I am in a weak digital signal area but what I did to obtain a very good signal from our block of flats communal ariel (that incidentently should be, most importantly
'high gain' in a 'weak' signal area is:
1. Rewire with new digital standard cable from the ariel / junction box
2. Install a SLx Masthead booster at the point of cable entry into the property (if you cannot get onto the roof and rig the ariel, that, to repeat must be 'high gain' in a weak signal area, as I have previously done when living in a house).
3. Install a powered 2/3/4 Maxview booster and distributor box, after the Masthead box, in main cable feed.
4. Lay separate digital cable trails to each tv point required.
5. Plug in any good (Philips, Hitachi, etc,..NOT the cheap crap ones!) digital receiver box per tv.
This will give you a greatly enhanced signal that in most areas (unless the digital signal is pityfully weak!) should give you digital reception of a good standard.

All the parts mentioned are available from B & Q, and the above system also worked in my previous houses if we didn't have Sky.