Reception help 98011

[starboard5]

Hello, all. I'm new to antennas and certainly no technical wizard, just a dad trying to save a dime and get a few channels.

First, my problem, then my stats.

So we live just northeast of Seattle, our house is exactly 11.0 miles as the crow flies to the transmission towers in Seattle. These couple of towers are just 50ft or so apart and carry the major networks out of Seattle. My research tells me at our distance from the towers, there are only 2-3 degrees of difference in signal direction between these couple of towers. So the problem is I get a beautiful 1080i image from ABC, and beautiful but very intermittent (actually mostly no signal at all) from NBC, and never CBS. If i get on the roof and monkey a little I can get CBS and some NBC, but lose ABC. I just about always have a crystal clear image from a FOX station that's over 20 miles further away, but can't get the Seattle one at all, not that I care, just illustrating my frustration. I've tried an amplifier right inside the house with no luck. I get PBS and CW perfectly fine even though they come from towers many degrees off from the main network towers I'm pointing at. Its very frustrating and makes no sense to me.

Stats:

Location: 98011
Antenna: Antennacraft HBU55 from Radio Shack
Antenna height: extends about 15-20 ft from the top of our two story house (guessing 40+ ft from the ground?)
Geography: We live near the top of a high hill, but are slightly on the downhill side opposite Seattle and there are a number of homes between us and the hill's crest, but none larger than ours. The area is not heavily wooded but there are a decent amount of very tall pine, cedar, and oaks.

So do I need a stronger antenna? A taller house? My own satellite?

Any help/suggestions are greatly appreciated.

Thanks so much
Dan