No digital signal

SoozyJ22

The box is a Sagem PVR 7280T. It's not on the list of incompatible boxes and a quick google hasn't found anyone else with problems.

Moneymaker - it's not bouncing, it gives me various channels that I can scroll through to test the signal strength and some are 3%, others nearer 50 and the highest is 80%. It's consistent for each channel though.

Buzby

There's a good chance your communial distribution amplifiers have not been taken care of - is everyone else in the same boat?

SoozyJ22

Quick update. I spoke to my neighbour who runs our residents' committee this morning and he's had no problems with his Freeview and no-one else has mentioned any problems to him, so that pretty much rules out the aerial. I'm currently trying to find someone who can lend me a freeview box briefly so I can see if the problem's in the box itself or somewhere else.

Phones4Chris

Your neighbour has done a freeview retune and has no problems? Ask him what his BBC2 reception is like that can now only be got on Freeview (or Satellite). The other main channels are still available on analogue until DSO2.
Borrowing a box is a good idea also. Which ever transmitter the aerial is pointing at, you should get a reliable signal from either after full DSO.

If it turns out your neighbour has a problem with BBC2, the communal system could be channelised and need adjusting but as you've described the problem you may well be suffering signal overload. Transmitter power goes up a large amount at DSO.
The signal will not necessarily be bouncing around, but will look as though it is less than it was previously.. Looking at your aerial, are the side elements more of a squashed x-shape and running from side to side rather than up/down in which case it's horizontal.
In any event, I'd go over to uk,free.tv Crystal Palace page and put you postcode in the box in the top RHS and post about your problem there. There are plenty of technical experts to help.

SoozyJ22

Slightly delayed update.

I went out and bought a cheap freeview box and it works fine, so it looks like the old box was the problem. I now need to buy a new PVR, but that's not urgent until the Olympics so I have some time to work out the best one to buy.

Thanks again for all the help.