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$
For direct trnsmting the voice ..we hv to use amplfr with mic.. This increase the size.
The preamplifier circuit for microphones is also simple. See here.
sir i want to know if bc457b transistor would work too ...and thanks
I am a sat. engineer working with DAAR Groups , a satellite firm in Nigeria with a bureau in Ghana. I think I like your work and it is so nice and precise , thanks.
on which frequency the signal is transmitting.?
Value of unlabeled capacitor, is it pf or micro frd ???
It's 0.01uF. 0.1uF can be used also.
Is it possible to modify the ac cfl circuit to dc circuit
What are you talking about in a page of FM transmitter? Anyways, AC CFLs work in DC supplies too.
dear arup can you please post the pin diagram of BF494
I did'nt gettin ur pin diagram....which one is colletor,emitter and base....is centre one is not base?
Can't you see the above image? The 1st pin is Collector, middle is Emitter and the right one is Base.
Hi! I want exactly the thing which u have presented and want to build this right away.But my concern is how stable is this circuit? I have seen circuits more complex but very unstable and difficult to tune up with even a trimmer cap.
Simple circuits like this one will not give you the best stability and results.
if we want to increase the transmitting range.. as u said above the range is 50m ...if we want to increase it to 2km what is te circuit modifications...pls help me..
You need much more complex circuit for that.
Arup da,
Mobile er fm reciver ba digital fm reciver diye ei sob fm transmitter(single transistor & lc oscillator) er brodcast kokhonoi dhora jai na keno??
kintu gang lagano reciver a sona jai keno??
Karon oi digital gula different technology use kore. Ogula direct spectrum scan na kore, kono type er interpolation kore channel dhore.
dear all friends
kindly requesting send & give me a modified good effective transitor tone control circuit (indian available components)and modified la 3161 head pre circuit for me normal circuit i have i need modified (quality increased matching circuit with all changed values) for using with any amplifer,if any friends have plz send scanned mail to
thanks regards to all friends
iqu
hi is there a jump between the base of transistor and the two resistors?
No. It's connected.
good work
Thank you.
Hi arup what is the transmitting frequancy
It's adjustable and depends upon the capacitor and mostly on the coil.