All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
Glynn: You are at the side of the transmitter that it is radiating the signal (it isn't omnidirectional), but at only 2W you will almost certainly require line-of-sight to the broadcasting antennas on the transmitter's pole:
mb21 - The Transmission Gallery
I don't know the local area but I imagine that it is weaker (and is predicted as being so on the map) because the terrain is lower which means that the transmitter cannot be seen at the sort of height above ground at which aerials are usually installed.
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Patrick Keeney: I imagine so.
Saorview uses DVB-T signals, even though they carry HD. Freeview uses DVB-T2 only for HD signals. Look in the spec to see if it has a DVB-T2 tuner.
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Debbie: If your receiver allows manual tuning, then do a manual scan of UHF channel 26.
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Neil Robertson: The only other possibility is to try an amplifier.
Not suggesting for one moment that your aerial building skills aren't up to scratch, but you might want to check out A.T.V (Aerials And Television) TV Aerial, DAB Aerial, FM Aerial. for lots of information and an online shop.
I'm not an aerial professional myself, but I have read on here one of the pros saying that in situations where the receiver is quite a bit of having line-of-sight that a lower gain aerial and amplifier can produce better results. The reason being that the acceptance angle of the antenna is greater than a high gain aerial.
Digital signals require good quality and I suppose that a wider "looking" angle means that if part of it isn't so good but others is better then the overall result may be a better quality signal. Whereas focusing on a narrower beam means that should it be poor then the signal received will be poor.
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sass: Emley Moor (Yorkshire) uses lower channels than Winter Hill. Start the automatic tuning scan with the aerial unplugged and plug in about 60%.
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Lorri Henry: Do a manual scan of UHF channel 39. You may need to set it to DVB-T2 mode (rather than DVB-T) if there is such a setting in the manual tune part.
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Eamon: You need to buy a Freeview HD box. See Northern Ireland RTE1, RTE2, TG4 special mini-multiplex from 24 October | ukfree.tv - 10 years of independent, free digital TV advice
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Richard : You need to do some logical "fault"-finding. I say "fault", but it "may" be entirely rectifiable.
Is your aerial directed to Hannington @ 268 degrees, with it set horizontally? If so, confirm that all channels are tuned to Hannington by viewing the signal strength screen when tuned to each:
BBC One = C45
ITV1 = C42
BBC One HD (if applicable) = C39
ITV3 = C41
Pick TV = C44
Film4 = C47
(There are only six multiplexes/signals which carry all the services so there should be no need to check them all - just these six/five will do. They are listed here DTG :: DTT Services by Multiplex )
Having established that the TV/box that you are using for testing is tuned correctly, then connect the feed from the aerial directly to it - that is so it doesn't go via the distribution amplifier ("junction box").
I wonder if the amplifier is set to boost the signal too much (boost it too much now switchover has occurred).
The digital signals prior to switchover were lower than they are now. In particular, the signals radiated by Hannington in your general direction were much lower than in others due to Guildford transmitter using the same channels. Consequently there was a large difference in pre-switchover signal strength versus post-switchover signal strength in your area.
An aerial setup that was installed to pick up the weaker pre-switchover signals may now be too sensitive and providing signals that are OTT. As you have an amplifier, it could be that the feeds from it (to the rooms) are much higher than that going into it. Try turning it down if you can.
The thing with digital reception is that the objective is not to get the strength as near 100% as you can. Providing you have a good *quality* signal, there is a threshold *level* above which it works. Increasing the signal above a safe margin above the threshold will not improve the picture, unlike with analogue. But increase it too high and it is a bit like turning up the volume on a hifi to the point that the sound distorts which is a loss of quality.
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The Commercial (COM) channels (which are on 21, 24 and 27 from Brougher Mountain) don't have as great a coverage area as the (Public Service) PSB channels. The small "filler-in" transmitters don't carry them and of those that do they tend to be on lower power than the PSBs, which is usually half-power. This generally means that those on the fringes can receive PSB only. It certainly does not mean that half of viewers are PSB only!
However, up until now I wasn't aware of a full-service transmitter with such marked differences between power of PSBs and power of COMs. The information provided on this website is taken from official sources and I checked the relevant Ofcom document and it does indeed say that COMs are 2kW from Brougher Mountain whereas PSBs are 20kW.
Add to that the fact that the COMs are each on channels which neighbour the more powerful PSBs and there would appear to be a recipe for some being unable to receive the COMs, not because they aren't powerful on their own, but because the higher power signals will be likely to desensitise receivers to the lower power ones.
To understand this, consider the receiver "looking" at channel 21. Nearby, on C22, is a high power signal which is likely to desensitise it. This is a bit like going out when it's dark and having car headlights shining towards you; as a result the surrounding area that is darker is more difficult to see because your eyes adjust to the bright light by reducing in their sensitivity.
An attenuator put in line with the aerial lead may help. If an amplifier is in use, turning it down or removing it may do the trick. An attenuator simply acts to reduce the signal level which is the opposite of an amplifier so there may be little point in having both.
The only thing I can think is that they are so short of channels that 21, 24 and 27 have to be used. Of course these are used by Divis for its PSBs so there will be overlap of the two transmitters (normally at least), but the Brougher COMs being severly restricted will help mitigate interference with Divis viewers.
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Thursday 25 October 2012 12:07PM
Ron Small: Unless you watch your VHS recorder via the aerial lead (rather than the scart lead) then there is no need to daisy-chain it on the aerial lead as it cannot receive any analogue (I assume).
Thus, if you disconnected it from the aerial lead you wouldn't need to leave it powered on.