BC516 that has more gain as compare to the 2N4403 transistor.
The circuit is using two 1N34 germanium diodes which can be replaced by any other similar germanium diodes. For good performance use a 30 inches telescope antenna. The circuit can be powered by any 9 or 12 volt battery. 

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Here is an improved version of the RF detector circuit that we have discussed previously.  The sensitivity of the circuit is almost double as compare to the old circuit. In the previous circuit we have used a 2N4403 transistor to activate the buzzer but in this circuit we have used a PNP darlington transistor

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RF Detector Circuit (Improved)