All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
izzy: Perhaps you were talking about the Other Channels feature? There's an example for adding ITV1 HD at ITV HD on Sky+HD Boxes | ukfree.tv - independent free digital TV advice .
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C McGrath: ITV's channels do not appear in Sky's Republic of Ireland EPG. To add, follow the steps at ITV HD on Sky+HD Boxes | ukfree.tv - independent free digital TV advice but use 10758 V for the frequency and polarization. ITV3 is on 10906 V. Other frequency and service information can be found at Eurobird 1 & Astra 2A/2B/2D at 28.2°E - LyngSat .
If you're using an aerial pointed into Northern Ireland with a Saorview box, you may need to wait until the end of next year for signals to be strong enough. If you can get UTV reasonably clearly on analogue now, digital should work when Northern Ireland switches over.
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Graeme Pitt: Hannington digital transmissions use the same frequencies as Guildford's analogue transmissions. To avoid interference to the transmissions from Guildford, Hannington is severely restricted to the east.
This limitation will be removed when Hannington switches over, as services move to the main antenna at the top of the mast, which provides roughly omni-directional coverage. The PSB services will move on the 4th and 18th of February, with the COM services moving a little later on the 4th and 18th of April, when Guildford switches over.
It was proposed several times to remove this restriction, as it was believed that actually very few people in the Guildford coverage area would be affected badly enough. (One document admitted that Guildford had been made too powerful in the first place, covering too large an area.) Somehow, the change never occurred.
Signal levels can vary significantly over short distances, even without a restricted radiation pattern, so ideally you need to provide your house number as well as postcode when using the DUK postcode checker - your house may be in a different 100m x 100m grid square to the centre of the postcode.
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Lisa Thomas: So far, only the BBC digital services have launched at the Cop Hill transmitter. ITV1 and Channel 4 still only broadcast in analogue. They will go digital on the 21st.
You need to ensure that the digital TV is correctly picking up BBC Three on channel 7, BBC Four on channel 9, CBBC on 70, CBeebies on 71, BBC News on 80, BBC Parliament on 81, and the radio stations in the 700s. If so, you should be OK when the second stage occurs on the 21st. Work at Cop Hill should be completed by 9am.
Do note that Cop Hill will be a 'Freeview Light' transmitter, providing only the Public Service multiplexes. See Will there ever be more services on the Freeview Light transmitters? | ukfree.tv - independent free digital TV advice for more information. If you provide a full postcode we can check whether a fuller service from Emley Moor is possible.
Not being able to get satellite TV is unusual, but can happen if you don't have a clear view of the sky to the south-east. The satellites actually orbit above eastern Africa, over the equator.
Channel 5 analogue was very restricted in what frequencies were available, and was only available at larger sites, typically at lower power than the other four channels. Digital services originally launched wherever there was space, trying to maximize the population covered from as few sites as possible. The analogue switch-off is required to extend digital services, in order to free up the channels.
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Billy: That is old information. ArqB now transmits from the main antenna, which is unrestricted. However, there may be a clash with a relay that uses C57 for a different service. Can you provide a full postcode, so we can check the predictions?
I don't believe that a 20-odd element Log Periodic can have even 15 dBi gain. 6-7 dBd (=8-9 dBi, 0 dBd = 2.15 dBi) is much more likely. You could be reading the front-to-back ratio, which is also very important - this is just measured in dB as it is a ratio, not a quantity.
All relays simply retransmit what they received from the parent transmitter - all relays of Waltham will say 'East Midlands', including Nottingham which is fed via cables rather than off-air.
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Briantist: Did you ever see Arqiva's study on possible multiplexes 7 and 8 using the DDR frequencies? You might have missed it, as it is entitled "Ch 21 to 60: Creation of Layers 7 and 8 in released Spectrum".
http://stakeholders.ofcom….pdf
The section about Service Insertion Points, having to carry SI data for all multiplexes on each mux, and SFNs having to carry SI data for all regions that are part of the SFN, is quite interesting.
