I don't consider myself an idiot when it comes to AV tech, but I'm frustrated beyond all h$ll

. I want to cut the cord on my sat. subscription, but I can't seem to get any antennas to work in my attic or even rooftop. Here's my signal survey:
http://www.tvfool.com/?option=com_wr...03f30f39257249
Here's what I've done so far, to no avail. What am I doing wrong?
1) Purchased 3 different antennas (from Meijer and Radio Shack). Ranges on the box very from 40-70 mile range. The stations from Detroit are less than 50 miles from my house. Also purchased 2 different signal amplifiers.
2) Climbed into my attic (boy it's hot in there!). Connected the coax from the bedroom directly to the antenna. Did a channel scan, but only detected 3 analog stations. Added a signal amplifier, but no more channels detected.
3) Bought two more antennas and tried them all. Can only detect the same 3 analog stations! Even climbed up on my roof, connected to the coax from by sat dish, and still had no digital channels detected. I have many tall trees between me and Detroit (Northeast), but they are about as tall as my house. So I figured if I stood on my roof the antenna(s) would work. But nope, nothing.
My TV is digital, but is about 8-10 years old.
Why do I get absolutely no signals?