RF Detector Based on Transistors

This rf detector circuit diagram is designed based on transistors and common electronic components. This circuit responds to RF signals bellow the standard broadcast band to over 500MHz and provides an visual, and audible indication when the rf signal is detected. 
RF Detector Circuit Diagram
 
By adjusting the bias of D2 with the R2 potentiometer the circuit can detect low power or strong signals . A very sensitive setting can be obtained by modifying R2 until the LED begins to light . If the rf detector is not enough sensitive you can connect a good wideband RF amp between the antenna and the detector diode .

Keep diode and capacitor (C1) leads short to minimize stray inductance. The used transistors can be: 2N3906 ,2N2907 or other PNP high gain transistor for Q2 and PN2222A , 2N3904 or other NPN high gain transistor for Q1 .