RE: Range, Futaba
I have never flown past 2500 feet. It may be possible but I do not want to try it. We always say if you can see it you can control it which is true for a .60 size plane. I don't think I would want to try it with a 40% Extra though.
I would think that a design that transmits on as narrow a bandwidth as possible would theoretically transmit the farthest, less splatter. 6 mhz for video and sound.
I believe many of these less expensive systems transmit over a broad 50 mhz bandwidth or more.
Think of it as a water hose and pressure. Put a 1" nozzle on the hose and 50 lb. of pressure (mw),
Then put a 1/4" nozzle with the same 50 lb. (mw). Which one will transmit the water or signal farther?
The same goes for antennas. A very directional yagi antenna will positively increase range but that would not be practical. All antennas must be properly impedance matched to reduce standing waves or else you don't transmit the power it bounces back to the output and ends up as heat.
All of this could be bull, maybe we can have an expert tone in.