I have to have a 68db amp on mine to get channels, but most are faultless. Two things that affect recption are tropospheric propagation (google it) and mopeds. One of them fuckers come pas and the signal breaks and cracks like hell. Tropospheric propagation is to do with bouncing radio waves (RF signals) across the curvature or the globe and to do with different atmospheric levels. Weather is the biggest killer here - high and low pressure can change the signal strength easil. You might find when the weather clears up and settles out that you get much better reception. On bad pressure days I can lose all the Five channels, and often the ITV channels too. This is to do with mux's. A mux is a group of channels on one band - each mux is a band that can hold 5 or 6 channels. Some mux's are stronger than others, to do with bandwidth vs bit rate. So often the BBC mux's are stronger than the ITV mux's and five mux's, etc.

Best bet for the aerial is to put it outside for sure - Freeview is notoriously bad with indoor aerials!