200M FM Transmitter
Description.
A very stable and simple FM transmitter circuit is given here. With a matching antenna, this transmitter can attain a range of around 200 meters. I assembled this transmitter few years and got very good results. Let us see how the circuit works.
A condenser microphone (K1) is used to pick the sound to be transmitted. Capacitor C1 is a DC decoupler and the sound signal is coupled to the base of Q1 which wired as a preamplifier.R2 and R3 are the biasing resistors of Q1. Amplified sound signal will be available at the collector of Q1 and it coupled to the emitter of transistor Q2 through the capacitor C4 and 1mH inductor L1. Capacitor C4 decouples the DC component from the preamplifier output. Q2 performs the job of oscillator and modulator. Inductor L2 and variable capacitor C5 forms the tank circuit necessary for creating oscillations. Capacitor C6 is the feedback capacitor. The modulated FM wave will be available at the collector of Q1 and it is transmitted using the antenna A1.
Circuit diagram.
Notes.
- Assembling the circuit on a good PCB will give better results.
- I used a 12V battery for powering the circuit. A 9V PP3 battery will also do the job.
- A battery eliminator is also fine but it will induce noise.
- Antenna A1 can be a 25cm long copper wire.
- K1 is a condenser microphone.
- C2 should be a Tantalum capacitor.
- Variable capacitor C5 can be used to adjust the transmission frequency.
- This simplified formula will help you in making inductors, L = (d²n²) / (18d+40l). Where L is the inductance of the coil in uH , d is the coil diameter in inches, l is the coil length in inches and n is the number of turns. Just try to make the inductor your self using this formaula. If you can’t, then comment here.I will give you the winding details.
How to calculate the frequency of this fm transmitter and how to make inductor coil of 0.1uH please suggest some methods to make inductor coils
good one but i want that winding details….. can u please help me…..
Hi, now i’m in Cambodia , some comnponent not easy to find but i want to buy online can u tell me where to buy (website)
@ Suraj
Try this link
http://www.circuitstoday.com/how-to-make-an-air-core-inductor
Could you Plz tell the o/p frequency of the transmitter.
i.e. at which frequency I could be able to get the signal in my FM Receiver.
Plz Its URGENT.
De 18 and 40 are they constants. How do i increase the output power of my transmitter
How to calculate the frequency of this fm transmitter and how to make inductor coil of 0.1uH please suggest some methods to make inductor coils
@ Hardik
Try this link – http://www.circuitstoday.com/how-to-make-an-air-core-inductor
How to create inductors?
@ Dinesh
Try this link – http://www.circuitstoday.com/how-to-make-an-air-core-inductor
thank you . kheily khob bood.
امیدوارم موفق باشید.
What is the frequency range? I assume C5 is used to alter this?
sir can i make that inductor L3 by my own pls suggest….
sir tell me about how many turns required for 1mH & 0.1uH Intductors for 200m fm Transmitteralso about the thickness of wire plssss its very urgent………….plsssss ?????????????????????????????
ya…. its very interesting.. but at wat frequency i can receive my message..