simple FM transmitter

Here, is a very interesting and simple project in the series of communication used to transmit noise free F.M. signal in the wide range up to 100 M using only one transistor. The transmitted message from F.M. transmitter circuit is received by the receiver having the facilities of F.M. channel or you can also try F.M. receiver circuit published in this website.

Circuit Description of simple F.M. transmitter

The entire circuit of F.M. transmitter is divided into three major stage i.e. oscillator, modulator and amplifier. The transmitting frequency of 88-108 MHz is generated by adjusting VC₁. The input voice given to microphone is changed into electric signal and is given to base of transistor T₁. Transistor T₁ is used as oscillator which oscillates the frequency of 88-108 MHz. The oscillated frequency is depended upon the value R₂, C₂, L₂ and L₃. This transmitted signal from F.M. transmitter is received and tuned by F.M. receiver.

PARTS LIST

Resistors (all ¼-watt, ± 5% Carbon)

R₁ = 180 KΩ

R₂ = 10 KΩ

R₃ = 15 KΩ

R₄ = 4.7 KΩ

Capacitors

C₁ = 10 KPF

C₂ = 10 PF

C₃ = 20 KPF

C₄ = 0.001 µF

C₅ = 1 µF/10V

C₆ = 4.7 PF

C₇ = 10 KPF

C₈ = 3.3 PF

VC₁ = 22 PF

Semiconductor

T₁ = BF194B

Miscellaneous

MIC₁ = Condenser mike

L₁, L₂ = 3 turns of 22 SWG wire around any thin pencil

L₃ = 2 turns of 22 SWG wire around any thin pencil.