Tuner fading out how to fix.

I MD 102 that I put in and there antenna I mounted on the roof. The antenna when I had it in doors worked fine but once I mounted it the stations appear to have more static. Also I get a fading in and out that actually changes volume. What can I do to help this it really makes this unenjoyable to use. Will a signal sleuth help? Why is it worse, I do pick up more stations now.