Welcome to the forum !
Not sure what to tell you if you have a stock Vision as mine has an aftermarket gimbal and one antenna is covered by it in the camera .
I had one and got beteen 3000' to 3500' with my set up but like I said never tried it with just a stock Vision . You can get out lower with it
but maybe you can find more info here http://www.phantompilots.com/threads/itelite-antenna-owners-thread-4-miles-with-p3p-page-31.31622/
Good luck