So I have been searching around the internet on information regarding using SDR for radio receiver and transmitters for the control of one's quadcopter or multirotor device. Any thoughts or if anyone has done something with this? Just a thought as my two next hobbies are SDR and multicopters.
I don’t see any real reason to combine SDR, either TX or RX, and control of the mutlicopter, commercial OTS TX and RX is fairly inexpensive and capable, as well as compact and optimized.
However, that does not mean that SDR and RC cannot be used together in other ways than flight control. A buddy of mine has a Raspberry Pi based SDR wireless streaming rig, just the Pi, a hub, and the RTL SDR. We put this on my quad rotor and got some interesting results. We essentially were able to place the antenna (and SDR) several hundred feet up with no coax loss

It could be very interesting to play with a Doppler based DF system and link the results back down to a ground station. Might make Fox hunting interesting.
T!