All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
Keith Hobbs: It looks as though the Chatton transmitter doesn't transmit much digital signal in your direction. This is only guesswork, but from the antenna heights given by Ofcom and the photos of the transmitter, it looks like digital signals come from a pair of Yagi antennas (they look a lot like reception aerials) just below the main cylinder. They appear to be pointing north-west.
There is also a cliff between you and the transmitter, just to your west, which is blocking line of sight to the transmitter.
As a result, Digital UK predict that the reliability of BBC multiplexes is variable at best, and ITV multiplexes is poor. You're not expected to get anything much on Mux C or Mux D at present.
After switchover, you should get a reliable signal from the public service broadcasters but commercial channels will be variable.
Signal levels do vary over time with changes in weather conditions - both the signals you do want, and the signals from other transmitters that you don't (interference). A change in reception can be down to changes at other transmitters, and you can probably expect it to get a bit worse in the year or so before switchover.
Do ensure that you have your aerial and cables inspected about every ten years. They deteriorate with weather exposure, which I imagine is a lot worse on the North Sea coast than in central southern England. Particularly, they stop working properly if water can penetrate the insulation.
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Paula: often this indicates that the cables were split improperly, or that water has been allowed to get into the connections. You're expected to get very good results at present.
At switchover, the power transmitted by the Sutton Coldfield transmitter will increase a lot. If you get clear analogue pictures now, you should get reliable results after switchover.
There's actually a very large difference between the analogue and digital signal levels from Sutton Coldfield. If the levels are too high, the high analogue levels can produce noise on the digital signals. Very high analogue signal levels can cause some noise on the TV picture, but it's often not very noticeable or is overlooked. If this is the problem you may well have more problems after switchover. It's really hard to tell you what to look for here because there was no standard for what the numbers on the signal strength meter actually mean. Only professional equipment is properly calibrated and gives meaningful numbers.
You could try adding an attenuator to reduce the signal levels and see if that helps. You may well need one after switchover.
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M
Sutton Coldfield (Birmingham, England) Full Freeview transmitteTuesday 29 March 2011 3:43PM
Reading
Adrian: Digital UK report that services are 'liable to interruption' this week. I'm afraid that this is all the information that they give out - we're not privy to exactly when things are being interrupted.
Most likely they're transferring services to a new set of transmitter equipment at ground level. I believe all work on the mast itself is now complete.
It's unlikely that they will be working overtime, so services will probably be back on this evening.
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Honest John: The problem is that because they're doing the switchover piece-by-piece, some previously working sites are compromised when others switch over. Where possible these are being balanced with power increases, but it's not happening everywhere. Also, the commercial multiplex power increases are often being delayed until later stages in switchover. Six multiplexes into four radio channels doesn't go, especially when you're also releasing about one-third of the channels. (The UHF TV channel allocations were designed for four networks only.)
In addition we're getting extra interference from the continent, as in many cases they're launching terrestrial digital TV for the first time. France seems to have completely reorganized its map, rather than reusing channels that they had used before. There has been co-ordination for the final frequency assignments, but I don't think there has for the current low-power Freeview channels.
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Mick H: I can't see any reason why you should not get those channels reliably right now. It's most likely that you have too much signal rather than too little, and this means it will probably get worse after switchover, not better.
You should remove any amplifiers that you have, and try adding an attenuator.
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M
West Yorkshire to get reduced Freeview service for two months |Tuesday 29 March 2011 4:14PM
Reading
Richard: This page relates to last year's events. If you have a current problem, please post on the transmitter page providing your full postcode.
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M
Sandy Heath (Central Bedfordshire, England) Full Freeview transTuesday 29 March 2011 4:36PM
Reading
Hertfordshaz: You will see increased power on BBC channels tomorrow, and on the Multiplex 2 channels listed above on the 13th of April.
ArqB (Multiplex D) reaches full power on 14 September, ArqA (Multiplex C) on 23 November, and SDN (Mux A) some time in 2012 after Hemel Hempstead switches over. You need to retune on each date, and also on 31 August when SDN moves out of the way of a change at Sutton Coldfield.
The main transmitter will be off-air from shortly after midnight to around 6am on both days. It's recommended to retune after 6am to ensure all changes are final.
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All: You can contact Channel 4 using the information at Broadcaster complaints details | ukfree.tv - independent free digital TV advice . (RG47SH)
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Ian Beech: Digital UK's predictor reckons your best bet is actually the Clun relay, 26km to your west. Clun requires a Group C/D aerial oriented vertically. This is a relay of The Wrekin, rather than of Ridge Hill.
You could just see how Ludlow works out - the predictor sometimes predicts no coverage but in practice it works out OK. The digital multiplexes will be using C45, C42 and C39, which are currently BBC Two, ITV1 and BBC One respectively. If you have a clear picture with no snow and NICAM stereo sound, and the tests on Ceefax/Teletext p284 are complete, you may be OK.
It looks like it's predicting no coverage from Ludlow because the SDN and Arqiva A multiplexes from Wenvoe (near Cardiff) will start using channels 42 and 45 from 27 April. Sutton Coldfield then starts using those channels from 21 September. Ridge Hill currently uses C45 for Multiplex D.
None of the relays transmitters will carry the commercial multiplexes. If you want those channels, you will have to look at Sky - most of them are not available via Freesat. The current list of Freesat channels is at Channels | Join Freesat (RG47SH)
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Tuesday 29 March 2011 2:15PM
Chris: It's probably because whatever region your box was previously tuned to was encrypted. Not all of the ITV, Channel 4 and Channel 5 regions are available free-to-air, some are only available encrypted (but 'free-to-view', you don't need an ongoing subscription).
The 'free-to-view' card is actually £25. You will need to get it sent to a UK address if you're in the Republic.
The address that the card is sent to is recorded on the card. That tells the box, in conjunction with data sent from the satellite, which ITV, Channel 4, and Channel 5 region you're in and therefore which frequencies to tune to and stream IDs to select for channels 103, 104 and 105.
BBC/ITV Freesat boxes use a different set of data (also carried by the satellite) to look up the postcode you enter and tune to the appropriate free-to-air frequencies and stream IDs.
You can also use the Add Channels feature to add your chosen ITV1 region, and a free-to-air Channel 4 region and Channel 5. See Eurobird 1 & Astra 2A/2B/2D at 28.2°E - LyngSat for a list of free-to-air channels on the satellites. See Freesat from Sky cards need updating | ukfree.tv - independent free digital TV advice for the procedure.
You may be thinking that Channel 4 and Channel 5 don't have regions. They don't have different regional content, but advertising time is sold on a regional basis so there are multiple copies of Channel 4 and Channel 5 carried on the satellites. (RG47SH)