Scott,
On that antenna finder list it gives the two different frequencies of the TV channels. One is the major RF channel and the other is the digital channel(Virtual). I believe with your converter box, you will only be able to tune in the analog channels such as UHF channel 40 and not the digital channel 39.1. Some of the newer TV's allow you to tune to the digital channels but I am not sure if the converter box does offer that capability.
Yes the terrain does affect your reception. In most cases, the higher you are the better. Even a lot of clouds can cut down on your reception.