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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

Sunday, 2 October 2011
Andrew McPartland
10:20 PM

Hi I live in Stevenage , I recently bought a Technika stbhdh2010 box from Tesco for my daughters room.I have run off the existing aerial coming from the roof (an extremely long run as it goes down to the ground floor then back up to our room and across to her room). The box seems to be working quite well although she is missing ITV, C4, C5, etc. (looks like one multiplex). When I first installed the box, I mistakenly selected the option to use the London transmitter which is quite far away and not the Sandy Heath transmitter. Does anyone know how to change transmitters on this box, as it seems that it will let me re-tune, etc. but I can't find any option to change which transmitter I receive the signal from. Or will re-routing the aerial help, or installing a loft aerial? Any advice, please?

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Andrew McPartland's 2 posts GB flag
Andrew's: mapA's Freeview map terrainA's terrain plot wavesA's frequency data A's Freeview Detailed Coverage
Mike Dimmick

11:28 PM

Andrew McPartland: There's a manual for this box at TV Re-tune productmanuals (or at least STBHDIS2010 which I assume is very similar). Have you tried using the Factory Reset feature, to see if that will allow you to select a different transmitter?

You should always select whichever transmitter the aerial is pointing to, not the nearest to you, as the aerial is directional - it is designed to reject signals from other directions. (This is not perfect rejection, some signal from other directions is still picked up.) Crystal Palace is slightly east of due south, while Sandy Heath is slightly west of due north.

For best results when feeding multiple rooms, you should split the cable as close to the aerial as possible. Try to avoid using amplification if you can; if you can't, add just enough to offset the loss in the splitter.

Digital UK do predict that the chance of reliable reception from Crystal Palace is poorer on Multiplex 2 than on the other multiplexes, at present. A long cable run will make this more difficult. It's expected to be better after switchover.

If using Crystal Palace you will need to retune on 4 and 18 April 2012, for switchover; if using Sandy Heath there are retunes on 23 November 2011 and 9 May 2012. On both occasions it's recommended that you do a factory reset.

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Mike Dimmick's 2,486 posts GB flag
Monday, 3 October 2011
Andrew McPartland
3:30 PM

Thanks for the reply, Mike.
I can't find another manual for this box, although I have noticed that the aerial is facing south from me, ie. towards London, so perhaps I am best to leave it.
I have a few ideas about shortening the cable run, I will try those first.
If that does not help I will consider getting a new loft aerial, which will considerably shorten the cable runs and hope that switchover in April will improve the situation.

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Andrew McPartland's 2 posts GB flag
Andrew's: mapA's Freeview map terrainA's terrain plot wavesA's frequency data A's Freeview Detailed Coverage
Tuesday, 4 October 2011
elizabeth duke
10:21 AM
Leamington Spa

My address is Leamington spa, CV31 1JL I have an integrated digital TV (ie no set top box)
I recently re-scanned all my channels, several times and picked up the odd channel which I was previously unable to get (eg ITV3). Sadly and annoyingly, I cannot now receive Channel 4, although I can get the other channels in that same multiplex. So my problem is a single channel.

Any ideas as what to do next?

Thank you.

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elizabeth duke's 1 post GB flag
elizabeth's: mapE's Freeview map terrainE's terrain plot wavesE's frequency data E's Freeview Detailed Coverage
Wednesday, 5 October 2011
Monday, 10 October 2011
Sue Purkis
3:18 PM

We live in Tring on borderline between Oxford and Sandy Heath transmitter, and used to get good reception from Oxford (to which we were tuned) before complete digital switchover in September. Now all our channel numbers are up around the 800s, and the digibox keeps freezing and so stops recording. This site says we should be using the Sandy Heath transmitter for our postcode - does this mean we cannot use the Oxford transmitter any more (i.e. things are never going to improve) and therefore we have to get someone on the roof to move the aerial round? (Don't want the expense if it's going to make no difference.) Are the 800 numbers worse for reception? Or is it more likely a problem with the digibox? Or both? Anyone else had this problem since Oxford changed over? I thought the digi changeover was supposed to boost the power/reception.

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Sue Purkis's 2 posts GB flag
Sue's: mapS's Freeview map terrainS's terrain plot wavesS's frequency data S's Freeview Detailed Coverage
Adam B

5:00 PM

Sue Purkis:

Oxford is the best transmitter for you to use. What I think is happening to you also happened to me at switchover/retune, and that the high power Sandy Heath transmission is being picked up. The thing to do is to remove the aerial from your TV/set top box, do a full retune to clear out all channels, reinsert the aerial, and manually tune in each multiplex from Oxford. the frequencies for Oxford are UHF channels 53, 55, 57(HD), 59, 60 and 62. If your TV/box doesn't allow manual tuning, remove the aerial, do a full auto retune, but put the areial back in when tuning for channels above CH50 is about to start.

Hope this helps,

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Adam B's 91 posts GB flag
Adam's: mapA's Freeview map terrainA's terrain plot wavesA's frequency data A's Freeview Detailed Coverage
Sue Purkis
6:10 PM

Thank you Adam B. Will give this a go.

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Sue Purkis's 2 posts GB flag
Sue's: mapS's Freeview map terrainS's terrain plot wavesS's frequency data S's Freeview Detailed Coverage
6:16 PM

Hi we have just moved to the UK since July and the TV w bought is a second hand Sony ( model number kv28fx20u) and we have had no problem watching the terrestrial channels but seem to have lost all reception since the switch over. Could you please point me to the right direction as to how I can get the channels back.

Many thanks!

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Sam's 1 post GB flag

8:03 PM

Sam: It is likely that this receiver is a model that does not support the 8k mode, so will not work after switchover.(The 28DS20 which has the same chassis is on the list of such equipment). You will need to connect a Freeview box to this receiver to continue viewing digital terrestrial transmissions.

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KMJ,Derby's 1,811 posts GB flag
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