2nd what Skeeve says +
Most if not all video links will be in the microwave band, i.e greater than a Ghz.
The range will be dependant on the frequency and power used. You are unlikely to get more than a few Kilometres with existing (cost effective) equipment. You will also have to use directional antennas to maximise reception. The receive ground station will also have to have line of site coverage to the aircraft.
All possible (the police routinely do it) but theres no cheap way of doing it.