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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

Monday, 3 September 2012
Mark Fletcher

6:35 PM

Kathleen.Without a full postcode preferably or a nearby location as such,we cannot be of any useful help to you.

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Mark Fletcher's 673 posts GB flag
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Mark Fletcher

6:36 PM

Richard Randall.SO15 area.I would look up inversion effect as a likely culprit.

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Mark Fletcher's 673 posts GB flag
Mark's: mapM's Freeview map terrainM's terrain plot wavesM's frequency data M's Freeview Detailed Coverage

7:51 PM

Kathleen: There are a number of reasons that cause your type of problem but the two main ones are broken coax if the cable comes straight from the aerial to the tv have a look at the aerial plug for rust or water the other cause can be an amplifier picking up the interferance this can be harder to solve this needs a full check on your system hope this helps

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Mazbar's 384 posts GB flag
Thursday, 6 September 2012
John Cameron
10:11 AM
Isle Of Islay

On the last occasion, Sept 4th. that I "lost" the BBC A group + radio it turned out that engineering had been in progress.
At other times, however, I lose this group (only) during, I have noted, persistant rainfall. (water on slate roof).This may indicate the BBC group signal is weaker - could this be the case? Thanks for your attention.

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John Cameron's 13 posts GB flag
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Sunday, 9 September 2012
B. O'Neill
10:27 AM

We receive our signal from the Divis transmitter in Belfast. Until a month ago we could receive all the Freeview channels perfectly. Then all the programmes on channel 33 disappeared, reappeared and finally disappeared. We have a new digital aerial, have cleared the channel list completely and then rescanned but still no channel 33 programmes. The aerial is going straight into the back of the TV. As all the other channels are great why is channel 33 having problems?

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B. O'Neill's 1 post GB flag
Dave Lindsay

2:06 PM

B. O'Neill: There has been engineering work taking place in preparation for switchover. We do not know what this was/is, but it is a possibility that it was something that may affect reception, particularly in areas where the current low-power signals are marginal (i.e. "only just" good enough).

It is possible that whilst the other channels are perhaps "only just" above the threshold required to produce a picture, that C33 is now "only just" below the threshold.

There is no such thing as a "digital aerial". Aerials work based on the frequencies of the signals that they are installed to receive.

In the days of four-channel analogue it was commonplace for aerials to be fitted that are most sensitive to the group of channels/frequencies used by the desired transmitter.

For Divis this is "Group A" which is the first or lowest third of frequencies used for TV. Before switchover all digital channels are within Group A except Mux C which is up on C48. In some cases (at some locations), the lower power pre-switchover digital signals may not be strong enough to be received (or "heard") by aerials that are sufficient for analogue. Where this is the case, replacement with a more sensitive aerial may yield reception of those digital channels. However, it is expected for Divis that, generally speaking, (Group A) aerials installed for analogue will work for digital after switchover on 24th October. This is because all of Divis' channels will be in Group A. The stronger signals should also mean that aerials that are more sensitive (higher gain) that were installed pre-switchover aren't necessary.

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Dave Lindsay's 5,724 posts GB flag
Wednesday, 12 September 2012
9:16 PM

Hi - my postcode is B61 0JG. I should be able to receive transmissions from the transmitter in Bromsgrove at Worms Ash. However the aerial installer before switchover said I was getting a signal from Malvern but at least that worked fine. I have two cheap digital boxes and they both have the same problem. If I retune one (Goodman's) you just get what it gives you but the other (Grundig) is a choice of Gloucester Central, Gloucestershire West, West and West Midlands. All four settings tell me the transmitter is in Gloucester. I struggle with UHF 47. Tonight I can pick up nothing from that others times I generally get a poor picture. Most other frequencies esp. BBC, ITV and C4 are fine so I think the TV, box, and aerial are OK. The problem looks to be the signal I am picking up. Advice apprecaited. More info supplied if required.

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philb's 1 post GB flag
philb's: mapP's Freeview map terrainP's terrain plot wavesP's frequency data P's Freeview Detailed Coverage
Saturday, 15 September 2012
Malcolm Watson
10:37 AM

Malcolm Watson
I have spent a considerable amount of money on new digital TV's and arial system(signals received from Sutton Coldfield transmitter).The TV's have built-in Freeview receivers.I have read all the possible causes of loss of signal reception, but the fact remains that I am not getting the sevice I expect or am paying for. Over the last month or so the situation has become much worse. My neighbours are also having regular problems with reception. What, if anything, is being done to correct the problem.

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Malcolm Watson's 1 post GB flag
Malcolm's: mapM's Freeview map terrainM's terrain plot wavesM's frequency data M's Freeview Detailed Coverage
Sunday, 23 September 2012
8:28 PM

Borehamwood, Herts. (23/09/12). Since the suggested retune last week the TV no longer receives any HD channels and all those on C25 have interference. Have retuned (manual and auto) a couple of times since but still no joy. Had enjoyed HD prior to this on the TV. The separate digi box recorder is not affected and all is fine and yet it runs off same aerial point (the TV is primary connection with dig box connected via a splitter). Any ideas? Think Crystal Palace is the transmitter. (51.6436,-0.2604) 

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Vik's 1 post GB flag
Friday, 28 September 2012
Sarah Bramley
12:41 PM

We are in the Tyne Tees area and phase 2 of the switchover happened on the 26th Sept. We have now lost Really, Dave, 5*, 5 US, Pick TV and Quest. We have unplugged the aerial and re-tuned, then re-tuned numerous other times, done a factory reset on the recorder box, etc, but to no avail. Any suggestions?

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Sarah Bramley's 2 posts GB flag
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