All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
Neil: Firstly, this is the nature of reception of digital signals. With analogue, the picture gets gradually worse (more grainy) as the signal gets weaker.
With digital the picture works, up until a particular point (known as the "cliff edge") when it doesn't work. There isn't much inbetween where it "sort of" works.
Of course, there is no saying that the signal won't return, as whatever has changed to put it just below the threshold could go in the opposite direction.
Before switchover, different multiplexes use different modes. 16QAM is more resiliant than 64QAM at the same transmission power. Ch22 which carries ITV1, C4 and others broadcasts in 64QAM mode. Whether this explains why it has gone and not the others, who knows.
I suggest that you check your connections, perhaps swapping leads to see if they make any difference. Rather than using digital TV to determine whether there is any improvement, I would use analogue (looking carefully to see if there is any improvement).
Waggle the cables about at each of their ends and look for immediate changes to the analogue picture. Any such symptoms suggest poor connection, either the plug not making a good contact or (some of) the conductors in the cable are broken.
The centre terminal of female coax sockets can be tightened, but obviously don't put too much stress on it.
Crushed coax should also be avoided as it can have an adverse effect on the signal it carries.
It is all about ensuring that everything within your power that can be done is done.
If you don't have much joy, another possibility is to try tuning to another transmitter that has switched over and is therefore on its post-switchover full power.
Looking at the map, Sudbury might be your best bet. It is in the opposite direction to Crystal Palace, so you might be able to receive it, depending on your aerial.
This is a bodge, and may, of course not be faultless due to the aerial not being pointing in the right direction. But it might be better than Crystal Palace.
It's a try it and see kind of thing.
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Leon: If your aerial is on the New Barnet transmitter and you are receiving any Freeview channels, then they are not coming from New Barnet, and hence you are receiving signals from another direction and one to which your aerial doesn't point.
I had a look at your street on Google Streetview and the vast majority of aerials are on Crystal Palace. There are the tell tale signs that it is a bad signal area because of not only large aerials, but ones mounted high up.
Looking at the OS map, you are in High Barnet, so maybe you are just high enough.
I don't think that the satellite dishes will have an adverse effect on the terrestrial signal. They have probably been installed in such numbers due to the lack of Freeview.
Personally, I would leave the aerial as it is until switchover. You could make a change when the current aerial will work just fine after switchover. Or you could change it and find that it doesn't work properly after switchover.
If you get one good multiplex, then you're lucky and it might be a sign that a ten-fold increase in the power of the signal at switchover will see you getting them all.
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Ian McPherson: What is the make and model of this HD recorder?
Also, what is your location, preferably post code, so we might check on the likely signal at your location? It would be useful to know what transmitter you are receiving from, or what direction your aerial is pointed in (the latter certainly requiring a location in order to determine the transmitter).
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Ian McPherson: There is no reason why you can't use one aerial for each tuner in the box; that is the reason for having two inputs. That is, so that you can use different aerials on different transmitters for analogue and digital.
Of course, when analogue is switched off in your area, then you can disconnect the analogue tuner altogether.
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Leon: This is the nature of reception of digital signals. With analogue, the picture gets gradually worse (more grainy) as the signal gets weaker.
With digital the picture works, up until a particular point (known as the "cliff edge") when it doesn't work. There isn't much inbetween where it "sort of" works.
Of course, there is no saying that the signal won't return, as whatever has changed to put it just below the threshold could go in the opposite direction.
I suggest that you do the things that are within your power; checking cables and connections. Use the analogue signals to do this, moving cables and connectors and seeing if there is an immediate change to the quality of the picture which would indicate an issue with the cable. Swap the cable with another one if you have one. Is one better than the other?
See here for some ideas:
Freeview reception has changed? | ukfree.tv - independent free digital TV advice
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Elaine: There is no such thing as a "digital aerial" or an "analogue aerial". Aerials are designed to receive signals at particular frequencies or range or frequencies and what type of signals (analogue or digital) are doesn't matter. In some cases, new aerials are needed for digital reception, usually because the signals are outside of the frequency range that was previously used for analogue (and hence outside the aerial's frequency range).
Where a current aerial works and feeds one room, it is possible to split the cable using the appropriate device so as to supply two or more rooms.
It would be useful to know your current location (preferrably in the form of a full post code) so that the likelihood of reception may be checked upon.
What is the current aerial? Is it on the roof and what direction does it point in? You say that you have watched TV on your computer; do you not have a TV?
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Mrs P.Baigent: The likely answer (particularly as your neighbour is experiencing the same thing) is that the signal level at your location has dropped a bit, and that the level of the signal going into your TV is now just below that needed for the picture to show.
Retuning may only exacerbate the problem if the TV has the correct frequencies for the transmitter in question. It won't fix the problem (unless, perhaps, it is tuned to the wrong transmitter). You should refrain from retuning in such circumstances.
You need to retune on 28th March due to a change in frequency of some of the services. There is also a similar retune event coming up some time next year.
The commercial channels, including Pick TV are currently on low power from Mendip and will be so until 28th March.
To get the missing channels back, I suggest that you manually tune. Having got them back on your TV, do not retune, even if it starts to break-up or give "no signal". At such times, you might go to the signal strength screen and see that there is a weak signal there, but not enough to produce a picture.
Similarly, if you manually tune you might find that the signal is there but too weak to produce a picture. You will have to try again at a different time.
For a full list of Freeview channels, see here:
DTG :: DTT Services by Multiplex
This list shows which services are carried on which multiplexes. A multiplex is a group or basket of programme channels that are broadcast as one signal on a single frequency. For example, Pick TV and Dave are on the same multiplex (COM5: ArqA). If you haven't got Pick TV, then the same will be so of Dave (and other channels in that multiplex). Conversely, if you have one, you should have them all (in the same multiplex).
What you need to do is identify the multiplexes that you are missing and attempt to manually tune to them to add the missing channels. The three low power multiplexes that you might be missing are:
COM3: SDN (ITV3 etc) manually tune to Ch48
COM4: ArqA (Pick TV etc) manually tune to Ch67 (to change to Ch56 on 28th March)
COM5: ArqB (Yesterday etc) manually tune to Ch52
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tinytoes: See here for some ideas:
Freeview reception has changed? | ukfree.tv - independent free digital TV advice
I would put one of the analogue channels on (not Channel 5 though) and move the cables and connections about to see if there's any immediate change in the quality of the picture which might indicate a poor connection.
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susanuk: Have you looked in your 800s for the BBC channels (or indeed any channels)?
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Sunday 8 January 2012 7:41PM
kath: Happy to be of help to you.