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FM Telephone Bug

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  • Nicolae Sfetcu
    FM Telephone Bug ... Here is a simple transmitter that when connected to a phone line, will transmit anything on that line (execpt the dial tone) to any FM
    Message 1 of 2 , Sep 30 11:40 PM

      FM Telephone Bug


      Here is a simple transmitter that when connected to a phone line, will transmit anything on that line (execpt the dial tone) to any FM radio. The frequency can be tuned from 88 to about 94Mhz and the range is about 200 feet. It is extremely easy to build and is therefore a good, useful beginner project.

      Schematic


      This is the schematic of the phone transmitter

      Parts


      Part
      Total Qty.
      Description
      Substitutions
      R11180 Ohm 1/4 W Resistor
      R2112K 1/4 W Resistor
      C11330pF Capacitor
      C2112pF Capacitor
      C31471pF Capacitor
      C4122pF Capacitor
      Q112SA933 Transistor
      D1, D2, D3, D441SS119 Silicon Diode
      D51Red LED
      S11SPDT Switch
      L11Tuning Coil
      MISC1Wire, Circuit Board

      Notes

      1. L1 is 7 turns of 22 AWG wire wound on a 9/64 drill bit. You may need to experiment with the number of turns.

      2. By stretching and compressing the coils of L1, you can change the frequency of the transmitter. The min frequency is about 88 Mhz, while the max frequency is around 94 Mhz.

      3. The green wire from the phone line goes to IN1. The red wire from the phone line goes to IN2. The green wire from OUT1 goes to the phone(s), as well as the red wire from OUT2.

      4. The antenna is a piece of thin (22 AWG) wire about 5 inches long.

      5. All capacitors are rated for 250V or greater.

      6. The transmitter is powered by the phone line and is on only when the phone is in use. S1 can be used to turn the transmitter off if it is not needed.

      7. If you have problems with the LED burning out, then add a 300 ohm 1/4W resistor in series with it.

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