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Two frequency interference

What to do when Freeview reception is perfect, but several channels are missing, and they are all on the just two 'multiplexes'.

What to do when Freeview reception is perfect, but several chan
published on UK Free TV

There are several different type of interference that causes problems. This page deals with the situation where:

  • Freeview reception is perfect or near-perfect most of the time
  • Several channels are missing, and they are all on the just two 'multiplexes'
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 two rows, you have "two frequency interference":



Transmission mode problem

If you are unable to receive the channels on BOTH multiplex 2 and multiplex A, this will be down to the transmission mode. See Freeview modes.

This is a particular problem for people using Loft aerials and Indoor aerials .

Non-wideband aerial in some areas

In some places you will need a wideband aerial to receive all the Freeview multiplexes. To find out if you need an aerial upgrade, see My Freeview reception.

Help with Freeview, aerials?
My Freeview box has no EPG, is blank on FIVE, ITV3, ITV4, ITV2+1, has no sound o1
My ITV/C4 Freeview channels have disappeared - what can I do? Is it my SCART ca2
I have now lost all signal can you tell me what the problem might be?3
Is it possible to receive freeview cahnnels via a broadband internet connectio4
My high gain aerial can't get all the Freeview channels I expected5
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
Single frequency interference6

Comments
Sunday, 11 September 2011
M
Mike Dimmick
12:45 PM

jen: Multiplex C and D - after switchover we usually call them ArqA and ArqB - are still on relatively low power from Belmont. If you didn't have digital before switchover you might still have a Group A aerial, and these multiplexes are on much higher frequencies that the aerial doesn't pick up. You really need a wideband for all services.

I'm surprised anything is missing from Multiplex A/SDN, usually you get all of a multiplex or none of it. Do the channels appear anywhere else in the list, maybe around 800? If so, your box might have trouble with the size of the Network Information Table. A list of some boxes known to have trouble is at http://www.digitaluk.co.u…tnit .

link to this
Mike Dimmick's 2,486 posts Platinum Platinum GB
Wednesday, 30 November 2011
J
John W
8:00 PM Harrow

Hi,

Any idea why I have lost all Mux 2 completely and have seriously reduced signals on Mux 1?

My transmitter is Crystal Palace and this has worked fine last week when these channels on these 2 Muxs just vanished. It's occurred on all the Freeview boxes and the Freeview TV.

We do have a loft arial, but as I say its worked for years with no problems till last week. I'm around 30K from the transmitter. HA1 postcode.

link to this
John W's 2 posts GB
John's: Freeview map terrain plot frequency data R&TI Service digitaluk trade DAB coverage
Wednesday, 7 December 2011
Wednesday, 29 May 2013
J
John bevan
4:43 PM

I have two problems when recording BBC1 on my hard disc recorder.
I have 2 channels 001 and 800 1 is london 800 is bbceast .When I ask my program guide to series record it sometimes will not give me the option on 1 only on 800. If I use 800 some times it does not work because of a weak signel.
Last week I retuned the recorder and managed to use 1 for my programs. This week suddenly the recorder switched itself to 800 and blocked the timer when it was unable to record the program . This morning I switched it on and checked the timer settings and they were all back to 1 . I then tried to reset a program that I had canceled due to the problem but when I tried to put series record on 1 it refused to give me the option. Any Ideas what I can do. I have had a problem in the past of my recorder picking up bbc se and switching my selections in a similar way .I solved this problem by retuning and the se channel is not so close and has not come back.

link to this
John bevan's 1 post GB
M
MikeB
10:17 PM Peterborough

John bevan: My Sony PVR does something very similar, and in the past we've accidently recorded on 803/811 (which as you say, doesn't work), rather than channel 1.

Although this is normally accidental, Case Histories hung up for the same reason last week, and since I'm fairly sure that I did set it for one, its possible that it did the same thing as yours.

However, Waltham changed channels this morning, and I noticed that after the full retune, the EPG only showed ITV & ITV +1 on the 800's, with the multiple BBC 1 800's totally gone.

I'm sure someone more expert than me can come up with an better explaination, but I'm wondering what your reception is like at your location generally.

800's are generated by having signals from one than one transmitter, so have a check which BBC1 channel has the strongest signal, and where its from. It could be that your aerial is pointing at the wrong transmitter, or there is something that stops you getting the best signal from the right one.

You can also kill off a weaker signal by reducing the power of the signal you get.

There are a fair number of websites which mention this problem, and perhaps they might be able to help. BTW - if you mention your postcode, transmitter and model of the PVR, one of the gurus here might be able to help.


link to this
MikeB's 1,886 posts Gold Gold GB
MikeB's: Freeview map terrain plot frequency data R&TI Service digitaluk trade DAB coverage
Thursday, 8 August 2013
D
daz
9:23 PM

hi i have a toshiba smart tv run sky dvd recorder and blu ray into yamaha receiver had ordinary hdmi3d leads because of space at back of tv replaced hdmi with right angled 3d hdmi on one of them when i turn the flurecent light on in the kitchen it makes the picture go of for about a second on the others it is alright with the other hdmi i had it did not do this any thoughts thanks

link to this
daz's 1 post GB
M
MikeB
11:22 PM

daz: Sounds like a dodgy HDMI or poor fitting - with the light's starter causing interference - try swapping it for a new one (they are not expensive - the right angled ones are about a fiver from Maplin, etc) 

link to this
MikeB's 1,886 posts Gold Gold GB
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