[ADTech]

Your signals from Lookout Mountain are sharply diffracted by Greene Mountain which is in your line of sight. The calculations from the signal analysis are, at best, estimates and there's really no point in wasting computational resources messing with small increments within the simulator since the simulator uses a 100 m square average terrain block size. Your line of sight to LOM is on the side slope of Greene Mountain and precision simply doesn't exist for your situation.

Your best course of action would be to try several different locations for the antenna (don't drill any holes yet) to see if you can find a better location that allows satisfactory reception of all the desired signals. The current location is either a "dead spot" for channel 31 or just happens to be in the path of a strong reflection from something nearby. Moving the antenna by as little as 6-12 inches in any direction might be enough to clear up the problem. The drawback is that what works for one channel's signal might be in a poor location for another, so be prepared to try multiple locations and testing each thoroughly before committing to a drill.

If channels 7, 9, and/or 13 are giving you problems, install the VHF reflector upgrade available at our website (Accessories > Reflectors).