All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.M
My Freeview box has no EPG, is blank on FIVE, ITV3, ITV4, ITV2+Tuesday 8 February 2011 11:51AM
Reading
dave: sadly 'HD Ready' does not mean Freeview HD capable. It only means that the TV can handle external HD sources and has at least a 720-line display (1080-line for 'Full HD Ready').
Freeview HD uses a transmission method that wasn't even thought of when most HD Ready sets were designed and manufactured.
You will need to get an external Freeview HD set-top box or PVR, or buy a new TV.
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Oxford transmitter - service restricted until end of September Tuesday 8 February 2011 12:03PM
Reading
Tony Mallett: perhaps you should actually contact the broadcasters rather than posting here? This is a 100% volunteer website where people with some knowledge about aerials and cabling choose to contribute. We're not aware that anyone with any power to make changes even bothers to read it.
Brian has replied to your message, on the page you left it on, already.
The tone of your message tends to drive volunteer contributors away.
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Tony Mallett: some viewers in the area have found that the new transmission aerial produces higher signal strength than the old, and that causes problems with amplifiers. If you have an amplifier or booster, I suggest removing it to see if that improves matters. If not, try adding an attenuator to reduce the signal strength.
If you could provide your postcode, we can look at the prediction and the distance to the mast to see if your problems are more likely to be too much or too little signal strength, or other types of interference.
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Sutton Coldfield (Birmingham, England) Full Freeview transmitteTuesday 8 February 2011 12:17PM
Reading
Jayne Knight: you should point your aerial to Sutton Coldfield. The Lichfield transmitter only transmits analogue Channel 5 and the early Freeview HD service. In September Lichfield will shut down completely and HD service will move to the Sutton Coldfield transmitter.
However, aerial positioning is not an absolute process, and it can sometimes be beneficial to point the aerial slightly off-beam, to reduce pick-up of another strong transmission in a similar direction. The aerial basically picks up signals in a cone in front of it, rather than just immediately in front.
It's likely that some aerials are aimed slightly north of Sutton Coldfield, to improve pick-up of C5 from Lichfield, and to avoid picking up the transmitter known as The Wrekin, which is to the south-west of SC.
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Sutton Coldfield (Birmingham, England) Full Freeview transmitteTuesday 8 February 2011 12:21PM
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Brian: in looking up that last response I noted that the frequency plan for Sutton Coldfield has changed. ArqB will now use channel 39, and BBC B will now use channel 40, both with a positive offset.
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Nick: because the frequency of the HD service is slightly higher it will travel slightly less well than the SD service. However, if this small difference were enough to disrupt the HD services, I would expect that the commercial multiplexes - which are on half the power *and* at higher frequencies - not to work at all.
I do note that the SDN multiplex is on C48, the adjacent channel to HD services on C47. If overall signal strength is very high, it can overload amplifiers and cause signals to bleed into adjacent channels. I would expect this to happen both ways, though, and channels on the SDN multiplex to be equally badly affected (or, considering the lower power of the SDN transmission, worse). If you have an amplifier, try removing that - if the splitter is amplified, try a non-amplified splitter as Brian suggested. If that doesn't help, try adding an attenuator.
A final thing to check is to ensure that the HD receivers is actually tuning into Redruth C47 and not Caradon Hill C22, which has nearly as good a prediction for you, if the right aerial is oriented in the right direction, but will be substantially weaker if picked up as a side transmission. Freeview HD boxes are supposed to tune into the best signal, though, rather than just the first found.
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Paul: Before the main transmitting aerial was replaced, there were panels on top of it. These were used, the best I can tell, to increase the power-handling capability of the main aerial. The first four analogue channels and the six multiplexes were all combined onto the cylinder.
Multiplexes 1 and B also have supplementary panels below the main aerial, on one corner of the mast. Channel 5 analogue has its own skew-fire panels further down.
Source: U.K. Television Stations (UHF Digital System) and Former U.K. Television Stations (UHF Analogue System) showing muxes 2, A, C and D at an average height of 289m above sea level (AOD) and muxes 1 and B at an average 277m, and BBC1/2/ITV/C4 at 289m. Photographs at mb21 - The Transmission Gallery - 277m is actually in the middle of the FM radio panels immediately below the main antenna.
The mux 1 and B panels were moved down closer to the C5 array in order to fit the new reserve aerial, which took over services in late 2009 to allow the old cylinder to be replaced: http://tx.mb21.co.uk/gallery/oxford/oxford06.php
The new aerial was fitted in February 2010: mb21 - The Transmission Gallery . When the broadcasters tried to put it into service it caught fire, and had to be replaced.
The new, new aerial was fitted in August 2010 and went into service towards the end of the year. As far as we know, all services (except C5 analogue) are combined onto this one transmission aerial, just as before. At switchover all six high-power digital multiplexes will be combined onto this one aerial. (RG47SH)
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My high gain aerial can't get all the Freeview channels I eWednesday 9 February 2011 4:12PM
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Michelle: it sounds like these were room aerials. Digital does not work well with room aerials, particularly at the current relatively low power levels.
If there is already an aerial on the roof, or in the loft, or there is an aerial socket provided in the room if this is a block of flats, connect the TV to that - whatever the old TV was connected to. Then, if there are still problems, please ask again.
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Iain Marshall: the aerial has basically a cone of acceptance and that cone is wider than 3°. Particularly with loft installations, you frequently have to move the aerial away from line of sight to avoid, or at least reduce, picking up reflections anyway. It doesn't matter all that much. Just move the aerial to the place where it produces the best results.
You can see some diagrams of the actual polar response of typical aerials at Aerial Polar Reponse Diagrams .
Professional installers should be using equipment that shows the Modulation Error Ratio - how far the actual received phase and relative signal strength are from the ideal. Higher numbers are better. For example, the PROMAX TVHUNTER -http://www.dastv.co.uk/shop/Promax_TV_Hunter_Terrestrial_Meter_2423.php . Unfortunately the price of this equipment puts it outside the range of the DIY installer. (RG47SH)
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Monday 7 February 2011 2:30PM
Reading
Brian: why don't you just remove the erroneous NEW7 and NEW8?
There is no date even set for interleaved spectrum auctions. There is no guarantee that the spectrum auction will be won by any TV provider. The speculative allocations - and they were only ever suggestions - will have to be completely redone, since channels 61 and 62 are now to be released for mobile phone use. Previous allocations of 61 and 62 - either to existing muxes or tentative interleaved allocations - are planned to be moved to 49 and 50, and 49 and 50 to 39 and 40. However, some transmitters that haven't yet switched and currently use C39 or C40 for an analogue service are now to use that channel for a post-switchover digital service, according to Ofcom's latest documents.
NEW7 and NEW8 are causing problems on a number of transmitter pages where a real mux is temporarily allocated to those frequencies (e.g. Mendip). It's also sowing confusion among users expecting new services to launch at switchover.
I suggest removing NEW7 and NEW8 until we know what is actually going to happen - probably not for another two years unless Mr Hunt tries to push through his local TV proposals sooner (which will cause chaos, but politicians aren't known for their understanding of technical issues).