will be some exceptions however [1] see below.
Where possible all three PSB muxes will occupy existing analogue
allocations, which of course puts them 'in band' for any 'pre digital'
aerials (and communal distribution systems).
A month before analogue shut down day at a given site, BBC 2 analogue
and the present Mux 1 will cease. If the BBC 2 allocation is within
the new smaller UHF TV band (21-30/41-62) then overnight the old
allocation will carry PSB 1 at high power.
If BBC 2 falls outside the 'new' UHF TV band, then another analogue
channel will take its place for the remaining 4 weeks. That station's
old allocation takes PSB 1 instead.
For example, Crystal Palace BBC 2 is on UHF 33. That allocation is to
be 'sold off'. Therefore BBC 1 on Ch 26 might move to 33, and PSB 1
launch on Ch 26.
A month later BBC 1, ITV, C4 and if applicable, C5 will also shut
down, along with the low power DTT muxes 2,A,B,C,D replaced overnight
by PSB 2, 3, and COM 1,2,3 all at high power.
Most main transmitter sites will have fully redundant reserve DTT
aerials. As a result, and also because six high power services are to
be broadcast, significant mechanical, electrical, and RF
re-engineering will be required at most sites.
Most visibly at Black Hill and Caldbeck where new replacement masts
will be constructed. Wenvoe, Sandy Heath, and ISTR Divis will require
mechanical strengthening work. To this end, work on a temporary mast
begins at Wenvoe this autumn, to allow the existing mast to be
modified 'cold'. Work at Selkirk (the first Tx to be switched) starts
this summer to replace the antennas.
A frequency plan has been devised, but it needs ratifying. There's an
RCC conference in May 06, however only 112 of the UK's 1154 stations
will be considered. The remaining sites (most of which are <1kW) will
probably be subject to ad-hoc agreements between the UK and our
immediate RF neighbours, Eire, Netherlands, Belgium, France.
However because nothing is official, no frequency plan, or exact
switch-over dates can be confirmed yet. Where existing analogue
allocations are switched to DTT transmission, this is already agreed
and approved by the Chester 1997 conference.
The night each main station is switched over, all of its daughter
relays will be also. If BBC 2 at any of them fall in the 'to be sold'
allocations, the same scheme as mentioned above will be implemented.
[1] In order to maintain reception protection 99% of the time, some
transmitters might run at 4dB below current analogue levels.
A likely contender is Rowridge. It suffers during 'lift' conditions
interference from the continent. To assist viewers to enable more
robust reception two ideas are under consideration. One is to add a
vertical component to Rowridge's signal, the idea being that a VP
receiving aerial will discriminate better against distant interfering
HP transmissions.
The second is to have extra relays, at 'greenfield' sites working
possibly in SFNs. If the latter is adopted, then 8k working will be
needed in these areas ahead of a national switch.
Other south east sites are under consideration for a similar scheme,
notably Dover and Sudbury.
[2] http://www.digitaltelevision.gov.uk/
--
Mark
Please replace invalid and invalid with gmx and net to reply.
Scott
I may have missed something, but what is happening to the frequencies
from 31 to 40?
Scott
Mark Carver
> I may have missed something, but what is happening to the frequencies
> from 31 to 40?
They might be 'sold off' (along with 63 to 68) for other non broadcast
use.
dylan
"Mark Carver" <mark....@invalid.invalid> wrote in message
news:46t5piF...@individual.net...
> Scott wrote:
>
>> I may have missed something, but what is happening to the frequencies
>> from 31 to 40?
>
> They might be 'sold off' (along with 63 to 68) for other non broadcast
> use.
only 'non-broadcast' use ?
Colin
"dylan" <n...@nospam.com> wrote in message
news:dubo1g$83c$1...@newsg2.svr.pol.co.uk...
I thought that the usage was up to the purchaser, which meant that it could
be used for DVB-H or HDTV (assuming it was economical).
When Mark says 'non-broadcast use' I would have assumed he meant 'not for
the SDTV Digital TV services considered under the Digital Switchover plan'.
tim (in sweden)
"Mark Carver" <mark....@invalid.invalid> wrote in message
news:46t5piF...@individual.net...
>
>> I may have missed something, but what is happening to the frequencies
>> from 31 to 40?
