You will not get a signal parked under a tree but it you are on a budget than mounting a home style antenna on a tripod is a great choice. You get the exact same home service as a much lower price and you can run a long coax cable to located the antenna in a clear spot while the RV remains under the trees.
It takes a bit of time to learn to manually point the antenna at each new location but 3-5 times setting it all up will make it very understandable. There are a number of apps available for your phone that can give you the correct direction to point the antenna and the correct elevation, azimuth and skew required for proper reception. Plan on spending $200+ for a really good antenna/tripod setup.
