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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
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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

Friday, 3 January 2014
Dave Lindsay

11:40 PM

Silvio: Where abouts are you? Are you using a communal aerial system?

C33 is on lower power than the rest, so some Crystal Palace users won't be able to pick it up reliably. The power in itself is in no way "low", it being 36.3kW.

When manually scanning, set it to DVB-T2 rather than DVB-T, if there is such an option.

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Dave Lindsay's 5,724 posts GB
Saturday, 4 January 2014
8:56 PM

Hi, since connecting my talk talk freeview box to my tele, the screen randomly goes black and shows the resolution details at the top of the screen. Any ideas how to solve the problem?

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Robin's 1 post GB

9:31 PM

Robin: If you've attached it to your TV via a scart, make sure the scart is properly attached.

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MikeB's 2,579 posts GB
Monday, 13 January 2014
11:40 AM
Haywards Heath

RH16 3RX - Roof Aerial - Heathfield Transmitter.
Have been getting a lot of pixelation and blocking on all TV channels on multiplex D3+4.
Started before Xmas, improved, but now back again. Is this still atmospherics, or is it more sinister?

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SteveK's 6 posts GB
Tuesday, 28 January 2014
1:21 PM
Haywards Heath

Further to my post above, I have had an aerial installer examine the problem. He has decided that it is 4G interference and, because I am in a poor reception area and have signal booster, an inline 4G filter is no good and a masthead 4G filter was required.
Reception much improved as a result.

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SteveK's 6 posts GB

7:08 PM

SteveK: Yes, 4G or any other filter if it comes to it, always has to be installed preceding an amplifier because if not then said amplifier would be boosting the very frequency that the filter is designed to eliminate, or at least seriously reduce!

I find it interesting though that 4G was found to be affecting channels as far down as D3+4 on C49, as the swamping effect of a 4G transmitter has the maximum effect of C60 but tapering off on every channel downwards from C60, although its all connected with the ratio of the 4G's signal strength relative to that of the DTT signal, and of course you did say that you are located in a poor reception area.

Thanks for the report.

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jb38's 7,179 posts GB
Thursday, 13 February 2014
9:07 AM
Haywards Heath

jb38: As well as being in poor TV reception area, from aerial height I am in line of sight of a Vodafone 4G transmitter (there was great objection to the transmitter being erected when 3G was the next big thing) and which is only about 200 metres away as the crow flies. Aerial fitter says that the start of me having trouble coincided with the start of 4G from that transmitter.

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SteveK's 6 posts GB
Friday, 14 February 2014

9:15 PM

SteveK: When you say that you are line-of-sight with the Vodaphone mast are you purely referring the this in a visual sense and "not" connected with the direction that your aerial is facing? as the only Vodaphone mast that I can see on the Ofcoms mast locator is situated close to Northlands Avenue near to Janes Lane and which appears as being to the North of you, this then meaning that any signal received from that source is at nearly right angles (least sensitive area) to a mast pointing towards the Heathfield transmitter albeit that its just about in-line with reception from Crystal Palace.

I also checked out your location relative to that of the Heathfield transmitter using the terrain indicator, the result of being no glaringly obvious reasons for your bad reception being seen (by opening the undermentioned link) although if others in your area suffer from exactly the same C49 problem as yourself then some other factor has to be involved and which "might" possibly be connected with tuner input swamping being caused by a powerful 4G signal, although if this was the case then one would have expected the BBC on C52 to also be affected in one way or another.

The question being, do others in your area suffer from C49 reception problems?

Terrain between ( m a.g.l.) and (antenna m a.g.l.) - Optimising UK DTT Freeview and Radio aerial location

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jb38's 7,179 posts GB
Sunday, 16 March 2014
12:41 AM
Haywards Heath

You are correct in that my aerial points to Heathfield and so Vodafone's 4G signal is at right angles.
I am not aware of neighbours' problems generally (a lot are on Sky by the looks of it), apart from that a new neighbour collared my aerial engineer whilst he was here because he had poor reception too. He needed a 4G filter too, so my aerial engineer told me.
However, my immediate next door neighbour was having trouble with all BBC at the same time that I was having problems with C49 but has not had anything fitted and has not mentioned it since.
My situation is not absolutely perfect yet; I have had several bouts of freezing and blocking on C41 now, and everything on this was "not tuned" one evening this week.
I don't know if this is relevant, but my TV is a Sony with an early Freeview (2K?) tuner built in.

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SteveK's 6 posts GB
Saturday, 5 July 2014
11:11 AM

Hi, all my ARQB channels disappeared after adding new channels to my Panasonic recorder box a while ago (those channels disappeared on the Sony Brava TV around the same time too). Have tried the resetting procedure without aerial etc on both box and TV several times - the first time it seemed to have worked, with ITV4 showing perfect reception for a few minutes before breaking up completely. Now though, it still isn't working - either shows the channel but can't play or doesn't even pick it up at all.
This is the main TV system, but the two other systems in the house using the same aerial have unaffected signals. There are also no other devices plugged in to cause interference.
Very grateful for some insights as this is most frustrating...

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RC's 3 posts GB
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