I don't experience the problem because I don't have roof mounted antenna. I only view Foxtel and hence don't need an antenna. I did get an indoor antenna from Dick Smith's(their brand) as a token gesture incase someone wanted to view commercial free to air tv. It performed very poorly when I had the analogue tv(going through a set top box). And yes, it has a powered booster. BUT, once I got the digital Plasma with built in high def digital tuners(hence, no set box required for the free to air) the commercial free to air channels all work crystal clear.
The next time it rains hard if I lose Foxtel I'll make an effort to switch over to free to air and see if I've lost them also. Sorry I'm not much help with your problem.
Also, some areas experience 'off the cliff.' In my last location I lived opposite a low mountain range. On the range is where the stations have their antennas. Apparently the signal 'rolling' down the cliff can break up. Also, I experienced the odd problem with air planes distrusting the signal, though they were high up. Another interesting problem I read was with a neighbour's fluorescent lighting affecting the signal. I believe these issues were more prevalent when using a set top box. Built in high def tuners are much more stronger as them and the tv are 'all one.'
I gather your tv's are high definition digital. I'm not sure if standard definition digital experiences more problems.
