All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
Jon-G: The list of relays and times is at Digital UK - Relay transmitter switching times . Some will be off-air until 3pm.
Since relays simply retransmit what they receive off-air from the parent station (which for some relays is another relay), you can't put up a caption specifically for the viewers of that relay. Also, most people don't know which relay they're using! (They usually don't even know which main transmitter provides the service.) Most relays only serve small pockets that aren't covered by a larger transmitter. It's very hard to target communications specifically to viewers who will have a long outage, so you just get generic messages of 'could be off 'til lunchtime'.
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Steve P: Nottingham is part of Waltham's group and would display East Midlands.
Dave Jenks: The work was being done this morning in daytime, expected to finish at 12 noon, rather than in the early hours. It could be that services were off-air when you retuned.
Do check Digital Region Overlap, to see if anything there applies to you.
Digital UK predicts a variable service from the Nottingham relay for you, you're expected to get a much better service from Waltham or Sutton Coldfield. If the aerial points south-west, and is oriented with the elements going side-to-side, the box *should* tune to Sutton Coldfield as that's what the aerial is pointing at. If it points slightly south of east, that's Waltham. If oriented vertically - elements going up-and-down - and pointing roughly due north, it's aimed at the Nottingham relay.
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Jack Johnson: There will be no need whatever to do that after switchover, and there is no prospect of any changes being made before switchover.
There are no free channels in this area - Fawley Channel 5 had to close to allow Rowridge to take over C37 - and the 2K mode doesn't lend itself to Single Frequency Network operation.
You should replace the aerial entirely. They are not designed to work with elements missing and are not designed to have parts replaced, either.
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John Ormerod: HD services start from Rowridge at the second stage of switchover, 21 March 2012. I don't know where the November date has come from, perhaps you are close enough to a West or Westcountry transmitter that the Freeview HD site (which scrapes the Digital UK predictor results) thinks you can get it from there - though this would be November 2009 or November 2010. The only transmitter site switching over *this* November is Tacolneston near Norwich.
The line-up for regions that have switched over is currently:
BBC One HD
BBC HD
ITV1 HD
Channel 4 HD (4hd)
BBC One HD, ITV1 HD and 4hd are all simulcasts - they broadcast exactly the same as the SD version of the channel. If the programme was made in HD, the HD version is broadcast, otherwise the SD programme is 'upscaled' to 1080 lines. The exception is that BBC regional news is not yet carried on BBC One HD - when this is on, BBC One HD broadcasts a caption telling you to switch to BBC One.
BBC HD always broadcasts HD content. This might be a simulcast of something on BBC Two, BBC Three or BBC Four, or it might be another programme made originally for one of those channels in HD.
It is expected that by the time Rowridge switches over, a fifth HD channel will have been squeezed in, but the decision process of what it will be has only just started.
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Nicholas: The + or - indicate that the centre frequency of the transmission is +167 kHz or -167 kHz from where it would normally be. There's enough margin either side that it stays within the 8 MHz bandwidth.
As to why they do it - before switchover, it was to keep the transmission further away from an analogue signal that could interfere.
After switchover, offsets are used to keep those transmissions further away from neighbouring frequency bands. C21 usually gets a + to keep it away from anything below (e.g. emergency services TETRA radio).
Originally, C62 was going to be the top channel, but C61 and C62 are now going to be released so C60 becomes the top channel and gets a - offset. C31-C40 were going to be released too, so C30 gets a - and C41 a +. However, C39 and C40 are now retained (in place of C61 and C62), so C39, the new band edge, gets a + where it's used.
If one channel has to have the offset at a transmitter, an adjacent channel might also have one, to keep the inter-channel spacings. In extreme cases, all channels get an offset. For example, at Caldbeck, where 9 channels are required for all multiplexes as it carries Scottish and English versions, the lowest channel is C21 and gets a +, which causes C22 to need a + offset, which causes C23 to need one, and so on.
Low-power relays are generally allowed to have more emissions out-of-channel anyway, so typically don't have offsets.
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John Dusconi: My guess is that you were away when Sutton Coldfield switched over. You need to do a full retune of your box. Look for a full retune, default setting, full reset, first-time installation, 'virgin mode' or 'reinstall all channels' option.
If the manual doesn't make it clear how to do this, try looking at TV Re-tune .
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Mr B: The messages cannot be customized for each relay transmitter. The whole point of the relays is that they just retransmit what they receive from the parent transmitter. If the message said '6am' that would be wrong for some of the relays. So it's left a little vague.
If the message listed all of the times for all relays, it wouldn't be any more helpful as viewers generally don't know which relay they're using.
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Aynsley: You might get a weak analogue signal from Hannington, which doesn't switch over until February.
Some DVB-T2 equipment measures T2 signal strengths differently from DVB-T. It's not clear whether you're measuring values from the same card or from multiple cards.
The HD mux from Oxford does indeed use BBC One's old channel, C57. Analogue had to be switched off to allow high-power digital to use the old analogue channel allocations. It was a good plan in the 1960s and so it forms the basis for the post-DSO plan too - it means that nearly everyone should be able to get the PSB multiplexes with no changes to their aerials or communal systems, even those which only distribute specific frequencies.
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Chris.SE: The move to C67 was a very late-breaking change, the Digital UK Installers Newsletter describing today's retune was issued on the 29th of August showing the move to C56 (with no offset), then reissued a day later showing the move to C67.
The trade view when plugging in a postcode does show the correct information, but the 'trade region' page doesn't.
Ofcom's most recent licensing document http://licensing.ofcom.or….pdf also shows C67 from 28/9/11 to 28/3/12.
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Wednesday 21 September 2011 8:51AM
bill whyte: See Digital Region Overlap. My guess is that your main TV simply stores the first version it finds, not the best quality or strongest: the Belmont transmissions are on the lowest frequencies.