TV BOOSTER signall. I have just changed my TV booster, as my previous booster was only 2way, and I have 4 TVs

running in my house. To avoid using SPLITTERS I got this new 4way booster. The signall is reasonably good, but I seem to have little waves or shimmers running up the picture on some of the channels. What might be causing this to happen. I did not have them on my old booster. I am using a ROOFYOP ariel and OGUE tv.with the UK progms, BBC1 BBC2 ITV CH4 etc. Would appreciate any ideas. Thanks