All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
wutty: I'm afraid Digital UK shows no prediction for ArqA and ArqB at your address. It looks like the problem is that the channels clash with the Brierley Hill transmitter, which uses C53 and C57 for analogue services.
It's quite possible that the transmitting aerials don't radiate much, or any, signal for these multiplexes in your direction, at present. The Wrekin has separate low-power aerials pointing west and pointing east (the latter called 'The Wrekin B' in some sources), and before switchover the services used different frequencies on the two. Mux C and D were not listed under the 'east' set.
This will be resolved at the end of September when they move to the main antenna, on their final channels and at final power levels.
The HD transmissions are not compatible with older equipment. 'HD Ready' integrated digital TVs turned out not to be. Look for the 'Freeview HD' logo.
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Jonamat: Bren's 'answer' is no answer.
Waltham's transmissions moved because if they *hadn't* moved, many viewers' reception would have been damaged severely by the high-power PSB transmissions from The Wrekin, Bromsgrove and Lark Stoke.
C31 was believed to be a relatively clear frequency because up until last week, Sandy Heath had used it for high-power analogue transmissions, and the low-power digital transmissions were fitted around that. Bromsgrove used it for BBC One analogue on vertical polarization until early this morning. The Wrekin uses it for one low-power multiplex, but from the aerials that point west into Wales, not to the east. Lark Stoke uses it for one low-power multiplex but it's only 50W (this is up from 25W before switchover, but that's not a significant difference).
It sounds like you have a box that automatically retunes itself. Look in the manual for a way to turn this off - it's clearly storing the lowest frequency that it can decode rather than the best version. C24 is indeed D3&4 at Sandy Heath, and Sandy Heath is beyond Waltham in the direction your aerial's pointing.
Once you've turned automatic retunes off, delete all the Mux 2 channels, then manually tune C31.
You might want to replace the box because it will do this again after switchover - many multiplexes will be on lower channels both at Sandy Heath and at Belmont. Also see Digital Region Overlap.
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Should have added that the Crystal Palace early HD multiplex is also on C31, which is in the general direction of your aerial, but the weather conditions would have to be particularly specific for this to cause a problem. It requires an inversion in the upper atmosphere for the signal to bounce off of. Digital UK were giving this as a potential cause of problems, but I don't know whether they had a forecast or whether it's just part of their script.
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Steve: It depends what sort of standard you're talking about. HD Ready means the TV can handle 720- and 1080-line inputs from external boxes, using analogue component and digital DVI or HDMI, and supports 'content protection' on the digital input(s) using HDCP. That's it. The HD Ready TV 'works with the standard' by having an external box that decodes the signal.
Many people have simply assumed that an 'HD Ready' TV with an integrated digital tuner was going to be able to handle Freeview HD, and that's not the case. Some might be able to handle 1080-line MPEG 2 Main Profile@High Level, which France is using for their HD transmissions, on DVB-T multiplexes. Others might be able to handle MPEG-4 AVC which Ireland will be using for their HD services, again on DVB-T. But only receivers with the Freeview HD sticker support DVB-T2 and decoding the mildly-scrambled EPG data.
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Sandro: The Freeview HD website only tells you if HD is available from some transmitter in your vicinity, not necessarily the one you're using.
The best bet at the moment is the Sandy Heath transmitter, where HD services started at stage 2 of Digital Switch-Over, on the 13th of April.
The only other nearby transmitter broadcasting HD is Crystal Palace, for which the prediction is poor.
Hemel Hempstead won't start broadcasting HD until step 2 of its switchover, on 18 April 2012.
Sandy Heath should be good for all multiplexes now, though the predictor does show a probable deterioration on ArqA and ArqB multiplexes late next year (not clear why). The aerial needs to be oriented horizontally rather than vertically, and you'll get East Anglia news and other regional programmes rather than London. The predictions are more stable if you stick with Hemel Hempstead.
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MH: Check that the TV is actually tuning in C68 and not a distant version on a lower channel. The switchovers at Sandy Heath, Ridge Hill, Lark Stoke, Bromsgrove and The Wrekin mean there are now some pretty loud transmissions off to the sides, and if the weather conditions are right, the signal could be strong enough to be detectable, but not usable.
There should be a 'signal detection' menu somewhere which shows the UHF channel being used. If it's not C68, delete all the Mux 2 channels and do a manual retune on C68.
You are pretty close to the Oxford transmitter. An amplifier or booster will likely cause too much signal. Some people have found that the switch to the new aerial increased the signal levels and caused problems - if you don't have a booster, or removing it doesn't help, try adding an attenuator. 'Herringbone' patterns on analogue are an indication of having too much signal. All analogue channels should be perfectly clear at your location (certainly the first four), unless there is a problem with terrain, buildings or trees.
At switchover, the ITV1/C4 digital multiplex moves to C60, currently occupied by ITV1 analogue. There should be fewer problems.
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brian: Sandy Heath started transmitting high-power digital signals on C24 and C27 on 13 April, which will have made the problem worse.
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Nick Miles: There isn't much on C29 in the vicinity. The Ridge Hill (West) service started up yesterday morning, but this is at low power until after Waltham switchover and is much lower on the mast anyway. It's reserved for high-power digital transmissions from Waltham after switchover, so there are no switched transmitters nearby to clash with on this frequency. I'm really mystified as to why you would be having problems.
My best guess is that the removal of interference and move to higher channels has resulted in too much signal. Higher channels propogate less well, but most aerials have more gain the higher up the band you go, particularly Group C/D aerials which aren't intended to work down at the low channels. If you have an amplifier or booster, remove it, and if that doesn't help, try adding an attenuator.
My calculations are based on the postcode LE3 5GG, which is 70 Woodgate, Leicester.
You have to pay your TV licence if the TV is capable of receiving the signals. The broadcasters take care of broadcasting, you're in charge of reception.
The TV licence funds the BBC, and from what you say, you're getting their channels. ITV, C4 and C5 don't get a single penny from it, their business is selling viewers' eyeballs to advertisers, so you'd think they'd be interested in not selling yours.
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Helen: Your most likely transmitters are Emley Moor or Bilsdale. Do you get ITV1's Calendar (Yorkshire) or North East Tonight (Tyne Tees) news programme? A full postcode would help us to pinpoint the problem.
Predictions from both transmitters suggest that you should not need a booster for reliable results. They are of limited use with modern equipment, and can be the cause of problems if signals are already large.
High-power tests were run at Belmont between midnight and 6am on Wednesday and Thursday mornings, which could have introduced more signal than expected. DUK do predict that you would have a reasonable service on some multiplexes from Belmont, after it switches over.
For Emley Moor, your aerial would point roughly south-west. For Bilsdale, it's north-east. For Belmont, it's south-east.
If your aerial is pointing at Belmont, you'll be getting fringe reception of one of the other two (probably Emley Moor). You would get much better results by pointing the aerial to Emley Moor itself. If the aerial wasn't changed for Freeview it would be a Group A type, and it won't work well for Emley Moor, which uses Group B frequencies.
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Wednesday 20 April 2011 2:25PM
Chris: Yes, the Ridge Hill West transmission is a 'mini-mux' carrying only ITV1 and ITV1 +1. The legal framework does allow D3&4 to broadcast BBC channels, but the BBC would have to come to an agreement with the ITV companies and Channel 4 over how much it would cost.
The BBC have never shown any interest in providing a BBC West service to this area. The ITV service was only added in December 2006.