Yes - from a D book The receiver should be capable of demodulating all non-hierarchical modes specified in the
DVB-T Specification EN 300 744 [6]. It is not necessary for the receiver to demodulate
the hierarchical modes, but the presence of such a mode should not cause the receiver to
malfunction.

It should be, the different FEC (Forward Error Correction) rates are all in the original DVB-T specification. Of course, some equipment had problems with 16QAM 3/4 when that was introduced, and some with a mix of 2K and 8K carriers across the tuned multiplexes. (Some don't work with 8K carriers at all, but that's usually due to skimping on memory for the first-stage digital signal processor, in early boxes - more carriers requires more memory.)

The purpose of the trials at Caldbeck and Preseli would have been to reveal any equipment that wasn't compatible, though it would have been tested on the DTG's collection of equipment first.

If this is not a mistake then the MUXes must have a different number of channels across the country - which is not a tenable situation.

The only alternative is that the extra bandwidth will be used to increase the bit-rate of the LCNs in the MUXes for transmitters that can bear the loss of margin ?

We are already in the position where some post DSO areas have some muxes in the pre-DSO configuration. Also there are the differences between the nations.

So there is a precedent.

My own thought is that we only have partial information so far, which may contain errors. I think the situation should be clearer, shortly.

Hmm, Something odd is going on...

Waltham - 25 Oct (Please tell me I haven't got to retune the Hummy again?!),Only Arq B sees a mode change
Sutton - 1 Nov, Only Arq B sees a mode change
Nottingham - 20 Oct - Predicted worse coverage of Arq A, but Arq B unchanged. Only Arq B sees a mode change
Belmont - 18 Nov - Sees Arq A and Arq B become available for the first time (with better predictions than SDN) - both Arq A and Arq B at 3/4, Arq A then switches to 2/3 on 23 Nov.

According to Digital UK:-

A) New DSO events from ~Nov 2011 onwards resulting in COM muxes at full power switch to 64QAM 8k 3/4FEC 1/32GI MAINLY ON ALL 3 COM MUXES;

B) Some existing post DSO COM muxes running at full power have switched to 64QAM 8k 3/4FEC 1/32GI MAINLY ON ARQ B ONLY;

C) Some existing post DSO COM muxes running at full power WILL switch to 64QAM 8k 3/4FEC 1/32GI from ~Nov 2011 MAINLY ON ARQ B ONLY;

D) the rest are in a DUK mess, especially where some COM muxes are still on 16QAM post DSO.

I think DUK have got a fair few corrections to make & Ofcon needs to make an announcement.

I've put a preliminary version of the timetable on my website.

It appears that they will get the Arq B FEC change all up to date by 23/11/11 with the Tacolneston DSO (except for future DSOs). I think that Arqiva must have got a reason for doing all this work. They must have sold some more streams.

Arq A is better off than SDN, but lots of work to do.

SDN won't get any benefit until May/June 2012 because of Sandy Heath & Sudbury late retunes.

Sorry but this has lost me completely.

I suppose the most important aspect most people (including me) want to know is will these changes require yet more STB retunes?

No retunes, but as I understand it, if you are in a fringe reception areas and your reception of those COM muxes is marginal, they will become even more marginal after this change (and in some cases you might even lose them).

I think that's going to depend on your box. Some will just accept a change to the error correction method with no further changes, others will require a retune.

The error correction method is signalled on the Transmission Parameter Signalling carriers - 68 out of the 6,817 carriers making up the signal - which use a fixed, robust transmission and error correction method (far stronger than the actual data making up picture and sound) and repeats every 62 milliseconds. The information is there for the box to pick up on, but some seem to only read that information when specifically told to rescan, rather than continuously or when you change channels.

As others have said, the mode has been trialled at a couple of sites before the wider roll-out, so I'd imagine that switching between modes was included in that. Given the near-complete absence of any information about it, my guess is that those tests were successful.

If you're relatively new to digital TV reception, you may not know that this problem was faced in 2002/3 after ITV Digital failed. To improve coverage without increasing power or reducing interference, the ITC recommended and the new bidders all specified a change from 64QAM 2/3 to 16QAM 3/4 mode. The BBC's analysis of how receivers would behave can be found here. In the end, the winning bidders - the BBC and Crown Castle, which is now part of Arqiva - changed their multiplexes, 1, B, C and D to the more robust mode, while the losers - ITV, C4 running mux 2 and SDN running mux A - did not, as they would have had to close services. At switchover, everything went back to 64QAM 2/3 (except for the HD mux, which I won't go into as this is long enough already!)

