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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
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I have been told I would receive too much singal from my Freeview tansmitter as 3
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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
High pressure causing channel loss through "Inversion"3
Digital Region Overlap4
Freeview reception has changed?5
Two frequency interference 6

Monday, 14 February 2011
3:15 PM

Hi jb38,
Yes the cable is fed by a booster that is next to the wall socket.
The wall socket is connected directly to the aerial.
The wall socket is not connected to the sky box. It used to be, but i removed it all to eliminate problems and boost the signal.
When the booster is off the TV upstairs can still view freeview. Analogue picture is terrible all the time.

I tried changing the HDMI cables and tried a scart lead. Still had the problem. I think it could be the TV as the source. Or it could be linked to the following.....
We had a loft conversion a couple of years ago, the aerial had to go on the roof and the electrician, messed up the cabling (some how not sure on details). After we had the new aerial installed there was no signal so guy came back and said we need a booster and it worked after that.
There is another TV upstairs (freeview) which has a direct feed from the aerial and that is fine.
I think it may be best to have another feed from the aerial put in rather than an extension or buy a surge protector for tv interference?

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rob's 6 posts GB flag
Tuesday, 15 February 2011
1:30 PM

My grandparents are having problems receiving Multiplex 1. They have a new Samasung TV with Freeview built in and all the other channels are fine but on Multiplex 1 the BER flickers 30% - 80% and the signal strength flickers between 0% and 25%. This results in a the picture and sound freezing or breaking up.

I recently bought a Sony TV which I brought round and tested. On this TV which also has freeview built in Multiplex 1 works fine and the signal strength is consistently above 75%.

Please can you advise on the best way forward. I have tried re-tuneing the Samsung telly but the problem remains.

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4d's 4 posts GB flag

1:51 PM

4d: I would have a look at Freeview intermittent interference | - independent free digital TV advice for some things to look for.

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Briantist's 38,910 posts GB flag
Yunglen in Lincs
2:40 PM

We are at DN40 3AW. Until today we have had a very good recepttion of all the FV channels. Today. 15/02/2011, 1400hrs we have lost all th MX D Channels and also ITV3. Is the changeover work causing this and affecting signal strength on different days before the digital switchover?

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Yunglen in Lincs's 2 posts GB flag
Yunglen's: mapY's Freeview map terrainY's terrain plot wavesY's frequency data Y's Freeview Detailed Coverage

2:51 PM

Yunglen in Lincs: There is no work at Belmont, and no faults are reported. Can you see the Freeview reception has changed? | - independent free digital TV advice page?

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Briantist's 38,910 posts GB flag
Wednesday, 16 February 2011
5:16 PM

I have tried switchin off every appliance in the house but to no avail. I find it odd that the reception is fine on another television. That would suggest it is the reciever in the TV which is having problems.

But then the fact that all the other channels other than the BBC range are working fine makes me wonder if it can be the TV>

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4d's 4 posts GB flag
4d's: map4's Freeview map terrain4's terrain plot waves4's frequency data 4's Freeview Detailed Coverage

6:44 PM

4d: Just to check, are you using exactly the same cables too?

I'm not sure if you shouldn't just wait for the new high power service on 30th March 2011.

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Briantist's 38,910 posts GB flag
Thursday, 17 February 2011
2:12 PM

Yes everything is exactly the same except the TV. I am wandering if it is likely to be a fault with the freeeview receiver within the Samasung telly. If so I need to return it before the warranty expires at the end of the month.

But if the other channels are all working fine would this suggest the TV is not the problem?

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4d's 4 posts GB flag
4d's: map4's Freeview map terrain4's terrain plot waves4's frequency data 4's Freeview Detailed Coverage

2:38 PM

4d: It could just be a sensitivity threshold problem - which will go away on 30th March as your signals will be much stronger then.

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Briantist's 38,910 posts GB flag
Tuesday, 22 February 2011
7:11 PM
Great Missenden

I live in hp16 oeu. we have 3 TV's , 2 with set box Freeview boxes and one with a built in Freeview tuner. about 3 weeks ago we suddenly lost bb4 on all 3 TV's with pixelation/no picture. i have since found the same problem with channel 301 and BBC parliament implying loss of multplex b. we have no sky boxes,pvr's or games consuls. we have 2 VCR's. one TV is just itself plus a set top box. if the other TV's and VCR's are switched off this TV still can't get any of the multiplex b channels. we have a masthead amplifier on the aerial and are 1 mile from the great missenden transmitter to which i assume the aerial is directed.

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JOHN NEWMAN's 1 post GB flag
JOHN's: ...
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