All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
Andy: See postings by Nick immediately above yours. He is a stone's throw from you off Woodbridge Walk and says that in his area only Public Service channels can be received.
See the terrain plot from the Sudbury transmitter to your approximate location:
Terrain between ( m a.g.l.) and (antenna m a.g.l.) - Optimising UK DTT Freeview and Radio aerial location
As you can see, the path of the signal runs close to the ground for quite a few miles. Obviously there are objects on the ground, so it is not surprising that reception isn't good.
Imagine if the transmitter was sending out a beam of light, then consider trees and buildings that are likely to be in the way.
See here for the full list of Freeview services:
DMOL Post-DSO Multiplex Channel Allocations
The PSB multiplexes are the Public Service Broadcaster ones. The COMs are the Commercial ones which have limited coverage with respect to the PSBs. Nick has been unable to receive the COMs from Sudbury.
Based his comments, I get the feeling that you may well be limited to Public Service channels. Or the COMs may be intermittent. Which channels are causing problems (PSBs, COMs or both)? Does each caravan have its own aerial?
Digital UK predictor considers Sudbury to be "marginal" at your location, and likewise Aldeburgh. The latter is PSB-only.
The predictor should be regarded as a guide. Local obstructions such as trees and buildings aren't taken into account. It may be a clue as to likelihood of success of reception.
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Janine Hindmarsh: Shotleyfield does not broadcast Freeview yet; it currently only carries the four analogue channels.
If their aerial is directed to the Shotleyfield transmitter it will be vertical. If they have been receiving Freeview with it, then they have been lucky!
There is engineering works ongoing at the various transmitters in preparation for switchover. Perhaps this is the cause of the (perhaps) slight change in signal which has resulted in them being unable to pick it up.
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As a PS:
After switchover, Shotleyfield will broadcast only Public Service channels which are BBC, ITV1, ITV1+1, ITV2, Channel 4, Channel 4+1, E4, More 4, Channel 5 and the four HD services.
The transmitters that broadcast Freeview before switchover will carry the full range of channels after switchover. In that general area these are Pontop Pike and Fenham.
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Pippo: See Freeview signals: too much of a good thing is bad for you | ukfree.tv - independent free digital TV advice
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Janine Hindmarsh: I have had more of a look at this.
In a valley, which transmitter(s) can and cannot be received from can vary house by house. So my comments are general.
From what I can see, Pontop Pike is the only likely Freeview transmitter that "may" be received in the general area of your parents. With this in mind, they must have been receiving Freeview with the aerial facing another way and of opposite polarisation (aerial vertical whereas signal is horizontal).
This perhaps suggests (I remind you that I can only be general) that the signal is strong and that reliable reception from Pontop Pike "may" be possible with an appropriate aerial aligned correctly.
If they continue with their aerial directed to Shotleyfield, then until switchover, intermittent reception of all channels is possible (due to them being picked up from Pontop Pike).
Come switchover, as Shotleyfield will only carry the Public Service channels, then they will be expected to be OK as the aerial faces the transmitter. Because it won't carry the Commercial channels (ITV3, Pick TV, Film4, Dave etc), then should the receiver pick them up, which it may do, then they can only possibly come from Pontop Pike, so reception may be poor, intermittent or non-existant (a bit like now).
For this reason, they may decide (or you might think it a good idea to advise them) that they have an aerial on Pontop Pike now. I remind you that what I've written is general, and it is also the case that an assessment of whether reliable reception from Pontop Pike is possible can only be made by an installer on site.
The Commercial channels have limited coverage which is about 90% of the population, whereas the Public Service channels serve everywhere that the current analogue does. In some cases, reception may be possible from another transmitter that carries the Commercial channels.
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Dee: Based on the fact that you are only 9 miles from the transmitter, the problem may be too much signal. See Freeview signals: too much of a good thing is bad for you | ukfree.tv - independent free digital TV advice
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Nick: When a receiver goes through its automatic tuning process, it scans all channels. Having done this it then has to "decide" which of the channels it is to go with, where duplicates are found.
In this case it is going with those from Aldeburgh. This is obviously not the desired result.
The solution is to unplug the aerial for the first 30% of the scan so that it doesn't get the chance to "see" the Aldeburgh channels.
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david C: The predictor thinks that Tacolneston may be more reliable at your location.
Due to this, confirm that your receiver is tuned to Sudbury for all channels, and not to Tacolneston for some.
This information (UHF channel/frequency that it is tuned to) is usually given on the signal strength screen.
PSB1 | BBC One | Sudbury=C44 | Tacolneston=C55
PSB2 | ITV1 | Sudbury=C41 | Tacolneston=C59
PSB3 | BBC One HD | Sudbury=C47 | Tacolneston=C62
COM4 | ITV3 | Sudbury=C58 | Tacolneston=C42
COM5 | Pick TV | Sudbury=C60 | Tacolneston=C45
COM6 | Yesterday | Sudbury=C56 | Tacolneston=C50
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Nick: I sympathise with your predicament.
The Commercial broadcasters were not mandated by law to follow the same coverage as the Public Service Broadcasters. This can only come back to politics rather any deficiencies in the engineering of the network. They follow the laws of capitalism which means that if it isn't worth it then it doesn't get done. They operate to provide them with a return.
After switchover, the Commercial broadcasters use less error correction so as to give them more space to fit in more services. This means that the signals are less robust than the PSB ones.
See the newsletter about the retune last November:
http://www.digitaluk.co.u….pdf
It says that on 27th June 2012 SDN would adopt 8k mode, but it makes no mention of this for ArqA and ArqB, so perhaps they were already in 8k mode (with the less error correction).
Nick, you did say that you could get ITV3 better when it was at 14kW, and it is carried on SDN which was in 2k mode then (and presumably more error correction than now). So the change in error correction could perhaps be the dampner, irrespective of power increase.
When you consider that the signal path to Hollesley runs low to the ground for miles, then perhaps this explains why the less robust COMs aren't available. That is, they are getting "bashed about" too much.
In which case, it would seem logical to suggest that the amplification of only the COMs I suggested above may NOT do the trick because the problem is more likely to be poor quality signal (for which amplification won't solve).
This leads me on to wonder if you would be better off with a lower gain aerial and amplifier. The objective being to get a better quality signal due to the wider acceptance angle. Obviously a lower gain aerial gives less signal strength, which is why an amp is necessary. I have seen this suggested as being an improvement on a high gain aerial in cases such as at the bottom of a hill, perhaps lined with trees. Perhaps the professionals could comment how likely this might help Nick.
It is, of course, always a possibility that reception may be variable owing to rain, leaves on the trees and so on.
Your other possibility is to diplex your aerial on Dover for the COMs with one on Sudbury or Aldeburgh for the PSBs. Obviously Dover may also be subject to variable reception. Its SDN and ArqA are co-channel with two of Tacolneston's PSBs. Your aerial will also be facing the Continent which could increase your chances of suffering under lift conditions. Also, the fact that the signal isn't strong due to your distance probably means that it is more susceptible to being knocked out due to interference from other stations that are co-channel under certain conditions.
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Nick: Of course, as you say, the best thing is to wait until the reported engineering work at Sudbury is completed to see what you have then.
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Monday 2 July 2012 7:20PM
Alan Murray: Yes, Freeview HD is operated by the Public Service Broadcasters and is therefore available from all transmitters.
It is the Commercial services that don't have as good a coverage, as you already know and this is because they have no "Public Service" obligation.