How to make FM transmitter circuit
What is FM transmitter circuit
The FM transmitter (Frequency modulation) circuit is made up of a single transistor or a BJT. In wireless communication, the (frequency modulation) FM carries the data or information by changing the frequency of the carrier wave as per the information or a message signal.
The FM transmitter achieves the application of (very high frequency) VHF radio frequencies of 87.5 HZ to 108 MHZ in both transmission as well as in reception of the Signal. The FM transmitter completes the most excellent volume within less power.
The performance and working of the FM transmitter circuit is dependent upon the variable capacitor and inductor. In this article, you are going to learn that how you can prepare a FM transmitter circuit and how does it work with its various applications.
Things you must know about FMÂ Transmitter
The FM transmitter is a circuit that uses a very low power to operate and does uses (Frequency Modulation) FM Waves to transmit the sound. With the help of such FM transmitters we can easily transmit the audio signals through the carrier waves with different frequencies.
The frequency of the carrier wave would be the same as for the audio signal with an amplitude. The FM Transmitter produces a range of VHF from 88 HZ to 108 MHZ.
Block Diagram for FM transmitter circuit
Components required for FM transmitter circuit are modulator, oscillator, RF-Amplifier, Audio pre-amplifier, microphone and antenna. The Diagram shows the Block diagram for FM transmitter circuit. There are two types of frequency in the signal :
- Carrier signal (with carrier frequency)
- Audio signal (With audio frequency)
The carrier frequency is obtained by modulating the audio signals. The (Frequency Modulation) FM signal is obtained by differentiating the carrier frequency and by allowing the Audio frequency. The transistor is used for oscillator purpose in order to obtain Radio Frequency signal.
Working of simple FM Transmitter Circuit explanation
The circuit diagram shown for FM transmitter circuit and the electronic components are the resistor, capacitor, trimmer or variable capacitor, inductor (coil), transmitter, mic, 9v of power supply or 7809 Voltage regulator (in case if you are using input voltage more than 9v) and an antenna. The mic or a microphone is assumed to grab the sound signals and there is a presence of sensor with capacitance value inside the mic. The change in pressure of air or AC signal causes in production of such capacitance.
The Oscillation circuit could be made with the help of Transistor 2N3904, Inductor and the variable capacitor. The Transistor 2N3904 used in FM Transmitter Circuit. It is a NPN transistor which is basically used for signal and voltage amplification purposes. If the current is passed through L1 Inductor and the variable capacitor, the FM Transmitter Circuit will start oscillating with the resonant to that of the carrier frequency (I.e frequency of the carrier signal).
The negative current or the negative feedback will result C2 Capacitor to the Transmitter Circuit. The oscillator is required in FM Transmitter Circuit in order to generate the radio frequency carrier waves. The transmitter circuit is capable of storing the energy for the oscillation as it is a derived from the (inductor and capacitor) LC circuits. The audio I.e input signal obtained from the mic is passed through the base of the transistor in order to modulate the output signal of the LC circuit in FM (I.e frequency modulation wave) Form.
Here, the main purpose of the variable capacitor becomes that to vary the resonant frequency in order to obtain the best FM Signal Frequency band. The modulated signal is then transmit or radiated as a radio wave with the frequency of FM frequency range. The antenna is nothing but a piece of good conductor, in our application we’d used a copper wire of 30cm long and 26 gauges thick. You can use copper wire up to 25-27 inches long as an antenna in the circuit, the length of the antenna however must be significant.
Application of FM Transmitter Circuit
- FM Transmitter Circuits are used in a sound system as a signal transmitter.
- These are used in wireless components for vehicles and offices.
- The circuits are used to make FM transmitters used to reduce the noise in certain places.
Advantages of FM Transmitter Circuit
- The FM Transmitter Circuit could be made very easily as the very common components are used which are very cheap and easily available.
- Above circuit gives the very high efficiency in transmitting signal in a shorter range.
- The circuit is best suited for demonstration and fm transmitter circuit project.
- The circuit does have a large and complicated components.
- The transmitter circuit is capable to neglect the noise signal through the amplitude variation.
Disadvantages of FM Transmitter Circuit
- In above FM Transmitter Circuit, there is a large wider channel needed.
- With the Circuit, the transmitter as well as the receiver tends to become more difficult.
- The received signal gets poor quality as there an interference occurs in the medium.
