Thanks for the active link. When you click on a station call sign, you get a graphical display of the path profile... The transmitter is shown on the left, terrain cross section in the middle and your receiving location on the far right. Looking at
WEMT as an example, you see the tall mountain ridge that blocks your line of sight toward the transmitter.
The HD7084P and preamp is still the best suggestion I've got. Higher is better no doubt.