All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
Steve: Your problem is that the Trefechan transmitter to your north-west uses the same channels, destroying your reception of these multiplexes. Trefechan uses channels for digital services that it used for analogue services before switchover - the commercial multiplexes at Wenvoe had to be squeezed in somewhere, and it's almost inevitable that there would be a clash for someone.
The commercial multiplex operators have refused the opportunity to transmit from any more sites.
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John Tidy: The problem is that grid aerials don't have very much gain, and have a fairly wide acceptance angle. At that distance from Crystal Palace, you don't need the gain, but you're still at risk of picking up co-channel interference from other transmitters, as well as increased likelihood of too much signal overall.
I would consider getting a small log-periodic aerial, which have better directional properties. You might need to add an attenuator to reduce overall signal levels.
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It could simply be due to weather conditions, of course: there are many other transmitters in the country using the same channels, which are normally blocked by terrain but in the right weather conditions, the signals bounce off the atmosphere and cause interference at far-distant locations.
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Charlotte: That's expected on ITV1 +1, because ITV are only transmitting macro-regions on the delayed channel. The whole of Anglia and Meridian regions get Meridian South-East news. The whole of Wales, the West, and the South-West regions get Wales. The north-east gets Yorkshire West while the north-west gets Granada. London gets London and the whole of the Midlands gets Central West.
It's not clear why this is. It may be because they only had six slots available on satellite, and only bought enough delay equipment for these six slots. (There may be some monitoring necessary to cut out programmes that they don't have the rights to broadcast twice in quick succession.)
If it's happening on the main channel, it's possible there was some failure in the news studio and they had to revert to a backup programme supply.
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Mr Costa Constantinou, Steve: I would be astonished if HD had not started, though I haven't seen anyone positively confirming that it has.
Freeview.co.uk's HD coverage checker seems to be pulling the information from the first transmitter reported by Digital UK's postcode checker. This seems to be reporting transmitters in a random order, so for Steve - because DUK give the results for Llangollen first - it's telling me that he can't get HD. Nonsense, the next transmitter (Cefn Mawr) is showing as 100%, and The Wrekin as 92%.
It seems to have trouble where the transmitter it considered most likely for analogue signals has now switched over. All the four transmitters shown for Steve are shown as 'Alternative Transmitter'.
If DUK's phone staff are using the same data - which they probably are - you can't rely on it.
Mr Costa Constantinou: can you provide the TV's make and model number?
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Paul Lowe: The predictions for Multiplex 2, A and D from Sutton Coldfield are indeed poor, most likely due to clashes with Winter Hill for Mux D and Emley Moor for Mux 2 and A. The Lichfield transmitter does provide HD services but they are weak, out-of-group, and aimed into Birmingham.
You could alternatively be using Waltham for East Midlands news services. If you are, you would have had to retune on the 30th of March and 13th of April to keep these services, as they moved frequencies. If your aerial is the wrong type - a Group C/D rather than a wideband - the gain at the new frequencies could be poorer than at the old frequencies. For a good-quality wideband it should be better.
Waltham does not yet broadcast HD services - it will start to do so from switchover on the 31st of August.
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brendon: We simply don't know yet.
My feeling is that they will not launch it until Mux C/ArqA has switched to its final mode at all transmitters that have switched over. They don't want a repeat of the Sky Sports debacle where channels are available in some areas but not others, and particularly where channels might be lost when switchover occurs.
The TBA barker is actually running on Mux D/ArqB, but there isn't space there for the actual channel - it is meant to be on ArqA. In regions yet to switch it will be on Mux B - actually run by the BBC, but who have had to close all the services that wouldn't fit into the space available on their post-switchover multiplex, making a lot of space available on Mux B.
There are a number of transmitters where the commercial multiplexes have been delayed, and are still running in pre-switchover modes and channels. Mendip ArqA will switch to the new mode (and final channel) on 28 September, as will The Wrekin, Bromsgrove and Nottingham. Lark Stoke switches at the end of August. Sandy Heath ArqA will switch on 23 November.
Other transmitters yet to switch are slated to launch in the final mode, even if they cannot launch at final power levels or on the final channel.
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Dave: I think you have too much signal. Remove any boosters or amplifiers; if that doesn't help (or there aren't any) add an attenuator.
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John Haigh: Atmospheric propogation affects all radio signals. Actually, if there is another digital signal on the same channel, it has a greater effect than analogue signals with a higher quoted power. A lot of the power of an analogue signal is wasted in the carrier, which only knocks out a small portion of a digital signal.
Your fundamental problem is that the hill to your west blocks line-of-sight to the Ridge Hill transmitter, which means that you have a much lower signal level than you otherwise would. Inversion affects are likely to increase the signal levels received from Ridge Hill at night, but also increase distant interference.
It's possible that the signal levels were good due to the high pressure around the 20th, and they've now dropped back to normal, insufficient, levels. The prediction is still for a good chance of getting a reliable service, at least at the moment, so you may want to get some professional advice as to why it's not working.
Because you're relying on indirect reception, your results are likely to be affected when Rowridge switches over next year - it will use the same channels as Ridge Hill for all services. Obviously, as it's beyond the horizon, this will depend heavily on weather conditions.
The maximum permitted signal level for the commercial multiplexes is 10 kW and has always been 10 kW in Ofcom documentation, at least since the commercial multiplexes were put in-group. (I have a document from 2007 that shows them at different channels.).
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David: Sorry - as far as we know, the answer is never. The commercial multiplex operators have refused the right to transmit from any more sites, and the regulator has decided not to force them.
If you were using the Frome relay because of 'ghosting' on analogue, you might now be able to get a full service from a main transmitter, but it does depend on the terrain. If you provide a full postcode we can check this. You're likely to need a new aerial, though.
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Thursday 28 April 2011 3:10PM
Karen Denton: No, I'm afraid that if you stop subscribing, the Sky+ box disables the recording and time-shift features. It also won't let you watch anything you have previously recorded.
You have to keep subscribing to at least the minimum entertainment package to keep these features.
You can replace your Sky+ box with a Freesat+ recorder, but the range of channels is slightly smaller - some channels are 'soft-encrypted' (known as free-to-view) which don't require an active Sky subscription, but do require a Sky box and viewing card. See the 'All Free Channels' page for a comparison.