FM transmitter circuits / projects because some times the transmitter is working but not broadcasting on the desired frequency due to which we can not confirm that the circuit is working or not. Therefore by using this circuit we can quickly confirm that the circuit is actually working but not broadcasting on the desired frequencies. As the circuit is a wide band RF detector therefore it can be used for testing many other RF circuits projects you build. The circuit is using only few components which are two diodes OA91, two transistors, one 10K resistor and a buzzer. You can also use any other similar germanium diode in the place of OA91. For good performance use 30 inches telescope antenna.

Working of the circuit
Working of the circuit is simple when the two OA91 germanium diodes receive an RF signal then they convert it in to DC signal. This DC signal is further amplified by the NPN transistor 2N4401 and sends it to the base of the 2N4403 PNP transistor hence making it switch ON and activate the buzzer.

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Like field strength meter an RF detector circuit is also a useful project to detect RF signals. The circuit shown here can be used to detect wide band of RF signals and provide an alarm when it will detect an RF signal. The circuit can be very useful for electronic students who make Radio frequency and

RF Detector Circuit Schematic