The new sites suggested, that don't carry the COM multiplexes after DSO, are Whitehaven, Camlough, Poole, Peterhead, Chartham, West Runton, Aldeburgh, Londonderry, Strabane, Exeter St Thomas, Weymouth, Stranraer, Cambret Hill, Newhaven and Eastbourne. They actually say 97 sites but only list 96; Rowridge VP is one of the 96 and I'm not counting that as a 'new' site.
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Steve: The only remaining step published is SDN to change to 8K mode and increase in power (and presumably move to the final antenna) on the 12th of October.
There may be engineering works to dismantle the antennas used for low-power digital services before switchover. The masts are now shared with mobile phone companies and carry DAB and FM radio services, any of which might require new aerials to go up or existing ones to be changed, which might occasionally cause interruptions, but major re-engineering shouldn't be required for another 40 years.
There is also going to be another retune at some time, to free up C61 for 4G mobile phone services. This depends on getting international clearance for whatever channel gets used in its place, so we don't yet know when this will happen or even when we will know.
In the international planning for digital TV, we did ask for C35, but that might still be released for other purposes, or for new multiplexes - it's unlikely to be the new home for BBC A or for one of the COM muxes, if one is bumped out of the way for BBC A to use.
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Geoff: At 25km from Mendip you'll probably be OK with a loft aerial, though you do have to ensure it's aiming through tiles rather than brickwork, and avoid reflective surfaces in the loft. I'd go with a 40-element log-periodic, see Online TV FM DAB Aerial sales .
See Loft and indoor aerial installations for TV, FM and DAB and http://wrightsaerials.tv/….pdf .
As the others have said, if you *can* fit it outside, you should. I'd still go with the Log40 or you could maybe go one size down.
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Andrew Lowe: Because analogue simply had one radio channel = one programme service, but the capacity of a digital multiplex can be sliced up many different ways to fit in many channels. The Service Information describing how each multiplex has been sliced up is continuously re-broadcast at very short intervals - your box *could* use that information to spot new channels and deleted channels, but unfortunately very few do.
An actual *retune*, a move of a multiplex from one frequency to another, is relatively rare, though as jb38 says, some sites (particularly Sandy Heath and Mendip) have had far more than others. Again, there is provision in the Service Information to describe a move of one frequency to another, but very few boxes implement it correctly.
Here, the pay-TV markets work much better than the open systems, because the provider (Sky, Virgin Media) is in full control of the hardware specification and have required that the boxes retune themselves automatically as required. Freesat equipment can require being put in standby before picking up a change, and some does require the user to select a retune.
The automatic retune features on a lot of Freeview equipment are a disaster if you're in an overlap area, as they will typically tune in the lowest frequency signals even if you specifically manually tuned to the best available. The newest equipment should handle this a lot better.
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Friday 9 September 2011 2:49PM
Graham: There are no standards in the UK specification for what these meters actually mean.
*Usually*, the strength meter is a percentage or proportion of the actual range that the box can accept, but the upper limit is typically the *combined* level of all received transmissions; with six high-power multiplexes, plus overlaps from other transmitters, it may be necessary to ensure that each received signal is quite a bit below 100%.
Different boxes will have different upper and lower limits on what they can accept.
The 'signal quality' meter on a lot of equipment shows you the proportion of data that was received without error, *after* all error correction was applied. Therefore it stays at 100% until signal quality actually drops enough for the error correction to fail, which you will be able to see or hear, making it useless for diagnostics.
Other equipment shows the Bit Error Rate, the number of bits that were corrected by either the first or second stage of error-correction. Really the best information for diagnosis is the pre-Viterbi BER, but many chipsets don't make this available. Professional meter equipment re-encodes the decoded data stream and compares it to what was received, to produce the Modulation Error Ratio (MER), but that does require extra hardware specifically for measuring, so I wouldn't expect consumer equipment to include it.
The Scandinavian standard, NorDig, now does standardize what these displays mean. Ireland's Saorview standard is based on NorDig 2.0 although with the UK's MHEG 5 profile for interactive content rather than NorDig's.