All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
Rob: I bow to jb38's judgement here as he is the professional and I'm not, but the Group A gain curves published by ATV suggest that C37 may have a higher gain than C21:
Gain (curves), Again
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Carol, Glasgow: If the booster is for one room only then it might not be needed following switchover.
If it is required then contact at800:
Contact at800 / DMSL | General Enquiries | at800
I was wondering this one myself. The threaded connectors are f-connectors and are used for more perminant connections, i.e. generally not behind the TV set.
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Debbie : There is transmitter work on-going so it could be on low power which, evidently, isn't powerful enough for your set-up.
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toni bussola: It would have been useful if you had said which transmitter you are using because it affects the answer!
At your location Bilsdale is good; this carries BBC North East & Cumbria and ITV Tyne Tees. Emley Moor - which carries BBC Yorkshire and ITV Yorkshire - may also be available, and indeed looking on Streetview I can see some aerials pointing to it.
I shall assume you are receiving from Bilsdale. In which case if you have not replaced your aerial from the days of four-channel analogue then it may be a Group A one. This means that it is most sensitive (i.e. is best at "hearing") at Group A frequencies which are the first third of those used for TV. Sensitivity slopes downwards outside of Group A (outside being higher frequencies/channels).
Unfortunately the Commercial (COM) channels from Bilsdale are outside of Group A; they are in Group B which is the middle third of the band. Consequently Group A aerials may be found not to be sensitive enough on those higher channels (frequencies).
The highest channel, and therefore the one furthest away from Group A is C46 which is for COM5 multiplex which carries Pick TV, Dave, Really, E4+1 and others. See here for a full list:
DTG :: DTT Services by Multiplex
For digital reception a receiver requires the incoming signal to be above a particular level - its lower threshold - in order to resolve a picture. Signal levels vary slightly due to the weather and so on. Therefore in order to have reliable reception, the signal level needs to be sufficiently above that threshold such that a slight reduction doesn't put it below. Perhaps your difficulty is that your aerial isn't sensitive enough (as it's a Group A one) to do this, it only providing a signal over the threshold at times when it is a bit stronger.
As such, retuning is a total waste of time. This is not a fault with your receiver 'forgetting' what has been stored and what is being broadcast is not changing such that a retune is required.
If you have a receiver which has a manual tuning function then go to it and select/enter UHF channel 46 but don't press the button to scan/add channels as at this point a receiver often works as signal meter, giving strength and quality, even if the former is under the threshold required (which is what you want). Compare this with C43 (COM4 - ITV3 etc) and C40 (COM6 - Film4 etc) and note down the values. When it goes again (or when it comes back) do the same and you might find the strength has increased.
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Nick: A red stopper means they are Group A aerials. Crystal Palace uses Group A channels exclusively, even after switchover, so there is no need to replace them because they are the wrong group:
Aerials, TV Aerial and Digital Aerial
According to Digital UK, Crystal Palace is on a bearing of 82 degrees. I presume this is relative to either True North or Grid North. Magnetic North moves over time.
You may be in an area where 4G at 800MHz testing was taking place:
at800 West London 4G tests
According to what we know on this site there are base stations on Hampton Court Way for the four mobile network operators. On Streetview they can quite clearly be seen, all to the south of the river: two by the railway line and not far back from the river bank and three a few tens of metres away on on the grass verges.
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Nick: You say there are two aerials feeding four points. How do the feeds split? Does each aerial feed two points?
If there is a powered splitter (distribution amplifier) involved then it might be that you can do away with it because the TV signals are so strong now switchover has taken place.
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M.Gibson: The symptoms would seem to suggest some local interference. In cases where the start and end times are always the same then a device that is electronically timed may be the cause.
If you are interested in resolving the issue then it might be worthwhile making enquiries with neighbours, to see if their Freeview reception is affected in the same or similar manner. I emphasise that this probably won't be affecting those who view TV via satellite (Freesat/Sky).
Payment of the TV Licence permits television receivers to be used in the applicable property. It does not give any guarantees of reception, nor does it provide for assistance resolving reception issues.
On this site we look to offer help to work to resolve issues. Speak to your neighbours and see what they say. You can always come back here with your findings and we may be able to make some suggestions as to how to proceed.
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Nick: Whilst it is always good practice to check that the TV or box is tuned to the correct transmitter (and that you aren't trying to affect better reception with the aerial pointing the wrong way), based on the prediction of what might be available it does seem doubtful that this may be so.
Nonetheless, confirm by viewing the tuned UHF channel on the signal strength screen while on each of the following:
PSB1 | BBC One = C23
PSB2 | ITV = C26
PSB3 | BBC One HD = C30
COM4 | ITV3 = C25
COM5 | Pick TV = C22
COM6 | Film4 = C28
For a full list of service by multiplex (mux), see:
DTG :: DTT Services by Multiplex
Having checked one service from each mux, the rest "should" be the same.
The COM channels use a signal mode that is less rugged than PSB1 and PSB2. This is so they can get more services in (more shopping channels!) and it comes at the expense of making them more fragile.
Consequently, the direction of the aerial will probably be more critical for them. I am not an aerial installer but I know this from my own experience. Whilst all five standard definition muxes are radiated at the same power from my transmitter, which is Emley Moor, on turning the aerial off-beam the COMs are lost but the PSBs are still strong. I guess that as Crystal Palace also has all muxes at the same power (not all do) then a similar situation may exist.
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Moira Davidson: If you have one aerial which feeds the lounge and the bedroom (and maybe other rooms) then how is this distributed?
If it is a powered amplifier (booster) which it may well be then try turning of the mains supply to it and see if the weak signal drops further. Do this by bringing up the signal strength screen and observing the value then switch off the amplifier. If it doesn't drop then the amplifier isn't doing its job and either it or its power supply is faulty. The fact that the power indicator is illuminated on the amplifier and/or amp's power supply doesn't mean that it is functioning normally.
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Sunday 14 July 2013 3:27PM
Vince Mathieson: See:
UTV DAB | Welcome to UTV Digital Radio Multiplexes