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    Take a look at this fm spy transmitter which can be used as a bug transmitter or as diy fm bug too. It uses a single IC 74F13, one coil, a capacitor, one trimmer, one resistor and ofcourse one electret mic. This spy bug is so easy to build and can give you a total coverage range of about 3 to 5 meters. You may want to use a small 100mW amplifier to give a little extend transmission range so you can spy from other location.

    Please use only 74F13 because 74S13 and the other ones does not work in 88-108MHz range. As antenna you can use a copper wire (>=1mm diameter) and as power supply 4 x1.2 / min.1200mA acumulators which will work for at least 7 days. Use short terminal for components and a good pcb.

    Mini DIY FM bug | spy transmitter circuit

    74f13 fm bug spy transmitter

    ask a question

    14 Responses to "FM Bug Spy Transmitter Circuit"

    1. how many turns is the coil?

    2. Thanx marius

    3. Akingbade olugbenga says: on November 13, 2009 at 2:58 pm

      thev three capacitors are they 1nf or 1mf ,33nf or 33mf or 33pf , 100nf or 100mf pls i need help

    4. hello..

      for this circuit, how about the receiving end? does this circuit transmit at specific frequency? thanks

    5. If i add a diagonal pair of BC548 transistors as a amplifier then would it extend range ??

    6. The schematic has no pin number for the input from the microphone capacitor.

      Secondly, pins 1,2,3,4 are NAND gate inputs and pin 6 is the output for the same NAND gate which are all connected together. Is this correct ?

    7. does it work properly?

    8. which ic is it?? multiplexer or schmitt?? there are a variety of ic in market with the same number and me confused which to buy. plz advc

    9. how can i use 3.5mm jack to give the input to this circuit

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