[lyner]

The problem is that the new digital transponders are sharing the UHF bands with the analogue service. The original UHF TV plan was for 4 programmes. It does a fair job of providing a service to nearly everyone with enough signal and minimal co-channel and adjacent- channel interference.
A fifth channel was added in areas where it could co-exist safely. Now they have shoehorned a whole extra network of digital channels into the same spectrum space. That's a bit of a miracle and gets away with it because the digital signals appear to the analogue receivers as  noise ( snow) which is fairly acceptable at low levels. But there is a limit and the existing service takes second place until switchover, I'm afraid.
After that, we'll all get plenty of signal.

[Geezer]

Take it out of the freezer!

Cheeky bisom!

[Don_1 (OP)]

The problem is that the new digital transponders are sharing the UHF bands with the analogue service. The original UHF TV plan was for 4 programmes. It does a fair job of providing a service to nearly everyone with enough signal and minimal co-channel and adjacent- channel interference.
A fifth channel was added in areas where it could co-exist safely. Now they have shoehorned a whole extra network of digital channels into the same spectrum space. That's a bit of a miracle and gets away with it because the digital signals appear to the analogue receivers as  noise ( snow) which is fairly acceptable at low levels. But there is a limit and the existing service takes second place until switchover, I'm afraid.
After that, we'll all get plenty of signal.

Ah! That explains it. Thank you.

[techmind]

In much of the UK the digital signals are currently transmitted at lower power than in the analog equivalents, and the independent multiplexes (especially Mux D) has weaker error-correction and may be at even lower power too. So basically all else being equal, at present, digital can still struggle when analog is ok.

That said, aerials (especially if exposed to the elements outdoors) can degrade over time, and water can get into the cable, and the cables get eaten by rodents... so having a new aerial and cable may be no bad thing. Note that a lot of the wall-mounted aerial sockets are incredibly shoddy and will loose a lot of signal as are many common flyleads which go from the wall-socket to the receiver - they can also develop loose connections over time, which may not be immediately apparent on analog but can be enough to push DTT over the 'digital cliff'.

[lyner]

Are you offering to fix my installation?
(That's not a euphamism. Btw.)