>
> They might be 'sold off' (along with 63 to 68) for other non broadcast
> use.
And the government is keeping the money from the sale whilst
expecting the users of the middle channels to pay for freeing up
the space.
A bit like insisting the owner of a building pay to knock it down
and then keeping the proceeds from rebuilding to yourself.
tim
Scott
<mark....@invalid.invalid> wrote:
>Scott wrote:
>
>> I may have missed something, but what is happening to the frequencies
>> from 31 to 40?
>
>They might be 'sold off' (along with 63 to 68) for other non broadcast
>use.
I might still be missing something, but where will HDTV be going?
Mark Carver
>
> I thought that the usage was up to the purchaser, which meant that it could
> be used for DVB-H or HDTV (assuming it was economical).
>
> When Mark says 'non-broadcast use' I would have assumed he meant 'not for
> the SDTV Digital TV services considered under the Digital Switchover plan'.
Yes, correct. It's still open to *any* other use outside of that scope
(6 SD DTT muxes )
John Rumm
> I might still be missing something, but where will HDTV be going?
On digital sat.
--
Cheers,
John.
/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/
Bill Wright
"Mark Carver" <mark....@invalid.invalid> wrote in message
> As discussed recently in the 'Sandy Heath' thread, I attended a
> lecture given by an engineer from 'Digital UK [2]' on March 2nd 06,
> regarding current plans and ideas for the coming switch over.
>
> What follows is my understanding from listening to the talk, and
> scribbling down facts and figures presented.
Many thanks for this Mark.
Bill
Adrian
Satellite? There is no guarantee that HDTV will ever be broadcast
terrestrially, though it probably will be.
--
Adrian A
Dave Farrance
>What follows is my understanding from listening to the talk, and
>scribbling down facts and figures presented. Of course parts of the
>plan will probably change and evolve in the coming months and years.
Thanks. Very interesting.
>After analogue switch off at each transmitter, there will be six muxes.
>PSB 1 (BBC) PSB 2 (ITV/C4) PSB 3 (BBC, C5 and S4C)
>COM 1, 2 and 3 ('commercial' (non BBC,ITV/4/5) stations)
So the DTT UHF frequencies and mux groupings are going to be swapped
around in each region as the analogue switch-off happens. It's going to
be quite a job to keep the public and the aerial industry supplied with
understandable and correct information as that happens, but I
understand the necessity.
>All muxes will be 64QAM, initially at 2k. Once all UK transmitters are
>converted, sometime during 2013, 8k working will be adopted.
The only reason they'd want 8k is to introduce some
single-frequency-networks, so I guess that many of the UHF frequencies
would change *again* when that happens.
>All 1154 present analogue stations will carry PSB 1,2,3.
>Not more than 200 will be permitted to carry COM 1,2, and/or 3 ...
Fair enough. I bet that the people in the regions served by the small
relays will be upset by this, though.
>PSB muxes will be at ERPs typically 7dB less than analogue peak sync
>COM muxes will be at ERPs typically 10dB less than analogue peak sync
In practice, I believe 7dB less than analogue means a substantial
*increase* in coverage compared to analogue.
>The second is to have extra relays, at 'greenfield' sites working
>possibly in SFNs. If the latter is adopted, then 8k working will be
>needed in these areas ahead of a national switch.
To get an SFN working, in addition to switching to 8K, the
guard-interval needs to be raised above it's current level. This means
that there'll be less bandwidth at those sites. I wonder if they've
taken into account how they're going to integrate this with the
national distribution of the muxes.
> http://www.digitaltelevision.gov.uk/
The leaflet seems to be as clearly written with plain English as it can
be, but it's still going to be one of the most technical and complex
leaflets that ever popped through the nation's letterboxes. The
technically disinclined are going to be in trouble with this.
--
Dave Farrance
Andy Wade
> When Mark says 'non-broadcast use' I would have assumed he meant 'not for
> the SDTV Digital TV services considered under the Digital Switchover plan'.
Exactly so. It is hoped by broadcasters that at least some of the
so-called 'released' channels can be used for new broadcast services,
such as HD and DVB-H.
Also of notable interest is that DVB are starting work on a DVB-T2
standard (c.f. DVB-S2) which could rectify some of the mistakes made in
DVB-T - mainly the lack of a long time-interleave - and extend the
standard to include new modulation and coding techniques (turbo-codes,
improved source codecs, MIMO, etc.). Interesting times may be ahead.
