Type 1- Long range DIY FM transmitter with 3 transistors and 3 inductors


  • Long-range FM transmitter: 100m-500m. Tested several times by BuildCircuit team. 
  • Transmit your voice to your FM radio in the range 88-108Mhz.
  • Transmit voice or music.
  • Can be used as a bug FM transmitter
  • Adjust the frequency and volume.
  • Handy and small.

This is a DIY kit. You will get all the parts required to build this FM transmitter. 


WARNING: BUYING and USING an FM transmitter is illegal in several countries. Make sure that it is legal to use in your country before you place an order. 


 If you are in Australia, you can order one of these three FM transmitters:

  1. DIY FM transmitter with a battery holder
  2. DIY Mini FM transmitter without a battery holder
  3. Basic DIY FM transmitter with 3 transistors

Transmission Range: 100m-500m

This is one of the most powerful do-it-yourself(DIY) FM transmitters BuildCircuit has ever tested. It can easily transmit audio signals up to 500 meters. It is a do-it-yourself (DIY) kit. Basic soldering skills should be enough to build this transmitter and it works perfectly on the first attempt. Unlike other FM transmitters sold by BuildCircuit, it has  3 transistors and 3 inductors which makes it very powerful.

This FM transmitter has a volume controller. Supply voltage: 3V-9V.


  1. Transmission range: 100m-500m (depending upon antenna length, test environment, power supply, and FM receiver )
  2. Audio and voice transmission: Transmit both audio or voice. The audio signal can reach 100m-500m depending upon the antenna of the receiver and used environment. For example, if you transmit from a higher building keeping the antenna by your window, the signals easily reach up to 500m. It is highly recommended that you test the transmitter in the open ground/space where there are no buildings or any other obstacles.
  3. First test: You can test the transmitter immediately after you assemble it. You can use any general FM radio
  4. Frequency range: 88Mhz-108Mhz.
  5. You can adjust the frequency.
  6. You can adjust the volume using the potentiometer.
  7. Antenna: if you use 20cm wire as an antenna, it can transmit up to 100m. With 40cm, it can transmit up to 200meters and with 60cm long antenna, you can transmit up to 500 meters.
  8. Operating voltage: 3V-9V. We have tested using a 9V battery.
  9. Operating Current:3.3-29mA
  10. Audio Response:20Hz-15KHz
  11. Radio Frequency Power:-2dBM~15dBm
  12. Radio Frequency Output Impedance:50 ohm
  13. Board Size:50*30mm
  14. The Second Harmonic:>=-40dB
  15. Receiver Devices: General FM radio/cellphone which has FM radio function/Car FM radio(Recommended for testing)

Assembly video: 

 Components included:

  1. R7 – 1 x 300R (Orange-Orange-Brown)
  2. R3- 1 x 1M Ohm (Brown-Black-Green)
  3. R8- 1 x 100 Ohm (Brown-Black-Brown)
  4. R4, R5- 2 x 10K Ohm (Brown-Black-Orange)
  5. R1, R2- 2 x 4.7K Ohm (Yellow-Violet-Red)
  6. R6, R9- 2 x 47K Ohm(Yello-Violet-Orange)
  7. C3, C4- 2 x 0.001uF capacitors (Code-102)
  8. C10, C14- 2 x 15pF (Code- 15)
  9. C15, C16- 2 x 47pF (Code- 47)
  10. C11, C12- 2 x 30pF (Code- 30)
  11. C1, C2, C5, C6, C7 – 5 x 0.1uF capacitor (Code: 104)
  12. C13- 1 x 200pF (Code- 201)
  13. C9- 1 x 24pF
  14. 1 x Electret Microphone
  15. 1 x 3mm RED LED
  16. L1- 1 x 4T inductor
  17. L2- 9T inductor
  18. L3- 8T inductor
  19. 1 x 5P Audio Socket
  20. 1 x Ceramic adjustable capacitor (use this to adjust frequency)
  21. 1 x 10K potentiometer
  22.  1 J2 – Screw terminal for connecting a battery
  23. Q1- 1 x S9014 transistor (be careful, don’t replace S9014 with S9018)
  24. Q2, Q3- 2 x S9018 transistor (be careful, don’t replace S9018 with S9014)
  25. 1 x PCB

What do you need to arrange yourself ?

  1. Stereo audio cable- to connect from an audio source to the transmitter.
  2. 9V battery connector or any other kind of battery holder to power up the transmitter
  3. Antenna- You can use any 1-2mm thick wire for antenna
  4. 3V-9V battery
  5. Any FM radio with telescopic antenna.

Didn’t work? This is how you troubleshoot.

  1. Check the transistors: There is a high chance that you soldered the transistors in the wrong spots. There are three transistors and all look the same. Make sure that you soldered S9014 and S9018 in their right spots. Check here.
  2. Look at the back of the PCB, make sure there is no short.
  3. The electret microphone polarity could be wrong.
  4. The battery connector could be connected incorrectly.
  5. The 103(10K)potentiometer could be turning off the volume completely.
  6. Resistors soldered incorrectly.
  7. Check the polarity of 3mm LED.

If the transmitter is working, you would get feedback from the FM radio.


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