All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
Alain: Yes, you can get some dishes with two LNBs. Or you can get a replacement mount to allow two LNBs. See BrySat Info - 2 satellites, one dish for an example.
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Jane Ashton: You're most likely using the Rowridge transmitter on the Isle of Wight, which switches over next March.
Digital UK predicts a good chance of reliable reception now on Mux 1, 2, A and B, while C and D are expected to be variable. It's always more difficult on a long sea path, and you also have to contend with interference from northern France - I believe they are further along in their switchover than we are.
A new, taller mast has been built at Rowridge, to the west of the old mast, to improve coverage after DSO, but I'm not sure whether services use this mast yet.
It's still worth checking that your aerial is intact and pointing the right way, and the cables are in good condition. Cables should be well secured so they can't move about when the wind blows - if they have been able to move, they may have worn away the outer insulation against tiles or brickwork, or just pulled out of the connection. Also, the insulation does perish with exposure to UV light - as a rule of thumb, outdoor cables last about 10 years. Damaged insulation lets water in, which increases the amount of signal lost along the cable and can damage equipment if it manages to run all the way along the cable.
For other ideas, see 'Freeview reception has changed'.
The postcode predictor reckons that you'll get a very good chance of reliable reception from the PSB multiplexes after switchover, but the COM multiplexes may be variable. Once they reach their final channels on 18 April 2012, you will get better reception by rotating the aerial so the elements go up-and-down rather than side-to-side, as Rowridge will then transmit more power on vertical polarization than horizontal. Don't do it until then, as it doesn't use vertical polarization at all until switchover.
The change to VP is intended to combat interference from French stations.
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Mike Roberts: Yes, you're likely to get the channels more reliably than you do now, though this is never going to be all that reliable with the Pennines in the way. The commercial multiplexes will be co-channel with those from Moel-Y-Parc so are unlikely to work.
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dan: Is your box quite old, say 2002-2004? If so, it may not support the 8K mode used after switchover. You can find a list of some boxes known to have this problem at http://www.digitaluk.co.u…ment .
It might also possibly be a box that struggles with the Split NIT introduced in 2008 - the problem doesn't show up until you retune. Some affected boxes are listed at http://www.digitaluk.co.u…tnit . You might find the BBC channels up in the 800s, or somewhere else in the channel list. As KB Aerials says, you might also experience this if your box stores the first-found at the preferred channel number, and the signal from Belmont or Chesterfield is powerful enough.
If you're very close to the transmitter you might find that your signals are now too strong. I can check this if you provide a full postcode. If you have an amplifier or booster, try removing it.
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pete from Ewden: The Oughtibridge relay will switch over on 7/21 September along with its parent, Emley Moor.
Digital UK predicts that 99% of locations, within the 100m x 100m square that the centre of your postcode is in, should get reliable reception.
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Briantist: £25m is about what Arqiva and NGW said they would be charging a PSB for transmission from all 1,100 site, in 2005 money.
As far as population goes, re-read page 2 of 3 of Ofcom's document for the definitions of 'Gross Population' and 'DPSA Population':
"Gross population represents the total number of households that could receive the local multiplex if their aerials are pointing towards the appropriate transmitter.
"DPSA is an attempt to provide a more realistic estimate of the number of households that might be able to receive the local multiplex than gross population. The DPSA (Digital Preferred Service Area) is a prediction of the areas where a particular transmitter is likely to provide better signals than other transmitters. In those areas, it is reasonable to expect that households have aerials pointing at the transmitter in question and could therefore receive the local multiplex broadcast from that transmitter."
Where more than one transmitter is used, the 'gross' figure is the largest from any *one* transmitter, but the 'DPSA' figure comes from the sum of *all* transmitters. That has led to a few anomalies where the DPSA figure is larger than the gross figure.
If you're trying to represent the actual populations of those areas, might I suggest using List of largest United Kingdom settlements by population - Wikipedia, the free encyclopedia or List of urban areas in the United Kingdom - Wikipedia, the free encyclopedia - however, that is people, not households. If you're going to adjust a population figure to get approximate count of households, using a figure for average occupancy, you need to *divide* by 2.41, not multiply.
On that basis I reckon you get 369,804 / 2.41 = 153,445 households in the Reading/Wokingham urban area, and therefore the proposed local multiplex would cover 235% of them on a gross coverage basis, 91.2% in DPSA.
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mr chaplin: Presuming you're not paying Sky for a subscription, see Compare Freeview and Freesat-from-Sky TV | ukfree.tv - independent free digital TV advice for the channels that broadcast on Freeview but not on Freesat-from-Sky.
See Compare Freeview Light and Freesat-from-Sky TV | ukfree.tv - independent free digital TV advice for a comparison of what's available from the Mynydd Bach transmitter with what you can get on satellite.
Digital UK's predictor indicates that you have a very good chance of reliable reception, of all channels, from the Wenvoe transmitter.
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mike Roberts: You often see claims that line-of-sight to the transmitter is required. It isn't. You definitely get the best signal levels if you do, and the least reflections, but you still get some signal (not necessarily enough to be usable) from refraction over the terrain.
Line-of-sight is also suggested because it is easy to compute possible signal levels. Most predictors - other than Digital UK's - use a simple free-space equation which can overestimate levels.
Aerials have a fairly wide acceptance angle - how wide depends on the aerial. It's likely that it has enough gain in Emley Moor's direction, not enough in Moel-Y-Parc's direction. Briantist is completely wrong to claim that a Yagi-type aerial receives as much signal from behind as in front, it is in fact far less (though not none).
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Betamax_Man: It's likely that your box has an automatic retune function, and that it also stores the first version of the channels that it finds, rather than the strongest. I would turn off the automatic retune.
At switchover, the best approach is probably to unplug the aerial before doing a reset. You can then plug it in when the scan reaches about one-third of the way through, or leave it out until the end, accept that it hasn't found any channels, then manually tune on the appropriate frequencies. See above for the UHF channel numbers to use.
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Wednesday 10 August 2011 2:20PM
Steve P: You cannot stop a transmission at an arbitrary boundary. If the signal is strong enough to be received in all parts of the coverage area in Liverpool itself, there's inevitably going to be some bleed over into areas beyond the city. This isn't intentional coverage, though it will cover some 'dormitory' areas.