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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

Tuesday, 2 September 2014

12:07 AM

Barrie Perkins: If the test that you carried out in the attic with a TV being coupled directly into the aerial downlead did not produce any results, that is when using the manual tune check procedure?, then the situation can only be looked at along the lines of (1) : the actual aerial is defective, something which I somewhat doubt if its reasonably new?, or (2) : that the data content of the signal being received is corrupted to the extent that it cannot be decoded, hence zero quality.

I do have to say though, that many areas in Northamptonshire are prone to suffering from erratic reception problems at various times of the year, basically due the areas in question being screened from the transmitter by the layout of the terrain, and indeed a terrain indicator check revealing (link for below) your location to be particularly bad in this respect, with the signal path from the transmitter being severely blocked from just under 11 miles right down to approximately 1 mile prior to your particular spot.

Another potential problem I noticed being that aerials in your area would appear to be facing into a bank of trees, something with can cause no end of problems with DTT reception dependant on whether the foliage is wet or dry, plus being coupled to the density of same.

I do have to say, that in my opinion you are really fighting a losing battle, as locations suffering from signal blockages of a magnitude such as seen on the indicator are, and always will, be prone to totally erratic reception due to any signal that is received being purely by diffraction (signal bending), atmospheric as well as weather conditions nearly always playing a role in whether a signal is received or not.

Apart from the actual aerial, have you verified that the booster is still operative? best way to check being to take note of the signal level and observe if this drops back when the power supply to the booster is switched off, which of course it should.

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 flag
Tuesday, 9 September 2014
Glen Harnden
10:07 PM

Hello, I live on the Malvern Hills, Worcestershire, Until about a year ago I could receive all the channels from the Wenvo transmitter, which I admit is outside the normal reception range, but due to our elevation, signals are good. However for the past year or more I cannot get many of the channels. After studying the program/channel list for the Wenvo transmitter I realise that I am not receiving the signals from channels 41, 44 and 47, the most powerful transmitters. Now I have a modern all singing and dancing Panasonic tv, I put this into its signal diagnostic mode and I find that the indicated signal strength for the mentioned channels is very good at strength 9 or 10 ( in a range of 0-10), but the indicated "Signal Quality" is zero. I am an electronics engineer, but this is baffling me, could it be due to some sort of co-channel interference? Your input or advice would be much appreciated.
Regards Glen Harnden.

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Glen Harnden's 1 post GB flag
Dave Lindsay

11:01 PM

Glen Harnden: See pages on this site for C41, C44 and C47. Could it be The Wrekin, which is horizontally polarised, and a SFN with Lark Stone (which is vertically polarised)?

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Dave Lindsay's 5,724 posts GB flag
Tuesday, 23 September 2014
6:39 PM

Hi I'm having a similar problem. I recently moved into a new student house. Originally we had all the channels on our digital tv but lately we seem to either get only all the BBC channels or only everything else. It seems to change which one it finds each time I retune at different times. Have tried a system reboot to no avail. Any ideas?

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MattB's 1 post GB flag
Wednesday, 24 September 2014
2:11 PM

Since the recent updates, I have lost EPG, on 2/bbc2.4/ chann 4./5 chann 5/.6 itv2./7 bbc3./9 bbc4./13 4+1/14 more 4./15 film4 and 28 e4, is this likely a signal strength problem? I am at Peterborough pe3 and transmitter is Waltham....Toshiba Regza

have done the suggested retune aerial in/out etc.....suggestions please

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bob's 1 post GB flag
bob's: mapB's Freeview map terrainB's terrain plot wavesB's frequency data B's Freeview Detailed Coverage
Tuesday, 27 January 2015
8:38 AM

Hi, I have a hd freeview tv downstairs that shares the same aerial as my freeview tv upstairs. I am now finding the tv upstairs suffers interference when the tv downstairs is on standby, if I turn the tv downstairs on its ok and if I turn it off by the main plug switch it is ok, it's only when on standby. Any ideas on the reason for this?

Many thanks

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Darren's 1 post GB flag
Saturday, 31 January 2015
2:33 PM

I live in Hythe Hampshire my signal is from the Isle of wight. Everything other than channel 25 mux is fine but all stations on channel 25 are not watchable. I use a BT vision box I don't have sky but the problem is there all the time even if I connect the TVs direct to the antenna. Does anyone have any ideas? My antenna is a loft mounted wide reception job.

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Graham's 1 post GB flag

4:15 PM

Graham: A postcode might would an explaination of 'not watchable'.

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MikeB's 2,579 posts GB flag
Thursday, 27 August 2015
B Moyse
5:52 PM

I loose the signal from mendip at 18.10 each evening for around 15 to 20 mins , is a problem with the transmitter, my areal it set.

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B Moyse's 1 post GB flag
Saturday, 24 October 2015
9:17 AM

I live at NE23 3QS and have had perfect signal reception on all channels until about 1 month.

BBC channels are fine, on ITV channels however I now get break up of the signal. I have looked at the signal strength for the BBC channels and it is constant at 44% with 100% signal quality.
ITV channels signal strength fluctuates between 44% and 49%, changing second by second, and then suddenly drop to 0%.

The problem is more noticeable in the evening, with not much interference during the day.

It would appear from reading your information that I have single frequency interference.
Why is this occurring now?
We have not installed any new equipment (fridges etc.) and I don't want to pay for the fitting of a new antenna if this is not my fault.
I have tried retuning my Youview box and I have also retuned the box which is incorporated in my TV. Both to no avail.

Hoping for a quick cheap answer

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Bill's 1 post GB flag
Bill's: mapB's Freeview map terrainB's terrain plot wavesB's frequency data B's Freeview Detailed Coverage
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