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Single frequency interference

What to do when several channels are missing, but they are all on the same 'multiplex'

What to do when several channels are missing, but they are all
published on UK Free TV

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

There are two main causes of this type of intermitted interference: The current Freeview mulitplexes are shown in this diagram. If all of your missing channels are on a single row, you have "single frequency interference":

Local analogue interference

Local analogue interference is caused by household video devices that you can attach to a television such as:
  • Sky Digibox;
  • Video cassette recorder (VCR);
  • Personal digital video recorder (PVR);
  • Games console;
If you have any of these devices, you will need to work out which of these is blocking the reception of a Freeview multiplex by turning off the suspect device and then rescanning for channels on the Freeview box.

If powering off the device restores the Freeview channels from the blocked multiplex, you will need to either stop using the problem device's RF output by disconnecting the RF output cable permanently, or by changing the RF channel number that that device uses. See, for example, How do I change the RF output channel on a Sky Digibox?

You can find a list of the frequencies that are not in use at your location by putting your postcode into the My Freeview reception and looking under the "Free RF channels" section.

Non-wideband aerial in some areas

In some places you will need a wideband aerial to receive all the Freeview multiplexes. For example in Central Birmingham, the Sutton Coldfield has multiplex D on an 'out of group', so you cannot view Film4 or ITV2+1 without an aerial upgrade.

To find out if you need an aerial upgrade, see My Freeview reception.

Help with Freeview, aerials?
How do I get a test card with Freeview1
I would like to know if it is possible to receive UK terrestrial Freeview servic2
I have been told I would receive too much singal from my Freeview tansmitter as 3
Can my Freeview box receive more than one BBC and ITV region?4
Is it true that my 87 year old mother is entitled to a FREE upgrade when the ana5
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
High pressure causing channel loss through "Inversion"3
Digital Region Overlap4
Freeview reception has changed?5
Two frequency interference 6

Friday, 17 February 2012
Doug Robinson
10:24 AM

I use a Digitalstream Freeview+ recorder.

My signal on SD multiplexes is about 50% strength, and 95-100% quality. On HD it's about 48% strength and the same on quality.

Except yesterday on mux C (Dave etc), it dropped to 50% strength and 1% quality. Until then it was the same as the others.

I receive signals from Emley Moor, and live in Doncaster.

The TV receives all channels fine.
DS issued me with an update when it happened before which worked. But is this likely to keep happening?

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Doug Robinson's 1 post GB flag
Wednesday, 22 February 2012
Frank Smith
7:54 PM

I lost film 4, yesterday and several other channels when the multiplex carrying them changed to a frequency not received by my old aerial > this was the reason given when I asked why it happened.
Since then I have installed a new Televes 45 aerial re cabled my system and checked all connections.
The situation is now the signal strength and quality are excellent except for the ones mentioned above, these I receive but quite often they break up and display the logo no signal
What else can I do to restore these channels to a watchable condition.

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Frank Smith's 8 posts GB flag
Tuesday, 13 March 2012
9:29 PM

Hi. Just got a freeview box and set it up, been using broadband up till now, but that has got so bad, decided to go back to the old ways. I get a Welsh version of ITV4, is there a way to get the English version? I guess I am receiving from Merthyr as my loft aerial is pointing WNN (Not really Merthyr direction but close). I am also missing Dave. To be honest I have no idea of what I am doing so any help would be appreciated. CF45 postcode area.

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Chris's 2 posts GB flag
Wednesday, 14 March 2012
Dave Lindsay

11:15 AM

Chris: There are quite a few areas of Wales where the Commercial (COM) channels such as Dave will never reach. Due to the terrain, there are many small transmitters that the Commercial operators aren't bothered with.

Merthyr is one such example; it is a Freeview Light transmitter, only carrying the Public Service Broadcaster (PSB) channels.

See Freeview multiplexes | - independent free digital TV advice for a list of all the multiplexes. The PSBs are BBCA, BBCB and D3&4. The COMs are SDN, ArqA and ArqB.

ITV4 is COM and I am not aware that there is a Welsh version. Are you referring to S4C? If so, in Wales S4C is on logical channel number (LCN) number 4 and Channel 4 is on LCN8.

