All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
Sally: Which post code are you in?
Along Federation Road there are aerials pointing to the main transmitter at Crystal Palace and some which are pointing to the Woolwich. If it's the latter then it only broadcasts the PSB (Public Service Broadcaster) channels, so no ITV3, ITV4 etc.
Crystal Palace aerials are set horizontally (elements flat) and point north west.
Woolwich aerials are set vertically (elements up/down) and point a bit clockwise of south west.
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Sally: I think the area you're in is very difficult for reception from Crystal Palace, which is the main transmitter which broadcasts all channels. For that reason what can and can't be received is likely to vary from property to property, and perhaps by time of year.
The reason is because Bostall Hill and Shooters Hill are in the way, which is tree-lined (not good). Couple this with other obstructions such as the school and adjacent four-storey blocks of flats.
If your set has manual tuning then, for ITV/C4/C5 etc scan UHF channel 57 for Woolwich transmitter or UHF channel 26 for Crystal Palace.
If the Woolwich signal is better than the Crystal Palace one then maybe your aerial is pointing to the Woolwich transmitter.
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MikeP: That's interesting because the aerial heights given for PSB channels and COM channels of some of the high-power transmitters are different where they are all at the same power, e.g. Emley Moor. The latter is usually slightly lower down.
I'd read into this that there are two different arrays, perhaps with the latter having the beam tilted lower than the latter. (I note that all six of Winter Hill's are 726m. Sutton Coldfield's are all the same.)
The main transmitters where the COMs run at half power to the PSBs generally have all six muxes at the same height which would suggest that they all use the same array, presumably because the additional cost of a second array isn't seen as worthwhile and that reducing the power is a more economical way of reducing the coverage footprint (so as to reuse the channels).
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sally: A lot of TVs use UHF channel numbers and some use/give frequencies in MHz only - they both relate to the same thing.
In relation to what I said above, Woolwich on C57 is 762MHz. Crystal Palace C26 is 514MHz.
I'm not in the area so can't recommend anyone. The outcome could be that you can only receive the Public Service channels (from Woolwich) - a common question of installers these days being can I change to using a transmitter which carries all channels? As I say, where you are this is at least difficult.
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sally: It sounds like the aerial could be directed to the Woolwich transmitter.
I suggest that you confirm, perhaps in daylight, that it is fitted correctly and hasn't come down.
Also check that there isn't another aerial socket or aerial cable coming into the room - that is check you haven't connected the TV to an old aerial cable that is no longer used.
If there is an aerial wall socket and you therefore use a lead to join the TV to it, can you swap with another to prove that it isn't at fault?
If you have a box such as a recorder, disconnect the box and connect the TV directly to the incoming aerial. That way you discount the box as causing the issue.
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sally: That's correct - UHF is TV.
Confirm, by viewing the signal strength screen, that BBC One is tuned to 786MHz (or could perhaps be 785.8MHz, which is the same thing).
If so, then the TV is tuned to Woolwich transmitter and as such the problem would appear to lie elsewhere (so retuning isn't likely to rectify it).
You will only receive PSB channels which are the BBC, ITV, ITV+1, ITV2, Channel 4, Channel 4+1, E4, Film4, More4 and Channel 5. There is no ITV3, ITV4, Dave, Yesterday etc.
If you are using a booster then remove it.
What do the strength and quality show as on BBC One and ITV? (There isn't a need to check BBC Two because it will be the same as BBC One; likewise Channel 4, Channel 5 etc are the same as ITV.)
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sally: Did you get anything from at800, either at your old address or new one? This could be a postcard or filter which you connect into your aerial lead?
at800 is the company that is run by the 4G mobile operators and is charged with alleviating any issues with TV reception caused by their signals.
I am wondering if this could be caused by one or more 4G base stations. You are around 400m from the telephone exchange whose roof is festooned with mobile phone antennas.
If the issue is 4G signals then at800 will supply you with a free filter to connect inline with your aerial lead. Under such circumstances there may well be nothing wrong with your aerial and therefore any work at your expense would be unnecessary.
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Riv-dogg: That is correct. Mendip's COM7 doesn't come on air until some time in 2014; no date is given by Digital UK.
You may, however, be able to receive Wenvoe's, to some degree, until Mendip's comes on air. Do a manual scan of UHF channel 31 from tomorrow for Wenvoe's.
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Tom Herrington: It's probably worth enquiring with neighbours to see if they have the same issue. See if theirs affects the same channel and comes and goes around the same time as yours.
It sounds rather like a seasonal issue caused by the terrain which the signal path traverses (that's the "line" between the transmitter and you).
Here is a plot of the terrain:
Terrain between ( m a.g.l.) and (antenna m a.g.l.) - Optimising UK DTT Freeview and Radio aerial location
The plotter only samples ground levels at fixed intervals and as it's only just over 2 miles it isn't totally representative. However, it does suggest that the ground between you and Langoed is in the way. Of course, there is also likely to be vegetation on that land which can affect reception.
With this in mind, if you can access it safely, try tilting the aerial up a little if its bracket permits. Failing that, mounting the aerial in a different location such as on the other end of your bungalow might do the trick. That said, because the line-of-sight is interrupted by the terrain you could always be susceptible to such woes.
The thing with digital reception is that it either works or it doesn't - there is very little inbetween where it "sort of" works. Consequently it could be that yours is "only just" not working. It might be that others' signals have degraded but they still have what they would call a "perfect" picture, signals being "only just" good enough. In the days of analogue you would might see the picture get gradually worse.
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Sunday 8 December 2013 6:40PM
Barry: Different frequencies travel differently which explains why all signals broadcast from the same place and at the same power can be received at different levels.
As jb38 says, you could potentially be affected by the "umbrella effect". This is where the high power transmitter focuses the beam further away - which is towards its horizon. This is opposed to focusing on the ground closer to it.
If you can then use the loft aerial. This may provide more stable reception anyway.