I used to live in a tower block in Limehouse with line of site to the Crystal Palace transmitter. The block had a communal aerial which broke one day and I discovered the signal with an indoor aerial was crap. By chance I met the man who came to repair the communal aerial in the lift and asked him how much amplification there was on the signal. He pointed out, very politely I thought, that with the strength of signal amplification wasn't a problem - he gave me 3, 6 and 9db attenuators to try out with the indoor aerial. With the 9db attenuator on the aerial I found the signal gave perfect results. Apparently the reflected signals from other points interfered with the main signal, the attenuator could cut the effect of those down withiout reducing the main signal toomuch.
Also explained why I could cause interference on my FM radio by walking round the kitchen.
Digital signals shouldn't have such problems with the high signal power as it will be less likely to be impacted by interference.