We have a bi directional arerial with booster think its call "omni" it struggles with signals had mixed advice. that its very hard to get freeview due to low aerial. I need to upgrade the arerial, but how can I tell if it will be any better before I buy? The weather affects the signal as well as location been told to rescan at each location. our home tv picks up excellent freeview but the van on the drive does not. all tips and advice welcome.