You're in a 200-300' deep topographical hole less than a 1/4 mile from the valley walls. At best, reception is going to be hit or miss due to the severe shadowing from the northeast in particular. Most likely, the signals simply aren't there unless you happen to get a reflection from the opposite side of the valley.
Go ahead and try a pre-amp, there's no risk of signal overload.
Estimated location:
