I purchased my cameras from rearviewsafety.com. I have a 40ft fifth and the wireless didn't work very well, their customer service was great. They shipped me a separate antenna for free which helped but not enough, I purchased a high quality extension cable through amazon and now the antenna is by the front cap, problem solved. I also have side cameras which really help especially on freeway lane changes and backing up. They are mounted just in front of the propane doors and transmitters inside by the tanks. Great signal on those cameras.
Steve-