--
Andy
Matti Lamprhey
> Scott wrote:
> >
> > [...] where will HDTV be going?
>
> Satellite? There is no guarantee that HDTV will ever be broadcast
> terrestrially, though it probably will be.
I'm willing to bet that there will be no terrestrial broadcasting in 25
years' time; it will all be satellite, augmented by local cable where
dishes are a problem.
Matti
charles
I won't take you up. I might not be around in 25 years time to collect my
winnings ;-)
--
From KT24 - in "leafy" Surrey
Using a RISC OS5 computer
Scott
<DaveFa...@OMiTTHiSyahooANDTHiS.co.uk> wrote:
>Mark Carver <mark....@invalid.invalid> wrote:
>
>>What follows is my understanding from listening to the talk, and
>>scribbling down facts and figures presented. Of course parts of the
>>plan will probably change and evolve in the coming months and years.
>
>Thanks. Very interesting.
>
>>After analogue switch off at each transmitter, there will be six muxes.
>>PSB 1 (BBC) PSB 2 (ITV/C4) PSB 3 (BBC, C5 and S4C)
>>COM 1, 2 and 3 ('commercial' (non BBC,ITV/4/5) stations)
>
>So the DTT UHF frequencies and mux groupings are going to be swapped
>around in each region as the analogue switch-off happens. It's going to
>be quite a job to keep the public and the aerial industry supplied with
>understandable and correct information as that happens, but I
>understand the necessity.
>
>>All muxes will be 64QAM, initially at 2k. Once all UK transmitters are
>>converted, sometime during 2013, 8k working will be adopted.
>
>The only reason they'd want 8k is to introduce some
>single-frequency-networks, so I guess that many of the UHF frequencies
>would change *again* when that happens.
>
I assumed all the relays would be a SFN with the main tranmitter. Is
this impossible because the relays receive their signal from the main
transmitter in the first place? Just asking.
Scott
Mark Carver
>>The only reason they'd want 8k is to introduce some
>>single-frequency-networks, so I guess that many of the UHF frequencies
>>would change *again* when that happens.
>>
>
> I assumed all the relays would be a SFN with the main tranmitter. Is
> this impossible because the relays receive their signal from the main
> transmitter in the first place? Just asking.
Yes, the plan is for most relays to continue to receive their feeds by
off air reception.
Dickie mint
> <snip>
> After analogue switch off at each transmitter, there will be six muxes.
>
> PSB 1 (BBC)
> They will roughly equate to the six current muxes, ...........
>
> All 1154 present analogue stations will carry PSB 1,2,3.
> A month before analogue shut down day at a given site, BBC 2 analogue
> and the present Mux 1 will cease. If the BBC 2 allocation is within
> the new smaller UHF TV band (21-30/41-62) then overnight the old
> allocation will carry PSB 1 at high power.
>
> If BBC 2 falls outside the 'new' UHF TV band, then another analogue
> channel will take its place for the remaining 4 weeks. That station's
> old allocation takes PSB 1 instead.
>
> For example, Crystal Palace BBC 2 is on UHF 33. That allocation is to
> be 'sold off'. Therefore BBC 1 on Ch 26 might move to 33, and PSB 1
> launch on Ch 26.
>
> A month later BBC 1, ITV, C4 and if applicable, C5 will also shut
> down, along with the low power DTT muxes 2,A,B,C,D replaced overnight
> by PSB 2, 3, and COM 1,2,3 all at high power.
>
>
For English Regions was there any indication of whether PSB1 will be Mux
1 rehashed in the region?
Although by 2012 the ER kit will be so old and rickety it'll have been
replaced! Methinks centralised playout will happen before this all
starts. Oops, 2008 isn't it? Bit too late to get a scheme in for then !
Mark Carver
> Mark Carver wrote:
> For English Regions was there any indication of whether PSB1 will be Mux
> 1 rehashed in the region?
No, that was beyond the scope of the talk, and the influence of
'Digital UK'. They are only concerned with RF planning matters.
Scott
<mark....@invalid.invalid> wrote:
>Scott wrote:
>
>>>The only reason they'd want 8k is to introduce some
>>>single-frequency-networks, so I guess that many of the UHF frequencies
>>>would change *again* when that happens.
