Hai friend, you can simply make any voltage from a greater source than you need, so it need only a power transistor, and a zener diode with a resistor. the output voltage is determined by the voltage of the zener diode you used.so from a 12 volt , source you can tap from .3 volt to 5.3 volts..7 volt will drop because of the junction barrier of the transistor. but in my experience its better to connect a reciever with an individual battery pack, if not it can generate some SAW problems with operating waves,can cause lack of control and crash.