My ITV/C4 Freeview channels have disappeared - what can I do? Is it my SCART ca
Brian Butterworth published on UK Free TV It is a feature of television signals that they can be effected by the weather. Aside from the obvious damaged that can be caused by wind or torrential rain, the onset of summer can cause a more intriguing problem called "inversion".
Basically, when the sun heats up the land, the hot air can get trapped below cold air at high level. This creates an "inversion layer" which acts like a polished mirror to TV signals. This causes two problems: you can receive both the original and a reflected signal from your own transmitter (on analogue TV this appears as "ghosting") or interference from TV transmitters that are normally too far distant.
The ITV/C4 multiplex of channels (ITV-1, ITV-2, ITV-3, ITV-4, CITV, C4, More4, E4, Quizcall) use a transmission "mode" called 64QAM, and it is sadly much more prone to these problems.
So, whilst a loft-mounted aerial will provide reception at some time, it will fail at others. The only real solution is to mount the aerial (or a new Class I aerial) outside on a pole, but some people report that changing the cable from the aerial to the set-top box to the high-grade satellite cable can also help.
The SCART connection, by the way, only carries a single TV picture, not the Freeview transmission multiplexes, so if this is disconnected it will result in degradation to every channel at once.
All questions
In this section
Thursday, 28 June 2012
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Mark Fletcher12:42 AM
Lytham St. Annes
Rob Alka.I would up both Single Frequency Interference as well as Inversion Effect as possible causes.
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Mark's: mapM's Freeview map terrainM's terrain plot wavesM's frequency data M's Freeview Detailed Coverage
Friday, 29 June 2012
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Mike S8:27 AM
Uckfield
We have four TV's,are located in TN22 2AY and receive from Heathfield. All re-tunes have been done.Panasonic in the lounge,fed by a Humax and a Polaroid in the kitchen will not pick up channel 10. Two bedroom units,both Venturer are ok. Labgear signal finder gives 50dB at source. Splitter unit used to distribute. Lounge cable via Humax gives 60dB all others 50dB.
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Mike's: mapM's Freeview map terrainM's terrain plot wavesM's frequency data M's Freeview Detailed Coverage
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Louise7:54 PM
Loughborough
Hi, we've never had any problems with reception on any stations until this week. Suddenly all we can get is the BBC channels, all the ITV, CH4,5 etc start off as blank with no sound or picture and later in the evening start to clear up with intermittent sound and picture then end up OK at around 10pm. We're on the Waltham transmiter. Is there a reason why we've suddenly lost the signal? Is there any way to get it back? Thanks
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Louise's: mapL's Freeview map terrainL's terrain plot wavesL's frequency data L's Freeview Detailed Coverage
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paul8:08 PM
Ipswich
retuned on the 27th as told, got over 80 channels, following day lots of channels either gone or broken up, retuned again got over 80 channels, this evening lots of channels missing, retuned channels still mising, any ideas ? We ar in Ipswich, I believe on the sudbury transmitter.
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paul's: mapP's Freeview map terrainP's terrain plot wavesP's frequency data P's Freeview Detailed Coverage
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KMJ,Derby9:21 PM
paul: If retuning restores channels which are broken up or missing, it suggests that possibly you are receiving signals from more than one transmitter. Does your receiver do an automatic retune each night? If so this facility should be turned off if possible, after tuning into the correct set of frequencies for the Sudbury transmitter. You do not say which muxes are giving problems. The PSB muxes are possibly being received additionally from Bramford which is in the same direction as Sudbury, but transmit with vertical polarisation. If it is the COM muxes that are giving problems, these are also predicted to be receivable from Tacolneston at your location. When doing a scan for channels try to note which frequencies are being stored when you have correct working channels, then if possible check which frequencies are being received when the channels are breaking up. I should also mention that in the (less likely) event that Bramford or Tacolneston signals give good reception whilst Sudbury gives breaking up reception this would indicate Sudbury to be delivering too much signal.
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Saturday, 30 June 2012
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agmac10:09 AM
Glasgow
samsung lcd series 5 no itv ch4 ch5 tried all retuning options without success.
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agmac's: mapA's Freeview map terrainA's terrain plot wavesA's frequency data A's Freeview Detailed Coverage
Sunday, 1 July 2012
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Jim9:27 AM
I have just bought the latest humax. Tuned it in and I can't get itv4! I live at ST13 and annoying my relatives at st9 can get it. Anything I can do?
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Jim: The Commercial (COM) services, which include ITV4, don't have as wide a reach as the Public Service Broadcaster (PSB) ones.
The COMs transmit from 81 of the largest sites (largest by viewer population) and reach 90% of the population. There are over 1,000 small "filler-in" relays which carry only PSB channels because the COMs do not wish to invest in them. These cover 8.5% of the population.
The cost to the COMs to broadcast from these other sites is about the same as what it costs them for the ones they have now. As there objective is profit from selling advertising which they show to as many viewers as possible at lowest possible cost, then it's not surprising why they don't want to broadcast from the other sites. They don't have any "Public Service" obligation.
You've said that you reside in ST13 which is a big place and doesn't give any absolute indication of which transmitter you are receiving from. Indeed, provision of a full post code doesn't either, although it might narrow down the possibilities.
I do note that it is the area of Leek and that it has one of the PSB-only relay transmitters, so I wonder if you are receiving from it, hence why you are not picking up the COMs.
For a full list of services, see here:
DMOL Post-DSO Multiplex Channel Allocations
As shown, there are three PSB multiplexes (PSB3 is the HD one) and three COMs ones.
If you are using the Leek transmitter, then in order to see if you can ever receive the COMs terrestrial channels, then you need to investigate the possibility of receiving from one of the transmitters that carries them, such as Sutton Coldfield.
If you can't, then you will have to look at some other platform to receive additional channels. Freesat is a common alternative, particularly in areas where the Freeview COMs aren't available. There are some differences between full Freeview and Freesat. For example, Dave and Yesterday are not available on Freesat and this is probably because they are on Sky's subscription service. This does, of course, require a different box.
If you provide your location, preferably in the form of post code, we may be able to assess the likelihood/degree of difficulty you may have in trying to pick up the COMs.
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Mik7:41 PM
Folkestone
Signal keeps breaking up on bt vision box, goodmans digi box, works fine with cheap box from tesco. Aerial on roof pointing to Dover from ct188en. Live in a bungalow but aerial up high on a pole. Frustrating as have 3 goodmans box's in bedrooms. Any ideas?!
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Mik's: mapM's Freeview map terrainM's terrain plot wavesM's frequency data M's Freeview Detailed Coverage
Mik: The problem could be that, having carried out its scan of frequencies, the BT Vision box has decided to go with the signals from the Lyminge relay transmitter. This only carries the Public Service Broadcaster (PSB) services which are BBC, ITV1, ITV1+1, ITV2, Channel 4, Channel 4+1, E4, More 4, Channel 5 and the four HD services.
See if you can find out whether this is the case or not. I'm not familiar with the BT Vision box, but usually receivers give the UHF channel number (frequency) that they are tuned to on the signal strength screen.
BBC One should be tuned to C50 (for Dover) and not C22 (Lyminge). Similarly, ITV1 should be C51 and not C25.
If either of these are not tuned to Dover, then run the automatic tuning scan with the aerial unplugged up until 40% of the scan. This will miss out scanning of the frequencies used by the unwanted transmitter.
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