- The above circuit is not good enough for high power fm transmitter circuit purpose.
After making the FM Transmitter Circuit you will be able to understand the basic working and application of the transmitter. Hope the article helped you. Feel free to share about how do you like or your queries in a comment below.
114 thoughts on “FM transmitter circuit with 3km Range”
Hi, I read your blog on a regular basis. Your writing style is awesome, keep up the good work!
Thanks Nick, I appreciate that !
I wish, to own fm transmitter with mic with freq Preadjust what shall be price at least some kilometre range what shall, be price at if u use battery or power, bank system for charging it’s good 98xxxxxx08 whatsApp
That’s the best FM transmitter, Everyone can see and make it. 🙂
Glad to know that you’ve found that helpful.
What is the range of the circuit
would you mind if i tell you that practicing such kind of fm transmitter circuit is prohibited in certain countries
Actually transmitting radio wave without a government approval is prohibited in most of the places. However, you do can use the transmitter circuit in your projects and indoor applications. You will need to have a shorter range or fm transmitter.
i had made the fm transmitter as per your circuit, but i had to add a potentiate in the base of the transistor.
Please do make same for fm receiver which i can use in my car
We may publish a post on that. Thanks for your suggestion Kshitiz
is there any way i can know what frequency i’m using right now ?
well in this circuit we can’t define the frequency its transmitting. You can calibrate the variable capacitor in order to point at its corresponding frequency, However i do not see any way to just see the frequency which we transmit through it.
Isn’t it illegal to make and use such signal transmitting circuit ?
in my place it is forbidden
The post is just for educational purpose and to let you know the concept that how does fm transmitter circuit works. You can use it in another projects and applications which would be legal.
how can i use more than one mike in the circuit of fm transmitter you had shown ?
multiple channel amplifier may get the job done 🙂
can i use the fm transmitter circuit to transmit signal from my phone ?
yes, of course ! This was the thing i too thought at the first.
hi, i want to make high power fm transmitter circuit please help me
i want fm transmitter mini project, any suggestion ?
You can use the transmitter circuit in any short range radio wave transmission projects !
I wanted to see a video similar to your rest of projects for simple fm transmitter project above.
You can watch the video for the same fm transmitter circuit in the above.
is there any way to know what frequency is tuned in my FM transmitter circuit ?
Pardon me, but there is no such a way i know by which we can define the frequency of fm transmitter.
Use a Frequency Counter with aerial placed close to transmitter output. Been using one for over 40 years to determine operating frequecy of transmitters.
is there any way i can use variable resistor in the transmitter circuit?
Nice work !
Thanks Andrew 🙂
Nice work @ Engr Farhan Skeikh Ahmad. Is this really 3M transmitter? Great work.
any method to make fm transmitter circuit using ic ??
I was looking forward to make fm transmitter circuit using ic 555. Is it possible the way you did it with the help of a transistor ?
I wonder if i can make and sell fm transmitter circuit board. is i legal ? 🙂
I don’t think so..
can’t say weather if it would be illegal or otherwise..
Can you make one for me [email protected] , we talk
Nice Work! Well done
What modifications i need to make in the above fm transmitter circuit for the range of 10km ?
I want to purchase the project. Plz let me know the price.
we’re afraid that we can’t help you as we only provide project list and tutorials.
hey i just powered your fm circuit with my 5000 mah powerbank !
Nice ! How did it do ?
Is there any way we can use arduino to make fm transmitter?
Well if it is, We’re not aware of. It would be nice if you share it with us if you find it anywhere.
good job.
i need more details about it.
Thanks Joseph, We’ve introduced the video of the same circuit made by another person. 🙂
i need more details about it.
A video might help, You may take a look at it 🙂
I want to make an fm transmitter circuit using ic, is it possible ?
Look what did i found!
You can increase the antenna’s height and the range of the capacitor and make the fm transmitter circuit for upto 10 km!
yes, Increasing the antina length increases the transmission radius and the range of capacitor effects the range of frequency we get.
Can Anyone suggest me a fm transmitter design which would be be very stable and can hold a good amount of Watts output power ?
Also the transmitter must be very stable and touching it or placing high amount or metals near by would not effect its signal while transmitting.
Please suggest me a better circuit design.
