wireless audio Electronics

FM Transmitter – Beginners Guide – Its so easy!


How it’s so easy to start making FM transmitters?

So you want to make an FM transmitter for your project? Or maybe you just want to try your hands on wireless voice transmission? Whatever might be the reason for making your first FM transmitter, you are at the right place to get started and spread your voice in the air though electromagnetic waves.

Though there are a lot of guides out there in the internet, but as per my experience none of the guides cover all the important information. There are even some websites stating that making an FM transmitter is very complicated and you kind of need good luck with your pcb and components to get success. This is completely false, when you are just getting started or not making a military grade ambitious project including encrypted wireless communication. Whoh!

Well much of talking ….

Lets get started….

Well I must say that it’s the best choice that you are starting with an FM transmitter rather than AM or shortwave. FM transmitters are the easiest and the result which you get is really rewarding. FM transmitters can pick up very faint sound, are crystal clear, small and simple.

Important tip:- Just subscribe to this blog Positive Manash so that you can follow-up my posts and guides without missing.

Step 1

Get yourself these components:-

Simple FM transmitter component list:-

1) Electret Microphone

2) 10 nF capacitor

3) 200 ohms resistor

4) 4.7 Kohm resistor

5) 6.8 pF capacitor

6) 2N2222 or 2N3904 or PN2222A trasistor

7) 36pF or 33pF capacitors

8) 2 – 22pF Trim Cap

9) Inductor coil with 5 turns and .5 cm dia. (Insulated copper coil)

10) 10 inch antenna wire. (any single stranded wire)

11) 3V DC supply (AA, AAA or coin cell battery)

 

Step 2

The following is the circuit diagram. Make the circuit first on breadboard then on copper clad. I recommend you to make it on copper clad of high quality for your final design as the performance of this FM transmitter increases.

FM transmitter Circuit

Basic FM transmitter Circuit

Just Give a try. We will help

 

 

Step 3

Tuning the FM transmitter

Turn the variable capacitor or the air trimmer (whatever you say :-) ) to the position where its capacitance will be 2pF. Then take a radio in which you want to hear your transmitted signal for the time being and keep it at 96 MHz or near to it at a blank spot without any existing broadcast. Then slowly compress or stretch the length of the inductor coil to adjust the FM transmitter’s broadcasting frequency. Once you get near to it. Fine tune further by adjusting the air trimmer of your FM transmitter with some plastic substance. (Metals will give you wrong tuning).

 

If everything is fine, you will be able to properly tune your fm transmitter. But if you find any problem then you would need to check things.

 

If you need any help in building this fm transmitter then you can comment on this post.

 

Facts related to this FM transmitter:

1. It is a single transistor FM transmitter.

2. It can transmit to a distance of 30m inside a building with 4 RCC walls in between.

3. In open it can transmit to around 80-100 meters.

4. It is very sensitive and can even pick up the sound of a pin drop.

5. It can be used as a bug.

6. It can’t be handheld. Subscribe to get informed about the handheld version of FM transmitter that I will post soon.

7. Frequency may drift if you touch it.

Buy GY560 frequency counter used for measuring frequency at the cheapest prize at click here . I assure you to have genuine product from this site.

 

See it working at

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Subscribe to my blog immediately so that you don’t miss anything. I will be posting the working of this simple fm transmitter’s circuit. Then would introduce you to a better and more stable version of fm transmitter. I would also show you how you can avoid the complicated inductor coil and use another readymade component instead.

Stats

Ease of Use 81%
Stability 58%
Learning Scope 93%
Final Thoughts

Overall Score 77%
Readers Rating
4 votes
84

8 comments
Khaledaziz33
Khaledaziz33

what is the thickness of the coil wire 

nikhil
nikhil

how do I connect the 3 pin capacitor

RAHUL DWIVEDI
RAHUL DWIVEDI

can u mail pcb layout for this.......evolutionstorms@gmail.com


ManashRaja
ManashRaja moderator

@Khaledaziz33 The thickness is about 5mm diameter. It was written in the part list above. So hows your project going on?

ManashRaja
ManashRaja moderator

@nikhil See the three pin capacitor has two pins on its extreme ends (along the diameter of the circular cross section) and one between them. The one between them is called sweep pin. So capacitance varies between the sweep pin and any one of the terminal pin. So you need to connect any one of the terminal and the sweep pin in your circuit as you would connect a two pin capacitor.

ManashRaja
ManashRaja moderator

@RAHUL DWIVEDI I don't happen to have the pcb files now. But you can easily build this circuit and pcb on Eagle Cad as it has such a few components. Even though, I will search and send you if I get as I have your email address.