Is it me or are my Freeview channels jumping about?

MTJR · 20-11-2010, 19:37

Every so often, when watching the standard Freeview channels I have problems watching ITV1, CH4, CH5, ITV2, etc. My TV tells me that the channels don't exist. However, if I do a rescan of all digital channels then they usually reappear.

It happens on my BT Vision box too. Irrespective of whether I split the signal or just have one cable to one device from my aerial socket. So, I'm fairly convinced it's not the TV or Vision box.

Is it normal for them to move these channels around or are they pretty static? I couldn't put a time period on how often it happens but it's now happened enough to be becoming a pain.

AndyCambs · 20-11-2010, 19:41

Friend of mine generally lost some of his channels at a particular time of the year. Eventually it was put down to the tree outside blocking the signal when it was in full bloom.

MTJR · 20-11-2010, 19:46

I had considered stuff like that but it seems to be a group of channels on a particular multiplex or whatever it is they call it. It's not a massive problem because I obviously have a solution. It's just a pain in the bottom area.

nodrogd · 20-11-2010, 23:37

Sounds like you are losing Mux 2. If you are in a pre-switchover area and your reception is marginal then Mux 2 and Mux A (which carries ITV3 and Quest amongst others) are the most likely to cause problems, as they use less robust 64 QAM encoding.

Without having any idea where you are located or the aerial system in use I can't really give any more guidance.

MTJR · 21-11-2010, 16:24

Running off the Sudbury transmitter. I noticed that the MUX2 is running on low power but I still don't understand why a "re-tune" fixes the problem. Surely, if it's in one place then if it's there it should pick it up?

nodrogd · 21-11-2010, 17:45

There is a complication with Sudbury, particularly with the Pre-switchover channel allocation. Mux 2 is output on two UHF channels 56 and 68. The lower of the two channels can at a squeeze be picked up by the Group B analogue aerials that many may be using, but is at low power. The higher channel is 8 times more powerful, but is right at the end of the band and out of range of a Group B aerial.

To solve the problem a Group E or a Wideband aerial is required to receive all the Mux correctly.

When Sudbury switches over next year, the old analogue channels will be re-used so reception on Mux 2 will seem to put itself right. However the commercial Mux will still be "out of band", and these will cause problems instead. So if you are using your old analogue aerial, the best time to replace it is now, before all the cowboy installers start moving in.

Had the same problem as you with the Hemel Hempstead transmitter, where the Mux C & D channels are well "out of band" with the analogue aerials. Freeview sets would lock onto the Mux and add them to the channel list, but they were too weak to decode properly and would either pixelise or give a "No Service" message. Treated myself to a shiny new Wideband aerial. Problem solved!