Single frequency interference
Brian Butterworth published on UK Free TV There are several different type of interference that cause problems. This page deals with the situation where:
- Freeview reception is perfect or near-perfect most of the time
- Several channels are missing, but they are all on the same 'multiplex'
Local analogue interference
Local analogue interference is caused by household video devices that you can attach to a television such as: 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?
Monday, 21 November 2011
Tuesday, 22 November 2011
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Simon5:04 PM
Tarporley
Thanks very much for all the suggestions. I've got new satellite cable with enough length to point to the Midlands ! hey presto Thanks again.
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Simon's: mapS's Freeview map terrainS's terrain plot wavesS's frequency data S's Freeview Detailed Coverage
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Mark Fletcher5:27 PM
Halifax
It was a pleasure we have been of assistance to you,happy viewing !
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Mark's: mapM's Freeview map terrainM's terrain plot wavesM's frequency data M's Freeview Detailed Coverage
Thursday, 24 November 2011
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Jen5:08 PM
Corby
Hi. I have lost multiplex 2 since changing my t.v. There is nothing else connected to the tv so it's not local analogue interference and as I had the channels on a previous tv literally 2 minutes before the new one was plugged in I know the aerial is fine, we are also receiving them upstairs. I have followed all retuning advice I could find and still can't get them back. Please someone help me. Typically they are the most watched channels in the house. Post code NN17 2QR. Thank you
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Jen's: mapJ's Freeview map terrainJ's terrain plot wavesJ's frequency data J's Freeview Detailed Coverage
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Mark Fletcher5:53 PM
Halifax
Jen.NN17 2QR.Do you reside in Corby,Northamptonshire.Is yer aerial polarised horizontally and if so is it directed either at Sandy Heath (BBC1 East,Cambridgeshire & ITV1 Anglia,West) or Waltham (BBC1 East Midlands & ITV1 Central,East) or possibly either at Sutton Coldfield (BBC1 West Midlands & ITV1 Central,West) or maybe Oxford (BBC1 South,Oxford & ITV1 Meridian,North).Try manually scanning the TV you stated that is affected by inputting the affected multiplex as such which ya mentioned is multiplex 2 now known as D3+4 mux,if you are on Sandy Heath D3+4 multiplex is on frequency 24 or on Waltham D3+4 mux is on fr 54,if you receive Sutton Coldfield then mux D3+4 is on frequency 46 or in the case of Oxford multiplex D3+4 is on frequency 60.Give it a try and see if it works.
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Mark's: mapM's Freeview map terrainM's terrain plot wavesM's frequency data M's Freeview Detailed Coverage
Tuesday, 29 November 2011
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RENJIL3:06 PM
Waterlooville
I'M ONLY GETTING : BBC4,BBC PARLIAMENT,303,SKY SPORTS1&2. WHY I'AM NOT GETTING OTHER CHANNELS?
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RENJIL's: mapR's Freeview map terrainR's terrain plot wavesR's frequency data R's Freeview Detailed Coverage
Thursday, 1 December 2011
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jb385:11 PM
Andrew: As you are only 16 miles away from Emley Moor its very possible that the signal you are receiving from the BBC multiplex on your outdoor aerial is slightly too powerful and is blocking your receiving equipments tuner, the indoor aerial giving less signal to the tuner hence its not blocking it, likewise enabling you to tune in the BBC on Mux Ch47 (682.0 Mhz)
The only way around the problem is to purchase an attenuator to place in line with your TV or box, something between about 6dB or so should suffice, although variable types are better as they can be fine tuned.
It should be appreciated that although the transmitter power levels are all the same its not necessarily the case that they will be received at exactly the same strength, as they radiate from different levels on the mast.
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Andrew7:33 PM
Leeds
Thanks for the reply , the signal actually shows as 'poor' , would this be the case if it was too powerful ? and I also can't understand why it has suddenly done this , when it has been fine for that last 3/4 years ?
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Andrew's: mapA's Freeview map terrainA's terrain plot wavesA's frequency data A's Freeview Detailed Coverage
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jb388:56 PM
Andrew: Although only tests would prove the point either way, in cases where a signal is strong to the point of causing instability in a tuner (swamping) the system used for measuring the signal strength gets completely upset, whereby anything indicated doesn't really bear any resemblance to the true signal strength, with only a proper (professional) signal meter being able to reveal this.
The aspect of this type of situation that can mislead the unwary is, that the indications seen via a TV's signal check menu whilst equipment is operating under these conditions is "exactly" the same as observed when a genuinely weak signal is in evidence, so yes! it is possible for the strength to indicate low.
Remote faulting is notoriously difficult at the best of times as a person has to use their knowledge to assess the possible cause of a problem purely from what's being reported, but the symptoms you report of the BBC working OK on your indoor aerial but not when on the outdoor one, coupled to the knowledge of the distance you are from the high powered (175kW) transmitter, strongly suggests that you are experiencing the classic symptoms of and over powerful signal.
This being said though based on you singling out the BBC as not working on the outdoor aerial, as if had been everything then that could then have indicated a faulty connection on the aerial, or that the signal was really over the top in power, something which can completely block reception of everything.
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Andrew10:14 PM
Leeds
Ok - thanks again , I will try and see if neighbours are having any problems , and then probably look to getting someone to check it out properly , all other channels OK , and BBC was fine until beginning of week.
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Andrew's: mapA's Freeview map terrainA's terrain plot wavesA's frequency data A's Freeview Detailed Coverage
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