Can someone put up a link to this information please.

Edit:

Ok got it, replace the Xs with your postcode
http://www.digitaluk.co.uk/postcodec...trade/XXXX+XXX

That is the only source.

Wonder if the BBC might want to try this out on BBCA in Scotland, so they can get both BBC Alba and the radio stations on at the same time

I'm sure that BBC A & D3&4 will be keen to get more capacity asap assuming the COM muxes have no problems.

Bristol Kings Weston & Nottingham should have had their Arq B muxes converted to the new error rate today and so should have a lot more null packets. Anyone notice any change?

DigitalUK have now decided that Rowridge is my most likely transmitter after always saying it was Mendip.

Mendip still showing 2/3 permanently on SDN and ARQ A.

Hmm, my Hummy can see a signal at 10% quality - it's not managed to detect a single Nottingham multiplex before now, I thought it was supposed to be worse

Maybe they turned the Fecking Knob the wrong way!.

They don't seem to have any Qualms about altering the setup to get more channels in.

So are we going to see some action at Stockland Hill, Black Hill, Pendle Forest, Sheffield and Waltham today?

Source: 10ash.info

Presumably this change in FEC requires a change in multiplex encoder at the Coding & Mux centre? So 2 versions of Arq B exist until Tacolneston DSO when all DSO'd transmitters get converted? At the transmitter they just have to select the new source, using the backup feed perhaps?

This would be a good thing IMO. From what I read, reception of the PSB muxes is laughably easy. Some people are receiving usable signals from four or even five regions, where previously they only received one or two watchable analogue regions through the same aerial.

Given this overkill situation, it makes sense to sacrifice robustness for capacity.

Shame it didn't happen at DSO. Are there really people who find the PSB signals only just good enough? Remember, the target is roof top aerials - if it doesn't work on your indoor aerial, it's down to you to replace it, not down to the broadcasters to sacrifice capacity to make your inadequate aerial work.

Cheers,
David.

Although isn't that more due to the use of wideband aerials rather than anything else, coupled with the allocation of mux frequencies?

And just because a few extra regions are received does not mean that they are of sufficient quality to be watchable 100% of the time.

What the aim should be is to make the intended region's SQ as high as possible, that way those that are in very local bad spots can get a reasonable signal (| wonder how many of those people reporting multiple regions are in areas of very good reception, and how many are in local dips, behind trees etc?)

TBH, I reckon most had no idea just how well the digital signals would be able to be received, so learning from their mistakes made when modelling ITV Digital, they played it safe rather than assuming the best-case scenario. If it turns out their playing it safe has led to much more coverage than anticipated, I think the FEC change is perfectly justified.

Multiple region reception is obviously going to be easier in those households that acquired high-gain kit pre-switchover, which to be honest is now overkill given the boosted signals. However, it still cannot be assumed that all households have that type of set-up.

With regards the FEC change, it will likely adversely affect those households just able to get a signal from a main transmitter instead of their local 3-mux relay, and with some of the key channels on the COM muxes not on Freesat, denies them of choice. But as was mentioned earlier in the thread, there will be some in urban areas where line of sight to the transmitter may not be possible, even on a roof-top aerial, and the changes could afFECt those households too, if not implemented correctly.

The allocation of PSB relay frequencies to co-channel with a COM mux frequency at its parent transmitter (as seen in my area) already causes the multiplex to be either wiped out, or receivable with low signal quality, despite high signal strength. The FEC change could wipe out more households' reception. This is especially annoying when pre-DSO the signal quality on the pre-DSO frequency was 9/10 and fell to 3/10 after DSO stage 2. It is very bad practice to give households access to services, and then take it away again. (It would be slightly different if you had reception, despite being outside of official coverage and then lost it.)

The only justifiable reason for a FEC change on BBC-A would be in Scotland due to BBC Alba and BBC National Radio. BBC red button services are reducing, therefore there is no need for additional capacity in the rest of the UK. However, due to the topography in Scotland, I would doubt that widespread multiple reception is possible, and that the extra robustness of the signal is very much welcome in rural areas, where some households may already have a large roof-top aerial.