rear view/back up camera erratic

I am new here so I may be in the wrong forum but here is my question. My wireless rear camera goes on and off while driving on the open road. When I go under a bridge it stays on. The antenna is below the roof on the back of the travel trailer. Could the problem be the back of the trailer is blocking the signal. The trailer is 30 feet plus 8 foot truck bed and the distance to the dash camera. Do I need to raise the antenna above the roof? The side cameras work good all the time.
Thank you, Bill