So, I went to investigate how drones transmit video! They use FPV modules/systems (first-person video). Many use 5.8Ghz. So they might use 200 milliwatt, 5.8GHz module to transmit video 2.4km range. Or 800 milliwatt for 4.8km range. Note that drones broadcast an omnidirectional radiation pattern, using circularly polarized omnidirectional antennas on transmitter and receiver. We don't need that for the robots, since we are in just one direction from them. Maybe we could use cast surface grid antenna, or dish antenna, on the base stations and robot stations?

I've found a video intro to FPV, and antenna type, dbi/gain, power, diversity controllers, here! 

Remember, like I said, the robots can use a narrow beam vs. omnidirectional that drones need - so we can get much better range without same power costs. The idea of a diversity controller is quite interesting! We have this attached to the base station. It would have different antenna on it, and it will select the antenna getting the best signal. This is the one it would switch to the base station. So it could have a circular polarised antenna on it, and a dish antenna, and a patch antenna, and it will select which is getting the best signal! Drone users are making even 6-channel diversity controllers! Something I'll look into! The next step up for drones, is to use motorized tracking antenna that will point at the drone. These can give up to 115km range for video transmission e.g. http://www.uavfactory.com/product/86 !!