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.
Just a wild guess, perhaps when the antenna was inside you were running in mono due to low signal level. Move outside and the tuner grabs for stereo which requires even more strength.

Also possible that signal is blocked where you live and there was a tiny "window" of reception right where the antenna was in the first place.

It's important too that the antenna is aimed at the transmitter, assuming your using something other than a whip (like on an automobile).
Fading can also be caused by multipath.
i=It was in sterio, i checked multipath and the meter read 0 on the tuner. It is a whip and direction did change in the house I had it laying accross a window so it was horozintal and outside it is on the roof virtical off about 40' of rg6 coax.
MD may make great tuners, but their antennas suck. Google directional outdoor antennas. After installation, you`ll enjoy the tuner & thank me.