What you suggest requires a complicated design. The transmitter circuit we’ve shown in the post is just for generic purpose. You can find plenty other high efficiency fm transmitter circuit on the internet.
i was looking for a simple fm transmitter circuit diagram. it helped with some variations in capacitor, thanks
Thanks Luna. Glad that helped you.
what are some important application on fm transmitter circuit other than transmitting signal for radio communication ? i’ve heard that they’re used in our appliances like home-theater etc.
Similar circuits are used in home wireless speakers and many more. However, those transmitter circuits are far advanced and complicated then the one we’ve shown you.
i am looking for a simple fm transmitter circuit diagram and its pcb design
How does the length and the thickness of antenna effects the noise in the above FM transmitter circuit ?
What is the difference between an amplifier and a transmitter in the fm transmitting system?
Sorry, can you be more specific ?
Hi, i just made the circuit in the video but it seems to bounce the signal. i need a Help simulating FM transmitter circuit
What does it mean by bouncing signal ? can you please elaborate ?
I live in Bolivia, its silly but i donot know if transmitting radio signal is allowed in my country or is it prohibited.
You need to ask this in better places like legal forums related to your region. That way you can get more precise answer.
Nice article
Thanks Alishba !
Which ic should i use for the fm circuit ?
You do not need an IC in the above circuit.. It is made up of very simple electronic components which you’ll easily find in the market.
Please read article/scheme
Can i use the same circuit for more than 10 KM of range ?
No, The circuit won’t be powerful enough to transmit the signal for that radius. It will require certain modification.
Hi i want to make an fm transmitter so that i can transmit the song from my laptop and guitar in all around my home. Also would that be legal ?
You can give the signal output (which goes to the speaker/headphones) as an input to the circuit. It will transmit the songs within the range .
Legal? try informing local!!
where can i get variable capacitor ? I tried searching them on my local shops but didn’t found any..
Try searching it on amazon, they are available there.
Aliexpress
try aliexpress or maybe better GOOGLE!!
Aliexpress has ‘m . I bought them there in various values.
Such low power transmitter gives a range of about 20
metres maxing out at 50 metres
Yep, Several meters. Would agree with that. 🙂
nope…… got it at 2.6Km line of sight.
You will in any case find that simulation is not usually all that useful with these kinds of circuits as they are far too sensitive to parasitics. I would suggest just dead bugging the thing on a bit of copper clad (use the copper clad board as the ground plane), but be prepared to be very disappointed about range, I am thinking a few meters at best.
Does this “FM transmitter ckt” give a fairly good audio quality at FM receiver ?
what about inductor gage
The article says that transistor 2N3904 is used for amplification purposes in ascillator circuit. But there is no such transistor in circuit diagram.
Please explain how to insert this transistor in circuit.
It is an equivalent….
Gud day ENGER pls how can I expand it up to100 kilometers
This is a VERY LOW power circuit. for 100KM you need serious gear…
Hi Alwin,
Of course, we need more power for the 100km range when compared with the 3km range circuit. You can try some linear amplifiers and experiment. Be enthusiastic and keep learning.
Thanks
EEE PROJECTS Team
Hi,
Good to see your interest, try doing it with the help of some linear amplifiers. Remember, the more you explore the more you learn.
Thanks
EEE PROJECTS Team
I like your blog
but ENGR. how can I extend the distance like 30km range..please help
Build a linear amplifier……Examples you can find on internet.
Please, can you help me use this transmitter as a remote control device rather than an audio transmitter ?
I been trying this so long and I have fail ,pls I need someone who will teach me , my WhatsApp no +234********75
Do u know how to build an rc transmitter
hi engineer ,how can I expand to 30km range
what about a tv station
thanks. Please I need tested and working Reciver circuit
Please help me understand the use of C2.
hi ,is there a strict relationship between capacitor VC1 and C2 ?? i need to know so i can have more control of the output
I would also need to have My radio station now i don’t know how to go about it. I’m a Zambian.
what would i need to change if i would add a aux jack instead of the mic
Wow,can it be use as a transistor in a cardboard car?
Hi,
just a small question
from the value of L and C
we should get around 50.329MHz right ?
how much Transmit Power on it ?
Do u have any calculation for this one?
when talking in the mic the carrier signal amplitude strongly varies . isn”t fm circuit supposed to change frequency only
can you give me FM receiver circuit diagram and documentation.
Thank you so brother for this electronics knoledge website..from Algeria
HI.
I Have replaced the vc1 by a 13pf capacitor and it works perfectly!!!!!
cound find any variable capacitor over here . :o(