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Freeview intermittent interference

When you get occasional sound loss or picture freezes

When you get occasional sound loss or picture freezes
published on UK Free TV

There are several different types of interference that cause problems. This page deals with the situation where:

  • Freeview reception is perfect or near-perfect most of the time
  • The audio on TV and radio channels mutes momentarily a few times each minute
  • The picture on a Freeview channel freezes a few times each minute

There are two main causes of this type of intermittent interference:
  • 'Induction' interference
  • Mobile phone interference

Induction interference

Induction interference is caused by mains-powered household devices that contain a large motor, such as:
  • Washing machine;
  • Tumble dryer;
  • Central heating pump or combination boiler;
  • Fridge;
  • Freezer;
  • Power tools (drills, jigsaws etc)
  • Vacuum cleaners;
  • Water pumps;
  • Automatic doors

You can identify if one or more of these devices is causing the Freeview reception problem by powering off the devices.

If one of these devices is causing the problem, then the reception problem can usually be solved by using a mains filter device and use it on the Freeview boxes mains connection.

Such as device is this: Maplin: 6-Way Flat Screen and HDTV Surge Protector and Mains Filter.

Mobile phone interference

If you keep a mobile phone by your Freeview box or digital television, keep it further away!

This also applies to other transmitters such as baby monitors, video senders, walkie talkies, and portable phones.

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In this section
Official aerial installers guide to the TV spectrum future1
Which free digital TV system will give me the most reliable reception?2
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Saturday, 7 January 2012

7:09 PM

Ann: If you had problem free reception prior to switchover there are usually two possible reasons for the same installation suddenly giving trouble when the transmitter powers are increased. Firstly, when scanning for channels, the tuner finds signals from a different transmitter to that to which the aerial is pointing, it then stores channels for weak or erratic signals. When the correct signals are found the extra channels are either stored in the 800s of the channel list or ignored completely as duplicates. If this is found to be the case manual tuning of the correct set of frequencies, after first clearing the channel list, usually restores correct working. The second problem is the use of very high gain aerials or amplifiers which might have been needed in order to receive the low power signals before switchover. When the high power working began the signals were then too strong, producing similar effects to weak signals. in this case amplifiers need to be removed or gain turned down, or an attenuator fitted in the aerial feed to restore correct reception.

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KMJ,Derby's 1,811 posts GB flag
Dave Lindsay

7:39 PM

Ann: I would do as KMJ,Derby says, and confirm that the channels are tuned correctly. That is that you are tuned to Emley Moor for all channels and not another transmitter for some or all.

For each of the following programme channels, go through the menu to the signal strength/quality screen and see what UHF channel (frequency) they are tuned to. The channel numbers I've given are those of Emley Moor:

BBC One = Ch47
ITV1 = Ch44
BBC One HD = Ch41 (only applicable if you have a HD TV/box)
ITV3 = Ch51
Pick TV = Ch52
Yesterday = Ch48

If all these are as shown, then your TV is tuned to Emley Moor and I would be looking at fitting an attenuator (and removing any booster/amplifier).

If they are not as shown, then that suggests that the problem is that signals are being picked up from another transmitter. The most likely one in your area is Belmont (Lincolnshire) and its six channels are 22, 25, 28, 30, 53, 60. You might have found that one or more of the above programme channels are tuned to these. E.g. if you go to ITV1 and look on the signal strength screen and it says that it is tuned to Ch28, then it is picking up the signal from Belmont instead of Emley Moor.

If your TV is tuned to Belmont, then the easiest way to prevent this is to have the aerial unplugged for the first 25% of the scan (or whilst it gets past Ch30 if it gives channel numbers).

If you would like further help with this, then please post the make and model of your TV and I will see if I can find the user manual on the internet so as to tell you how to proceed.

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Dave Lindsay's 5,724 posts GB flag
Sunday, 8 January 2012
4:50 PM

We have just installed a new digital tv with free view after tuning we only have 18 channels and only the BBC channels work, ITV Channel 4/5 and all others have a pixelated picture and inteference , any suggestions please? Our postcode is sn6 6pm.

