All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
s hugh-jones: I suggest you do a full retune.
It's possible that changes have been made to the Packet Identifiers (PIDs) which tell the box which bits of the transmitted data-stream contain the sound and teletext data. The video and audio, and subtitles, are carried in separate datastreams, so the first stage of decoding has to know which one contains what information for which service.
Boxes are supposed to check the Program Map Table every time, so they pick up the associations properly even if the broadcasters have changed something. Yours may not be doing this and may be expecting to find the audio and teletext data at an old location. As I said, retuning should fix this problem.
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Richard: You can probably get a list of major holdings via Companies House as I believe they are required to report. Go to WebCHeck - Select and Access Company Information and search for British Sky Broadcasting.
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Steve Williams: I assume they wanted to reduce the volume of support calls! The UK is unusual in that there is still such a high proportion of terrestrial viewing, most other countries which cut-over in a short period have far fewer terrestrial viewers.
I think it's down to a combination of the strength of the BBC, the fact that all channels could be received from the same transmitter using the same aerial, a blanket television transmission network covering a very large part of the population, and the early provision of a Digital Terrestrial Television system (even if the pay-part collapsed, at least it did so quickly). Cable systems weren't allowed to carry other channels until 1984, when the relay transmitter network was mostly complete. For these reasons, cable never had the take-up in the UK that it has done overseas.
At the start of 2006, which is roughly when the phased rollout plan was committed to, 53.8% of viewing on primary sets was terrestrial (analogue or digital), while it was 77.7% on secondary sets. That's a heck of a lot of phone calls if it went wrong!
The largest individual switchover is expected to be that of Crystal Palace and its relays, potentially serving over 4.5m households. The biggest before that will be September's Sutton Coldfield/Emley Moor. By themselves, they serve 1.87m (SC) and 1.55m (EM), but both have a lot of relays. Winter Hill (2.69m) serves more households but it was done separately from any other.
The phased rollout has also allowed Arqiva to save a bit of money, by having a smaller stock of temporary equipment that can move from site to site as installations are upgraded, rather than having to upgrade everything at the same time.
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Michael: Can you tell us which channels you have, and which you don't have?
My guess is that you've got everything on BBC A and D3&4, and nothing from SDN, ArqA and ArqB multiplexes. I also guess that you don't have HD equipment, so nothing from BBC B.
Looking at the predictor, it's probable that the low power signals on SDN, ArqA and ArqB are just too weak, relative to the amount of interference, for you to get them reliably at the moment. While these temporary locations have double the power of the services that previously used those frequencies, the new mode requires slightly more than that. (SDN hasn't actually changed mode but it has taken over Mux 1's frequency, which used the more robust - but lower capacity - mode.)
There's probably nothing you can do except wait for next June. A different box might be able to handle the difference in levels better, or a slight repositioning of the aerial might help, but you should get a professional to check this.
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david wood: Are you actually using the Belmont transmitter? Your aerial would point north-west, across The Wash, if so. Digital UK's predictor reckons this is your best bet, but you would have needed to get a wideband aerial for best results.
Please note that this transmitter starts the switchover process, to increase digital power and move to clearer frequencies, tonight. The transmitter will be subject to interruption from around midnight (probably 12:20am as that's when the programme ends, though it could be as late as 1:10am) and will continue to be disrupted until 6am. The new high-power digital service should then be running reliably, and you must retune to pick it up.
If you never changed your aerial for digital, this should be a lot more reliable as it's replacing the old analogue BBC Two service.
As Brian says, the signal levels should be more than sufficient without amplification and it could cause distortion. If you find you can't get the BBC digital service from Belmont, or it's unreliable, remove the booster (if any).
The remaining analogue services will be switched off, and replaced by high-power digital services, on the morning of the 17th. Mux C and D will remain on low power temporarily until 23 November, until after Tacolneston has switched over. You will need a wideband aerial for these services.
Note that Belmont carries BBC Look North (Yorkshire & Lincolnshire) and ITV1 Calendar (Yorkshire) rather than the Anglia regional service. There are a number of relays providing this service. Your best bet is Kings Lynn, which will switch over with Tacolneston in November. At present it only provides analogue BBC One East and ITV1 Anglia.
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Briantist: You may not get a detectable signal from Ireland or Sudbury, but you will get interference. For Ofcom's 800MHz clearance consultation, Arqiva provided a plan of how to handle it, which details potential interactions between Mendip and Rouen and Cap de la Hague, should it be allocated C48 and C51 to replace C61 and C62.
However, I suspect this is in the 1% case (e.g. ducting), not general problems with reception.
John_Ha: I'd start by checking that cables are still making good contact and that the aerial is intact. Cable insulation does deteriorate with exposure to UV light and water penetration becomes a possibility - higher frequencies are affected worse by water problems than lower ones.
Amplification can also cause a problem - digital TV requires very linear response, it can't handle any significant distortion. If you have an amplifier or booster, try removing it or turning it down. Amplifier power supplies can introduce ripple if they start to fail, and ripple in the PSU causes ripple on the output, which again causes periods of drop-out or distortion.
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Nigel, Briantist, Keith: http://www.digitaluk.co.uk/transmitternetwork/tools__and__resources/almanac/installer_newsletters_transmitter_groups2009_pdfs/Belmont_and_Olivers_Mount_1MO_FINAL_July_2011.pdf says:
"Oliver's Mount and Hunmanby will carry the same regional news services as Emley Moor."
That'll be Look North from Leeds then.
The BBC call the Hull service Yorkshire & Lincolnshire.
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James: You will need to retune to continue receiving BBC channels, but other channels should still be fine as they haven't moved.
If you're using a communal aerial, the system may need adjusting for the new channels and signal levels - contact your building manager or landlord. It's possible that this work is currently being done.
If you're using a booster, try disconnecting it, as it may now be getting overloaded and distorting the signals.
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I realise it's a lot of work, but would it be possible to incorporate the interim stages for transmitters that can't go to final channels in one step?
I know that the information is available from Postcode Checker - Trade View (for example) but I find it more accessible in your format.
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Tuesday 2 August 2011 2:04PM
Steve Williams: That's why "ends" is in quote marks. Yes, the commercial multiplexes are often delayed as they have to have new frequencies allocated, which are often in use elsewhere.
Sudbury can't start using the channels ultimately allocated, because they're in use at Dover (BBC Two analogue and two low-power multiplexes). Dover BBC Two would cause a lot of interference to the multiplex using this frequency, and Sudbury high-power services would damage the two low-power ones at Dover, so you have to wait until after Dover switches over next June.
In the case of the change in November, Sudbury ArqB is currently using a frequency that will be needed by Tacolneston from 23 November, and so it takes over the one freed by Tacolneston on 9 November.
The problem mostly doesn't arise for the PSB multiplexes as they are generally taking over three of the four analogue frequencies, which are usually clear of interference for a large enough distance, because of the original analogue plans and the way that low-power digital was fitted around that.