All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
Briantist: Changing the guard interval would not itself improve reception directly (except in rare cases of strong distant echoes, which are unlikely; 7.5km is plenty of distance to prevent this problem). It would improve only if the intent was to synchronize transmissions with another transmitter, in which case the overlap area would have constructive, rather than destructive, interference. It all hinges on the timing.
The nearest candidate using the same frequencies will be Chatton, when it switches over at the end of next year. For that reason, I doubt that it is to do with improving coverage.
Others are certainly reporting that the guard interval has not changed and therefore capacity has increased. The larger capacity is for the moment just carrying more null packets.
On its own, this change will reduce coverage slightly.
The retrofit is due to complete, at least for ArqB, on 23 November (Selkirk, and Tacolneston DSO 2), so we should know more then.
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Andrew Tegala: To be honest I'm surprised they're using Hannington at all. Slough was always considered part of the London TV region, and Hannington has restricted digital coverage to the east at present. Are there any trees or buildings in the direction of the Crystal Palace transmitter that could be blocking reception?
It is possible to combine the signals from two aerials, one pointing in each direction, but obviously that requires extra outlay.
If the system is channelised, it will currently be handling 11 frequencies (5 analogue, six digital) so there will be some spare slots on it after switchover. You only really need the three PSB multiplexes from the other transmitter, the channels on the SDN, ArqA and ArqB multiplexes are all the same throughout England.
Do a survey of your neighbours, see which service they'd prefer and if they'd be interested in receiving both. The management agent will want to recover the cost somehow, of course.
If the aerial was changed, everyone would lose reception until they retuned, so it would have to be co-ordinated carefully.
You should first check that it's not a problem of too much signal on the Crystal Palace services. What do you get on analogue? What does your Freeview box say if you try to manually tune in on C22 and C25? If the signal strength is higher than for Hannington services but quality is lower, it's likely that the signal level is actually too high - this could be considered a fault on the system.
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Tim: That booster? You probably don't need it.
Check that the box has actually tuned to Black Hill transmissions and not something else. The Kilmacolm relay transmitter is very close to you and uses lower frequencies, so could well be picked up when tuning, as older boxes often just store the first signal found when scanning. See Digital Region Overlap for thoughts on how to deal with reception from more than one transmitter.
Otherwise I'd be inclined to assume it's impulse interference caused by the thermostat or other central heating device (pump motor). Does it happen shortly after the central heating comes on?
If none of that sorts it, you can report the problem to the BBC at BBC - Reception problems . Select 'No' for 'Does this answer your problem?' and continue through.
Digital UK, and that BBC page, suggest that you can get a signal from the Strathyre Link transmitter, but I think that's very unlikely. It's probably what you'd expect to get from Black Hill if your aerial was pointing at Strathyre Link. My guess it's treated as a Single Frequency Network in the DUK predictor, but the sole purpose of Strathyre Link is to get the signal down the valley to the Strathyre transmitter itself, and hence is very, very low power (130 milliwatts).
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Tracey: The aerial might be pointing to the Heyshaw relay. This 'Freeview Light' transmitter only provides the channels you've mentioned.
You should be able to get a full service from Bilsdale - both now and after switchover. The chance of a full service from Emley Moor is slightly lower at the moment - the ArqB multiplex clashes with Multiplex 1 at the Pontop Pike transmitter that serves Newcastle. Belmont is also strong enough for a good service on the SDN multiplex as well as the public-service multiplexes.
For Heyshaw, the aerial would be aligned vertically - elements going up-and-down - and pointing west-north-west (291° on a compass). For Bilsdale, Emley Moor or Belmont it would need to be horizontally-polarized - elements going side-to-side. Bilsdale is roughly north-east (32°), Emley Moor to the south (190°), and Belmont south-east (129°).
You, or future tenants, might well be more interested in West Yorkshire news than Tyne Tees, so I'd recommend Emley Moor even though it might be a bit harder to get reliable results from there than from Bilsdale. It's likely that the aerial would have to be replaced, not just moved and rotated, but the cost of an aerial installation is mostly the labour cost anyway.
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Iain: The licensed combinations for ITV1 HD on satellite are:
Central
Granada + Border
London
Meridian + Anglia
Wales + West (+ Westcountry)
Yorkshire + Tyne Tees
That matches the ITV1 +1 regions licensed on satellite and Freeview. They also match ITV1's macro advertising regions. ITV are more interested in getting you the right ads than the right programmes.
However, so far, only Central, London, Granada, and Meridian/Anglia have launched on satellite and Freeview.
To get started quickly, I believe all 'early' Freeview HD services carried London, but they're switching to their own services as switchover happens. You might find that Yorkshire Tyne Tees (Emley Moor news) starts once the London region has switched over in April.
ITV might invest in more variants - including launching the two that they have licences for already - now that more capacity is available on the Astra 1N satellite.
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Ofcom's Table of Digital Stations version 6 has this relay replaced with 'Sunningdale', at the same power and height. This is the name of another building nearby, on Chapelhill Road CH46 9RG.
Wirral Metropolitan Borough Council were notified in May 2010 that the building carrying the Bidston relay was to be demolished: DEM/10/00628 at Wirral Metropolitan Borough Council Planning Pages
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Briantist: Reviewing the older documents, as the NGR in v5 doesn't match this grid reference, the grid reference, height and power were altered in version 5 of the document; only the name was changed in v6 (and the NGR was slightly altered).
New height is 55.3m, 4.8m higher than before, and the new power level is 30W, up from 25W.
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Alan: Signal strength should never hit 100%. You have too much signal already. If you have a booster, get rid of it. You will probably need to add attenuators to get back into range - or just replace the old perfectly good aerial.
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Bob Loader: With a prediction of 100% chance of reliable reception, chances are that you have too much signal. See Freeview signals: too much of a good thing is bad for you | ukfree.tv - independent free digital TV advice .
Another possibility is that your box has decided to tune in the signals from The Wrekin, which also have a predicted 100% chance across the board, as they are on lower frequencies. See Digital Region Overlap for how to resolve this issue.
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Thursday 27 October 2011 4:35PM
Briantist: Audio description is a secondary mono stream that starts and stops as required. That's true of SD services as well as HD services. For HD, audio description is encoded as HE-AAC - the requirement to use AAC-LC for the main audio stream is that chipsets generally can handle two different streams of AAC at the same time, they can't handle one AAC and one Dolby.
In Ofcom's Second Invitation to Apply, they included a 'Timing of the Fourth HD Service' document:
http://stakeholders.ofcom….pdf
which states (section 3.9) that 32 kbps would be allocated for audio description, in addition to the 192-384 kbps for the main multi-channel audio.
This was obviously before the service launched, so estimates were necessary. The 'Timing of the fifth HD service' document is very thin in comparison, because they're just saying 'the BBC said it was OK'.