If you are simply trying to get reliable reception while parked, you'll want to create a TV Fool report. Here is how to get started,
http://forum.tvfool.com/showpost.php?p=6
Reliable reception starts with the antenna and it's correct placement. Amplifiers, also referred to as 'boosters' are only able to overcome signal loss in the cable and splitter that is connected to the output of the amplifier. In an RV, the length of cable is usually so short that an amplifier makes no sense, particularly when you consider that amplifiers also add noise and distortion to the signal. If you have only 1 dB of loss in the cable and the common amplifier adds 2 to 6 dB of noise, your net result is a lower quality signal at the TV.
Please consider generating a TV Fool signal report and posting the link so we can see what your signal conditions are like. We'd be glad to offer a suggestion or two based on the actual conditions you're dealing with.