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Mandy's 2 posts GB flag
Mandy's: mapM's Freeview map terrainM's terrain plot wavesM's frequency data M's Freeview Detailed Coverage
Dave Lindsay

6:12 PM

Mandy: What direction is your aerial pointing? Is it horizontal or vertical?

If it is pointing to either Oxford or Mendip transmitters, then the commercial channels are on low power for a few months.

Pixelated ITV1, C4, C5 could be as a result of it tuning to the wrong transmitter.

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Dave Lindsay's 5,724 posts GB flag

6:29 PM

Mandy: Which transmitter is your aerial pointing to? Mendip is SW with aerial rods horizontal, Oxford is ENE with rods horizontal and Cirencester relay is NNW with rods vertical. It is likely that you have tuned in to the wrong transmitter, at least as far as Mux D3+4 (ITV1&2, C4, C5 etc) is concerned. Check if there is an ITV1 that works in the 800s of the channel list. This could also be the case with the COM muxes, although it should be noted that these muxes are transmitting at reduced power at both Mendip and Oxford. If you are tuned to the wrong frequencies clear the channel list, then if possible do a manual tune for the correct set of frequencies. Insert C53, C60, C62, C59, C55 (and C57(HD) if required). For Mendip use C61, C54, C48, C67, C52 and C58(HD). Less likely is Cirencester which only transmits the PSB muxes on C23, C29 and C26 for HD.

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KMJ,Derby's 1,811 posts GB flag
7:05 PM

Our aerial is horizontal and pretty sure it is pointing to Oxford, our other digital tv upstairs receives the other ITV and additional channels with a great picture albeit not with the full freeview channels. I will try manual tuning, thank you KMJ,Derby and Dave for your help.

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Mandy's 2 posts GB flag
Dave Lindsay

7:40 PM

Mandy: If you manually tune, you will probably need to wipe the memory. This is because if it has already stored a particular multiplex (in the 800s), then it might not do what you want which is to move them into their proper logical channel numbers.

I would check to see that they are all tuned as they should be, and only resort to retuning if there is one that isn't correct.

For each one, go to the channel in question and then go to the signal strength/quality screen and it will tell you the UHF channel that it is tuned to.

You should only need to do the following five (or six for HD) because each UHF channel carries a number of services.

BBC One = Ch53
ITV1 = Ch60
BBC One HD = Ch57
ITV3 = Ch62
Pick TV = Ch59
Yesterday = Ch55

62, 59 and 55 are on low power until 18th April.

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Dave Lindsay's 5,724 posts GB flag
Wednesday, 11 January 2012
Carol Stanwell
8:34 PM

My humax freeview digibox has been freezing up on Wednesdays for the last 5 weeks. Get a good picture but can't use the channel changer, none of the controls wok, volume for instance. Does free up if turn off on back of box and back on again. Get about 30 sec to change channels. Any ideas. Tried all the unplugging, replugging, checking connections. Any ideas. Postcode BS27 3BS

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Carol Stanwell's 2 posts GB flag
Carol's: mapC's Freeview map terrainC's terrain plot wavesC's frequency data C's Freeview Detailed Coverage
Thursday, 12 January 2012
Peter Henderson
11:01 AM

I am getting the same problem as Carol Stanwell in that my JVC HT-32DE9BJ LCD PVR freezes up on Wednesdays. When I first turn on I have about 2 minutes to select the desired channel and select anything else I want to set before only the desired program runs. To change to another a channel, I have to shut round and start again. The whole thing then returns to normal at about midday on Thursday.

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Peter Henderson's 1 post GB flag
Dave Lindsay

11:14 AM

Peter Henderson: Your model is on the list of downloads:

DTG :: DTT Receiver Downloads

I wonder if the two events are connected....

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Dave Lindsay's 5,724 posts GB flag
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