Having tried to pick up OTA (off the air) TV for 13 years, I've found that in the western deserts, I can often pick up stations up to 50 miles away. In the hilly, grassy, cornfield midwest, 35 miles is about it. In the forested east coast area, 25 miles is about it. In all these cases, that's the best range, and it's often local conditions that shorten that range even further.
I've been places where I was 8 miles from the transmitter and couldn't get a signal. One time in Flagstaff, parked in a RV park at the base of a giant hill, I could not pick up a station even though there were several station antennas on top of that hill. That I could see from my RV. Lucky that RV park had cable. Stayed in 2 RV parks there in Flagstaff and the pine trees, or power limitations, or directional transmit lobes, played havoc with the strength of the OTA TV signals. Even when you could see the transmitting antennas on the hill off in the distance.
I did upgrade the standard antenna to a 'fringe' high gain style, but there was no change at all. I knew exactly where the transmitting antennas were, had my old antenna set up for them, and was missing 2-3 networks. Installed the new, high gain antenna, and was still missing 2-3 networks. HAH! Waste of money, effort, and time.
So, I'd say, don't bother pouring much money into equipment without being in a place you can actually test, or without having a generous return policy by the seller. I did break down and go with satellite back in August, also went with the DNS (Distance Networking Service, $20/mo extra) program so I get the big 5 networks from LA wherever I am in the satellite footprint.
Good luck, and note if you plan on driving around the country, there's many places you just won't have OTA TV, and those places usually the RV parks supply free cable TV.