>>>
>>
>> I assumed all the relays would be a SFN with the main tranmitter. Is
>> this impossible because the relays receive their signal from the main
>> transmitter in the first place? Just asking.
>
>Yes, the plan is for most relays to continue to receive their feeds by
>off air reception.
Why can't they use satellite? And why can't they all share the same
frequency if they are in the same TV region?
Scott
Mark Carver
> On Sat, 04 Mar 2006 15:11:45 +0000, Mark Carver
> <mark....@invalid.invalid> wrote:
>
>
>>Scott wrote:
>>
>>
>>>>The only reason they'd want 8k is to introduce some
>>>>single-frequency-networks, so I guess that many of the UHF frequencies
>>>>would change *again* when that happens.
>>>>
>>>
>>>I assumed all the relays would be a SFN with the main tranmitter. Is
>>>this impossible because the relays receive their signal from the main
>>>transmitter in the first place? Just asking.
>>
>>Yes, the plan is for most relays to continue to receive their feeds by
>>off air reception.
>
>
> Why can't they use satellite?
Many relay sites are simply a wooden pole, with a telephone box sized
hut attached, having a 1+ metre dish added would cause planning
permission problems in many cases, and would need to be 'secure' from
vandals etc. That would require security fences, and therefore more
land. You need a large dish, because unlike DTH satellites such as
Astra 2, the transmit powers of distribution birds is much lower.
Have a look at the shot at the bottom of this page:-
http://tx.mb21.co.uk/gallery/angus.asp
> And why can't they all share the same
> frequency if they are in the same TV region?
That was brought up during the Q+A session. Because there are
something like 29 TV regions, and not all BBC/ITV ones are an exact
match, SFNs on a regional basis would consume just as many frequencies
as not using them, it was claimed.
davidr...@postmaster.co.uk
[snip]
Many thanks for your report Mark!
> Scott wrote:
> > And why can't they all share the same
> > frequency if they are in the same TV region?
>
> That was brought up during the Q+A session. Because there are
> something like 29 TV regions, and not all BBC/ITV ones are an exact
> match, SFNs on a regional basis would consume just as many frequencies
> as not using them, it was claimed.
I think it's more because they don't want to change the way TV is
distributed, and they are trying to keep signals "in group" as much as
possible.
The "too many frequencies" argument is just rubbish:
BBC One is the only regionalised BBC service on DTT.
ITV1 is regionalised (though it's mainly just the adverts now).
CH4 and five carry regionalised adverts IIRC.
S4C and BBC 2W are available in Wales only.
The other channels aren't regionalised at all.
So put the regional channels in one mux. Then the other 5 muxes can
operate as national SFNs - 5 muxes = 5 RF channels = lots of space!
That would dramatically reduce the number of channels required, and
make all 6 muxes available from every tx site - no "second class"
Freeview homes.
The problem is that channels in a national SFN would be out of group
for most viewer's aerials, and it would make traditional "relay"
stations almost impossible to run - requiring a dedicated (i.e. not off
air) feed to each.
It's for this reason that we're keeping relays as relays, avoiding SFNs
in most places, and preventing anyone on a relay from receiving half of
the Freeview service.
Maybe there will be technological advances, or economical realities, pr
political pressure, or something, which mean some of the commercial
muxes will make it onto relays as part of an SFN - I can't see that
anyone can stop them from using more than 200 sites if the extra sites
don't use any "new" frequencies.
btw, 8k is more robust to impulsive interference, so it makes sense to
switch to 8k even without SFNs.
Cheers,
David.
Peter Duncanson
<davidr...@postmaster.co.uk> wrote:
>BBC One is the only regionalised BBC service on DTT.
BBC Two is regionalised into the four national regions: England, Wales,
Scotland, and Northern Ireland.
--
Peter Duncanson
UK
Andy Wade
> So put the regional channels in one mux. Then the other 5 muxes can
> operate as national SFNs
As well as the other issues mentioned that would require an increase in
the guard interval fraction, thus reducing the net capacity. With the
current GI fraction of 1/32 and 8K modulation the GI will only be 28 us
(8.4 km) - nowhere near enough for a national network.
--
Andy
Peter Hayes
As they do in Spain.
--
Peter