This is the most simple FM transmitter circuit diagram you can ever find. This circuit is really cool and cheap to build.
This FM transmitter circuit runs at low voltage, on a CR2025 3V Lithium battery, current consumption is also low.
And the total size of this F.M transmitter(including battery, excluding antenna) is less than that of a matchbox.
Simple FM transmitter circuit diagram
The circuit has a central RF oscillator NPN transistor BF494 (substitute: BF194). A coil takes care of the output frequency. The coil has to made by yourself. 36 SWG wire 2.5turns only in 5mm diameter ferrite rod.
Keep the circuit as small as possible. Try to use no wire in the main functional area(transistor and coil).
The input from the audio output of computer/PMP/mobile is given to the biased base of the transistor. The transistor gives a RF humming accordingly to the audio input, and the FM wave is spread by the external antenna(Ariel).
By using a standard T.V antenna, the range of this transmitter can go upto 1KM radius, using small(15-20cm) Ariel, it can work upto around 50M range. For even more low cost, use a new bicycle spoke for ariel, get it from cycle store at Rs 2/- .
This circuit is most suitable for miniature FM transmitter for use in computer, mobile etc to send music to home theater system without wires, and in homemade wireless walky-talkies.
For input from low power output devices, such as mobile, computer’s sound card, the value of the unlabeled capacitor is 0.1 or 104. For higher wattage outputs, the value is 0.01 or 103. You can add a microphone pre-amplifier in this circuit to transmit voice directly.
Keep in mind that this type of simple FM transmitter circuit are allowed for personal use. Commercial use of Radio frequencies (including FM) without permission is illegal in almost everywhere of the world.
Part list
- Transistor BF494 x1 3/-
- Resistor of various value(all 1/4 watt) x4 1/-
- Capacitor of various value(all 10V, small, ceramic) x3 2/-
- 36 SWG copper wire for coil 1 inch 1/-
Total 7/-
Others:
- input audio jack x1 3/-
- Ariel(stick antenna) x1 15/-
- Battery CR2025 x1 7/-
Cost in USD is, 0.2$
Pls tell me about some basics to built circuits and where do i get parts from its urgent i know some basic but cant be explained from ur blog
Ami ki ekhane bc547 use korte pari bf494 er poriborte?
Na, paro na.
hey Arup, thats great! I remember building an FM circuit like that when I was around 12 years old too...but that was 30 years ago in the early 1980's. I was amazed that it actually worked! It had a range of a kilometre or so. I took it to show the physics teacher at school, he had no idea how it worked but he was pretty impressed 🙂 Its good to see that guys like you are still experimenting with electronics.
Doug
London UK
ETATE COIL NA DILE MW DHORBE TAI NA.
AM I RIGHT OR NOT?
Hi,it is the c1,c2 is trime capacitor?
Hi,apur do u post the 56pf,47pf capcitor L1 diagrame
Hi,apur do u post the 56pf,47pf capcitor and L1 diagrame
Can i use BC 548 instead of BF 494 transistor?
Hi Arup can I use a variable coil and if I can, can I set the frequency with that variable coil?
is this transmiter circuit a frequency multiplier their working and circuit are similar
i need a simple fm reciever circuit please help me i am tired of googling am from ghana and rf spectrum laws are not street therefore i also need 70km transmitter circuit
this circuit really a bad one add feedback capactor to collector and other lead to emitter lead and replace 10k ohm with 4.7u capacitor this will let it transmit at narrow or particular frequency but if you want simple transmitter circuit contact me only four components 10km 0.7A at 1.5v frequency range depends on transistor frequency from 5kHz to limit and would to be your friend if don't mind
or just add filter circuit to the rf output to allow only one rf current to reach the antenna its only two components(LC) in series
for LC values for particular frequency use their impedance or resonant frequency formular