hi dave
2.4 uses very similar technology to bluetooth in mobile phones, the transmitter and receiver lock togeather using a fixed frequency band this removes glitches, as the reciever will only answer to that transmitter. no crystals are used in any 2.4ghz sets. im new to robots but not rc my advice by good ie spektrum or futaba with built in model memory and mixing saves lots of time, jumping motors and small mixing units in the robot