You need to change your aerial to a wide-band .The thing is that aerials come in three groups,a, b, and c/d. You have one of those.Where your transmitter once transmitted on just one of those bands ,the digital signal uses all three
hence the need of a wide-band aerial. If you live close to the transmitter there is no need to spend a lot on an aerial.
I got mine from Focus for �8.99. The cowboys of course
will tell you that you need one of their elaborate ones for
around �150.00