Rf receiver

I'm working on a simple receiver circuit. Just to receiver a 27MHz signal to drive a motor. This is how the circuit goes..

Tuned circuit ----> Amplifier ----> halfwave rectifier ---> transistor as a switch to drive the motor

When i only tested the motor circuit itself... just using a 3V battery to run it... it doesn't... but when i use power supply of only 2.18V it runs...

anybody can explain? because of its current?

Could be related to the bias of your amplifier. Try to tune the idle bias of the amplifier for different supply voltages until is working, for the DC range that you are interested.

power supply can provide more current,more power, can the battery provide current enough,so y should test your circuit how much current it need!