All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
Niall Burns: Divis uses only Group A channels, so use a Group A aerial rather than a wideband one which isn't as efficient for Group A channels:
Digital TV Transmitters
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John McGovern: The UK now has a two-tier terrestrial television transmitter network. This has been the case where 8.5% of the population who can receive Freeview can only receive the Public Service Broadcaster (PSB) channels.
The Commercial (COM) broadcasters have no obligation to provide a Public Service and only broadcast from 81 transmitters serving 90% of the population.
See here for a more in-depth explanation:
Londonderry transmitter | ukfree.tv - 10 years of independent, free digital TV advice
Of those transmitters that do broadcast the COM channels (which carry ITV3 and ITV4), quite a few aren't as strong as their PSB signals. Hence there will be some who can only receive PSBs from these full-service transmitters.
The question is, which transmitter does your aerial face?
The Penryn relay is PSB-only and is adjacent to Budcock Hospital. It is on a bearing of 155 degrees and aerials for it are vertical.
The photos on Streetview show quite a few aerials pointing to Caradon Hill which is 38 miles away. It is on a bearing of 53 degrees and aerials are horizontal.
A few aerials face Redruth which is only 6.4 miles away, but which you live immediately at the bottom of a 80m drop. Aerials are horizontal and on a bearing of 297 degrees.
Caradon Hill and Redruth are full-service transmitters. If your aerial faces either then it is worth trying to manually tune missing channels.
There are three COM channels (signals) and each carries a number of services. ITV3 is on COM4. Also check to see if you have 11:Pick TV (COM5) and 15:Film4 (COM6)
The full list of Freeview services is here:
DTG :: DTT Services by Multiplex
You may be lucky and either be able to manually tune in the missing channels (perhaps doubtful as generally speaking we would expect them to be tuned during the automatic tuning sequence) or you may be able to replace your aerial with one that is sufficient to receive the COM channels.
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Channels for the two transmitters are:
Caradon Hill:
- COM4 = C21
- COM5 = C24
- COM6 = C27
Redruth:
- COM4 = C48
- COM5 = C52
- COM6 = C51
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Peter Henderson: The Streetview photos were taken in 2008 before switchover. I think that we can safely say that the pre-switchover digital signals would not have been available at Niall's location. It is perhaps also highly doubtful that the Black Mountain analogue Channel 5 signal would also have been available. So even if the four analogue channels could have been received from Divis, then this would have provided nothing extra over that of Newcastle.
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niall burns: I have had a few thoughts:
Can you see the top of the Newcastle transmitter tower (where the radiating antennas are situated) or are they obscured by Tollymore Forest? If they are behind the trees, then this could be a cause of poor reception. How did you fare for analogue? Was the picture changing such as during high winds? This might be an indication to the effects of the trees being in the path.
If you are receiving Clermont Carn and Newcastle you will be unable to combine the feeds using a diplexer due to the channels that each transmitter uses. If you have the feeds combined using a splitter in reverse, then, whilst it can work, results can be unpredictable and could therefore be a source of poor reception on one or both transmitters - try removing it and tuning to Newcastle without Clermont Carn connected.
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niall burns: In answer to your original question of whether reception from Divis is possible, it isn't possible to provide an exact answer.
It might be worth looking around to see what others have done. In Dundrinne Gardens there are (November 2008) some Divis aerials.
It appears as if Slievenaslat and Castlewellan Forest might be the difficulty in your area, although this is just based on looking at a map.
Digital UK Postcode Checker doesn't reckon Divis is a possibility, although such predictors are in no way infallible and it should therefore be taken with a pinch of salt.
It may be that satellite reception is the best option. There are solutions that allow reception of Freesat and Saorsat using a larger dish and two LNBs. Can't really advise more than that; try searching the internet for information.
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Adam: Without knowledge of your location so as to get an idea of predicted coverage it is impossible to answer such a question. A postcode or that of a nearby location such as a shop might be useful.
You should check to see that it is tuned to the correct transmitter (the one which the aerial faces) and not that of another transmitter. The issue could also be caused by too high a signal level which is generally a possible issue for those living close to a transmitter, and particularly so for high power ones.
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Mike Smith: Because there are only a handful of ITV1 HD regions. This is so as to not need equipment to produce HD feeds for each region or sub-region.
I'm not familiar with whether the regions that do have HD feeds produce their local news in HD.
Those regions that don't have counterpart HD feeds (such as ITV Meridian Southampton) we assume don't produce content in HD. Therefore if ITV were to change to having different regional feeds there would be no variance in the HD content available; local news would still be in standard definition.
BBC One HD does not broadcast regional news due to the same cost reasons.
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niall burns: You should confirm that you are tuned to Newcastle transmitter by viewing the signal strength screen. On BBC One it should be tuned to C50, UTV is C55 and BBC One HD is C59.
Is it all three of these channels that are playing up?
Perhaps it could be a possibility (800W @ 3.7miles) that the signal level is too high going into your receiver. This can appear as too little or too poor a signal:
Freeview signals: too much of a good thing is bad for you | ukfree.tv - 10 years of independent, free digital TV advice
If you have an amplifier then it might be worth trying removing or turning it down. Or you might need some attenuation (the opposite of amplification).
The former analogue signals from Newcastle were at 1,000W each. The power of digital signals to serve the same area are -7dB of the analogue which is 200W.
The power of the signals now are 800W each which is -1dB on the analogue. So in real terms the signal is stronger than the former analogue.
You might be able to build a crude attenuator (prior to getting a proper one) by connecting only the inner core of the aerial lead by leaving the screen disconnected for a short distance (a few CM maybe). This will hopefully "loose" some signal.
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Wednesday 28 November 2012 8:05PM
Robert Fairbrother: Indeed. Even better, the issue "really ought" not to happen in the first place.
This is the nature of engineering work of any nature; it is usually impractical to give a timetable of the prospective turning of every screw. One assumes that the periods of low power and outages are kept to a minimum.