I looked back through the thread to see what tuner was being discussed
but could not locate it. It sounds as if it might the Cambridge Audio
Azur 640T. The manual indeed says nothing about the 'signal strength'
bar and my experience of the bar is that it sits at maximum even with a
very poor aerial and is not much use to help with aerial placement.

The only time it shows much less than maximum, is when the reciever
loses lock on the DAB signal and dies. BTW this is apparently
(according to the forum on CA website) a known problem soon to be
fixed.

Robert