Simplest Fm Transmitter!
This is the simplest fm transmitter circuit you can ever find on internet,because so many “simple transmitters” (they call it simple but many of them don’t work!) on internet will not work as those circuits are designed poorly. i had built around 100s of transmitters in the past and most of them were built successfully, because the design is just cool and reliable. This circuit is for those who have built many fm transmitters without any sign of working!, so try this one and i am sure you can make it!.
What is an FM transmitter?
An Fm transmitter is a circuit/device to transmit audio signals to an fm radio receiver through air (wirelessly). The input (audio)to an fm transmitter can be fed using a microphone or the output of your music player to be transmitted, and the signal which you transmit can be received using an FM radio, the advantages of FM TRANSMITTERS ARE many:
1.You may transmit audio to another room/floor of your house without using any wires!
2.You may transmit your own voice if you used an electret microphone in the circuit
3.You don’t need to build a receiver to receive the ransmitting audio as any standard fm radio can be used to receive your voice/audio and many..!
building the circuit
this circuit can transmit audio to a distance of around 50 meters if you used 2n3904 transistor and boost the supply voltage to 6V, and 1Km(1 kilometer) if used S8050 transistor with 9V supply!
Components you need
R1 – 47K resistor
R2 – 100 ohms resistor
C1 – 22n none polarised capacitor
C2 – 1n none polarised capacitor
C3 – 4.7pf none polarised capacitor
c4 – 22n none polarised capacitor
T1 – Transistor BC547(short range),2N3904(medium range,recommended),S8050(long range)
VC1 – 22pf Variable trimmer capacitor (trimcap)
L1 – Aircore inductor, 6turns on a 3mm dia former eg.Wind over a pen refill.
Antenna – a short length wire
3V battery (Use only battery)
Good quality pcb or veroboard. (breadboards may not work)
after building is done,power the circuit using a 3V battery and connect any audio source to “audio input” pin properly, set an fm radio minimum 3 meters away. Start tuning the radio and tuning the VC1 at the same time untill you receive the transmitting audio, if you can hear the audio then you are DONE!.
1.All components in the circuit is not intended to change their values
2.Using correct value components in the circuit is vital
3.If the transmitting audio is too loud and unclear, then add a 100K or 1 Mega ohm resistor across the audio input pin, the value of this resistor depends on how much powerful you audio signal is and should be selected untill you get a very clear voice.
The circuit has been tested by me with great results!