Radio Circuit Diagrams

FM Bugger Circuit

We are aware that an FM bugging device is a tool designed to transmit information from one individual to another in a remote location. Typically, bugging devices are employed to ascertain an individual’s activities, such as their whereabouts and the content of their conversations. Despite its illegality, many intelligence agencies exploit this vulnerability. This is a basic electronic circuit that enables you to eavesdrop on someone’s conversation over a considerable distance by utilizing a standard FM radio receiver. The FM bugging circuit is discreetly placed in the room where the conversation is to be intercepted, and the dialogue can then be intercepted and listened to using a standard FM radio receiver.

FM Bugger Block Diagram:

FM Bugger Block Diagram


The message or conversation signal is subjected to modulation through the utilization of the carrier frequency produced by the tank circuit, as depicted in the block diagram. Subsequently, the transistor carries out modulation on both the message and carrier signals before dispatching the resultant modulated signal via the antenna. This modulated signal is captured by the receiving antenna and subsequently relayed to the FM radio, enabling the user to engage in listening to the conversation. To effectively capture the transmitted signal, the user needs to adjust the receiver frequency on the radio accordingly.

FM Bugger Circuit Diagram:

FM Bugger


FM Bugger Circuit Explanation:

  • The circuit uses analogue modulation in which the carrier signal is applied continuously to the message signal. Here, in our circuit, the conversation of people is received by the MIC and give to the circuit is modulated to the carrier signal and transmitted.
  • There are various types of analogue modulation, including amplitude modulation, which includes single side band (SSB) and double side band modulation, and angle modulation, which includes frequency modulation and phase modulation. FM modulation is employed in this circuit. The carrier signal’s frequency is modulated according to the modulating signal’s instantaneous amplitude in FM modulation. When opposed to amplitude modulation, normal FM radio uses this sort of modulation to convey their messages. Frequency modulation has a higher throughput and efficiency.
  • MIC is placed in the room in which you want to listen to the conversation of the people and MIC will decode the conversation in to the signal which is given to the capacitor C1 where C1 is used for removing the noise in and turn on the transistor.
  • The tank circuit (capacitor C6 and L1) which produce the carrier signal for the conversation or message signal, the transistor will amplify the both the signals and send to air through the antenna. The capacitor C4 is used to remove the noise in the transmitted signal.
  • The capacitor C6 is variable because you can adjust the capacitor for producing your own carrier signal. Remember carrier signal should be in range of 88 to 105 MHz so that FM radio receiver set can receive your transmitted signal.
  • The FM radio receiver set is adjusted your frequency for listening to the conversation.


  • You can make L1 using about 25cm length of 25SWG wire. Wrap the wire around a cylindrical object of 6mm diameter and take it out after eight turns.
  • The transmission area range is around 100 meters.
  • Check whether the oscillator circuit is working properly or not before transmitting.
  • You can use a dipole antenna for transmitting the signal to increase the range of the transmitter.
  • Circuit operating voltage is around 3V, you can use a battery of 3V or normal DC supply as the power supply.
  • For better working use the PCB board for soldering or connecting the components in the circuit.
  • This circuit can be used in offices, colleges or any where you want remember bugging is illegal.



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