If you provide a full post code, a more accurate prediction of the likely possibilities can be made. Aberdare transmitter is a full Freeview transmitter (it carries PSBs and COMs). It also requires aerials to be vertical.

Looking at your neighbours' aerials will also yield clues.

For Merthyr Tydfil transmitter, your aerial should be vertical.

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Dave Lindsay's 5,724 posts GB flag
Friday, 16 March 2012
9:08 PM
Mountain Ash

Thanks Dave for your quick and helpful reply.

As I said I have so little idea what all this means,but your reply has given me some understanding.

If there is a transmitter at Aberdare, that would be the direction my aerial points. Looking at other aerials, mine is similarly aligned. I thought it was a bit off for Merthyr.

ITV4 (That's the same as Channel4? The Professionals.Shows my age!) is what I mean, sorry for idiocy on my part, I haven't watched UK TV for 5 or 6 years, and then it was on the South coast, no digital just point an aerial and see what happens!

So looks like you have sorted all my problems. Thanks.

CF45 4AZ, I had to put that into my box, I did wonder if I should have used my old postcode, would that have made any difference had I done so?

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Chris's 2 posts GB flag
Chris's: mapC's Freeview map terrainC's terrain plot wavesC's frequency data C's Freeview Detailed Coverage
Saturday, 17 March 2012
10:40 AM

Briantest: I have single frequency interference as you have diagnosed. It only started 16/3/2012 and your row No.2 is the multiplex that has been effected. I can not find anyway to solve this. Can you assist

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Geoff's 1 post GB flag
Geoff's: mapG's Freeview map terrainG's terrain plot wavesG's frequency data G's Freeview Detailed Coverage
Dave Lindsay

12:54 PM

Chris: ITV4 isn't the same as Channel 4. I think a little potted history lesson is necessary.

In 1955, "ITV" started up, which is a group of regional operators such as Granada, Meridian, Yorkshire etc. Over the years, the regional operators have been bought and now those in England and Wales are all owned by the same company, ITV Plc. Today it uses the "ITV1" wallpaper for its network of regional stations. I'll come on to why the "1" has been added.

In 1982, the fourth television service was launched in the UK. For everywhere except Wales, it was Channel 4. Wales got its own fourth service, S4C.

The introduction of the digital system ("Freeview") means that more channels can be broadcast. This has lead to the BBC, ITV Plc, Channel 4 and others introducing other channels.

The BBC started up BBC Three and BBC Four, ITV Plc has ITV2, ITV3 and ITV4 and Channel 4 has E4, More 4, 4Music and Film4. The "1" on ITV has been introduced due to the other three ITV Plc services being in operation.

Because the Freeview system can carry more channels, Channel 4 can now be broadcast Wales, as well as S4C. Because button number 4 is used in Wales by S4C, Channel 4 is on button 8 in Wales.

The transmitter called "Aberdare" is on the hill to the east of Cwmbach. See here for a map of the location:

Bing Maps - Driving Directions, Traffic and Road Conditions

And here for photographs:

mb21 - The Transmission Gallery

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Dave Lindsay's 5,724 posts GB flag
Monday, 19 March 2012
6:43 AM

Switched on my TV with integral digital receiver this morning and it says it cant find a signal. Have returned with and without arial connection, still nothing. Was working fine last night, no power cuts over night.

I'm in Cheltenham - any ideas?

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Silva's 1 post GB flag
Wednesday, 4 April 2012
chris sparks
3:00 PM

Still no HD channels today after switchover reset/retune and none for the last few months. Gravesend DA110LR postcode seems to be a deadzone at the moment. Will all be well on 18th ?

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chris sparks's 1 post GB flag
chris's: mapC's Freeview map terrainC's terrain plot wavesC's frequency data C's Freeview Detailed Coverage

4:40 PM

chris sparks: Nothing really took place during this first stage of switchover that involved the HD service hence you not having noticed any changes, but its almost a foregone conclusion that you will have good HD reception come April 18th, and with the signal received being at a similar level to that of BBC1 that's already operating on high power.

By the way the HD mux will also have changed its operating channel on the 18th from the present of Ch31 down to Ch30.

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jb38's 7,179 posts GB flag
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