rear-facing traffic cameras on caravans

I've microwaves on a rear-facing camera for years. Great advantages, including seeing the car tucked in behind you, and seeing the front of the lorry you've just passed, to know when to pull in, plus seeing well back when you're planning to overtake. PROBLEM; the camera broadcasts to the car, and the signal is easily over-ridden by microwaves ovens nearby, etc  .SOLUTION ? Anybody know of a system that cannot be interfered with (other than cable linkage to car)?