new aerial not receiving digital?

Multi point aerial system already installed when we moved in. Have change existing aerial for a UNIX 52 flashy aerial thinking i'd get an even better picture through the top boxes [3 in all] No! we get bad pixilating [breaking up] or showing NO Signal on most digi channels. The cable from the new to the old is connected by an external box [new] for VHF-UHF 0-860 MHz. I'd post picy if I new how. The surplus of the cables are looped and taped to the aerial pole. I know all about the old saying 'If it aint broke then don't fix it' but thought I'd get a better picture. We're in West Sussex on the coast and main transmitter station is I.O.W and aerial set in same position as the old one. Someone did tell me I need a 'Brighton aerial [Don't ask] giving the stronger signal but it won't be picked up on an ordinary aerial. Any suggestions other than 'You should have left it alone' or 'I told you it won't work'.
Got nagged by e'r in doors to fit the new one as sometimes the digi's did pixilate on the old aerial. Now she's peeved the new one is worse. She now want's to waste more dosh going out and getting another aerial. At that point I put my foot down on e'r ead and said NO! the old one goes back on if I have to.