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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

Saturday, 23 July 2011

3:45 PM

Mazbar: Jessica was the other box the aerial riggers fitted pluged into the mains. If it was it could be a power suply this has to be pluged in at all times if you unpluged it it will knock all your tv's off check that. Also if your vcr is not a digital one and your tv is just plug the aerial straight into the tv hope this helps.

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Mazbar's 384 posts GB flag
Mazbar's: mapM's Freeview map terrainM's terrain plot wavesM's frequency data M's Freeview Detailed Coverage
8:02 PM

hi guys
My freeview box downstairs is really struggling with a bad signal on 39 (itv, channel 4 etc.). this has started happening over the past couple of weeks.
Upstairs is perfect. I have swapped boxes round and which ever box is plugged in downstairs struggles.
There are no other games consoles etc plugged in and we have not had any new appliances etc which could be causing interference.
Any idea what we should try now? Should we replace aerial lead, get booster?

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Susan's 1 post GB flag

8:44 PM

Susan: This indicates that the signal is getting degraded by the extra cable length involved going downstairs, you should use a two way powered splitter upstairs with the aerial lead going directly into it, these available from various sources including Argos.

You then use the splitters first outlet position for the upstairs TV, and with the second outlet feeding the down stairs TV, results being virtually guaranteed if you use this system, this based on what you report is happening.

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jb38's 7,179 posts GB flag
Tuesday, 26 July 2011
4:28 PM

Hi Folks,

Interesting site, congratulations to all who work on it and give advice.
Hopefully you lot can help me out with the problem that I have receiving Freeview channels. I live in Swansea and about 10 days ago I could receive probably 30+ TV & radio channels but for no known reason my reception has gone down to 10 TV channels (not my favourites either) & zero radio channels. All the BBC channels have disappeared along with the numerous others. Why am I unable to receive the 30+ TV & radio channels I had before, when the 10 I do receive are picture & sound perfect? Am I right in assuming that the aerial is working if I'm receiving 10 TV channels? I've tested the Freeview box at a neighbours house on his television and it worked perfectly (70+ TV channels and numerous radio channels). How can I solve this problem? Thanks in advance Andy.

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Andy's 1 post GB flag
Wednesday, 27 July 2011
Wednesday, 10 August 2011
dan waterfield
8:05 PM

Hello Braintist.

I am a tvsat engineer and install irs systems in blocks of appartments. i live near bradford but do a few installations around newcastle. about 3 years ago i installed a system at bishop awkland for 36 flats and 16 bungalows. the aerial signal wasnt great but after amplification it was ok. i have signal power records and carrier to noise records and although some multiplexes were weaker than othersin both power and carrier to noise, it was only by 8db.{power}. i tested every tv and satellite point in flats via a promax explora analizer. we have had no complaints for 3 years but recently another tv engineer has been to check the system and says it has been installed wrong and the equipment used is wrong. the main reason for my txt is he is saying there is a masive difference in signal from each multiplex to the flats. I have just installed a system today in darlington and noticed a 20db difference in frequency 21 and frequency 42. i used a log periodic which is meant to balance the signals a bit better than a high gain aerial. i was in a great reception area to bilsdale transitter but still had this variation. viewing my signal records from 3 years ago this variation didnt seem so severe and just wondered if any work has been done or adjustments have happened to the bilsdale transmitter as i have been installing these type of systems for 12 years and am fairly gutted about him saying its all wrong. any help would be greatful.

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dan waterfield's 1 post GB flag
Monday, 15 August 2011
dan preston
4:31 PM


I have a Humax PVR 9200T and live at HP4 3LE.

Recently I re-scanned all my channels which has resulted in the BBC channels being unwatchable due to picture/sound break up (the box re-scanned this multiplex of Channels to "Channel 27" and says Cambs & Bed as the TV transmitter). All the other channels are completely unaffected and interestingly all say "London" as the TV transmitter location.
Why is it sourcing 2 different TV transmitters especially since one of them has a rubbish signal?

Is there a way to point or manually tune these BBC channels towards the London transmitter. I had a look at the manual tuning dialogue page but it was not very intuactive and I was unable to solve the problem.

Many thanks in advance.


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dan preston's 2 posts GB flag
dan's: mapD's Freeview map terrainD's terrain plot wavesD's frequency data D's Freeview Detailed Coverage
Thursday, 18 August 2011

9:45 AM

dan preston: If your aerial is pointing at more than one transmitter, your box will try to use them both. Crystal Palace is directly in line with the Hemel Hempstead transmitter from your location.

Yes, you can clear all the channels and add the six multiplexes in manually: the channels are listed on the Freeview on Crystal Palace TV transmitter | - independent free digital TV advice page.

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Briantist's 38,908 posts GB flag
11:00 PM

I am on the rosneath transmitter. reception is OK all channels except BBC. i have a sagem set top box . after a few minutes of watching TV the set switches channels to another BBC channel often the previous one watched though i suspect it May be a random process.

also i have a philips dvd recorder and set top box combined which loses all channels on power-off. philips can offer no solution.

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bRIAN RAWLINSON's 6 posts GB flag
Friday, 19 August 2011
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