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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?
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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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Digital Region Overlap4
Freeview reception has changed?5
Two frequency interference 6

Sunday, 15 April 2012
12:01 PM

I am in East-Sussex, Lewes. It is confusing because a Friend of mine living only 5 minutes away (walking distance) has no problems. It is Heathfield, I assume, and the switch is due to happen but why so many inconsistencies as it was no issue in 2007?

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Emma's 2 posts GB flag
Emma's: mapE's Freeview map terrainE's terrain plot wavesE's frequency data E's Freeview Detailed Coverage

2:06 PM

Emma: The Digital UK postcode checker shows that you are predicted to have good reception from Heathfield, both now and after switchover. However this does not take into account possible problems from any local obstructions in the signal path, such as trees or tall buildings which might not have been an issue in the past. Additionally, as switchover has progressed there are more high power digital transmitters in service, both in England and on the continent which can either cause interference to the current low power signals from Heathfield, or cause your receiver to tune to the wrong transmitter, resulting in an unreliable set of channels being stored. On 18th april 2012 the power of MuxB from Heathfield on C47 is set to be increased to 2kW to take account of anticipated interference from Hannington, which on that date, has a removal of the restriction on the signal sent out in your direction on C47. Regarding your friend having better teception than you do, it is quite possible for reception to be completely different when moving an aerial a matter of inches in any particular direction, resulting in next-door neighbours sometimes having completely different reception. As your switchover is only a few weeks away it is not really worth exploring whether changing the aerial position would improve reception at your location, but it is worthwhile checking the condition of cables and connectors, also making sure that correct Heathfield frequencies have been stored by the receiver on each mux.

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KMJ,Derby's 1,811 posts GB flag
6:32 PM

Just lost ITV4 and the rest of mux D on Humax PVR but TV ok (92% signal). postcode ox10 6rz.

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Ian's 3 posts GB flag
Ian's: mapI's Freeview map terrainI's terrain plot wavesI's frequency data I's Freeview Detailed Coverage
e johnson
7:37 PM

i have a proline tv that freezes quite often and the sound goes out of sync. All other tvs in the house are fine, I have a loft aerial and a 6 way distribution unit feeding 4 rooms. I have replaced all the cabling for this tv with good quality low loss satelite cable rather than the cheap coaxial. I have a surge protection extension cable for the tv. When I use a dedicaticated freeview box and connect through a vcr there isn't a problem. I have tried a different socket in the distribution unit. I have tried adding a secondary booster, i have retuned and added channels manually - no change. Anyone got any ideas, postcode gu32 3yr

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e johnson's 1 post EU flag
e's: mapE's Freeview map terrainE's terrain plot wavesE's frequency data E's Freeview Detailed Coverage
Wednesday, 18 April 2012
Tony Browne
1:39 PM

Re Rowridge 18 April.
I've re-tuned before OK. I've re-tuned today and my channels have gone from over 100 to just 46. The re-tune claims to be successful. All channels in groups (30->25), (37->22) & (32->28) are missing ("No Signal").

Are they actually being transmitted? Will it happen later (today)?

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Tony Browne's 1 post GB flag
Dave Lindsay

1:46 PM

Tony Browne: Where are you? To the west there is Stockland Hill which uses the same channels and in the east there is Crystal Palace which does. There are probably others that might interfere in places.

In some locations adjusting the aerial from horizontal may be helpful for reception of the three Commercial channels you refer to.

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Dave Lindsay's 5,724 posts GB flag
Peter Danckwerts
5:11 PM

I made several full resets this morning and was prompted to do another one this afternoon. The SD channels are fine but there are no HD ones. Sois this single frquency interference? I can't see how. I have no devices connected to my (full HD) television.

My television disgnostics indicate 100% signal strength and no errors.

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Peter Danckwerts's 3 posts GB flag
Thursday, 19 April 2012
Peter Danckwerts
5:34 PM

Peter Danckwerts: I saw that before I posted. My understanding is that our television has Freeview HD but I've seen contradictory information since I posted yesterday, which is very frustrating. It's a Samsung UE27D500NWXXU. Frankly, there has been a lot of (probably intentional) misinformation. My wife bought it and I've no idea what the salesman told her.

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Peter Danckwerts's 3 posts GB flag
Peter's: mapP's Freeview map terrainP's terrain plot wavesP's frequency data P's Freeview Detailed Coverage
Dave Lindsay

5:47 PM

Peter Danckwerts: See here for the specification:

27-inch D5000 Series 5 Full HD 1080p LED TV | UE27D5000NW - Samsung UK - TECH SPECS

Under "System" it says "DTV Reception DVB-T / C", so no, it doesn't have the ability to receive Freeview HD signals over the air as they use DVB-T2.

It is "Full HD" which means that it will show HD pictures in the resolution 1080p. Despite how this "may" be interpreted by some, it does not give any qualification to the Freeview part of TV being able to decode HD signals.

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Dave Lindsay's 5,724 posts GB flag
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