A couple of years after it was going, Roger W0WUG (sk) got some propagation modeling software to test and review for one of the industry magazines.
We plugged in the data for the path from my QTH to the Cold Spring site @ 1400'+ and there were two knife edge diffraction zones that probably made it work.
Each bent some of the signal downwards from a high spot along the path curving it from going off into space.
Because of the tall location Dan Karg K0TI had at the metro end, there was a clear path to Mpls from Cold Spring.
Circa 1994-95
73
Mike N0QBH
N0QBH Mike Berg