Have you ever wanted to broadcast your own radio station within your neighborhood? Ever get curious on where people get those "Surveillance Bugs" from spy and action movies? This small and simple FM transmitter is the toy that geeks have always wanted.

FM transmitters can be complicated to build, that's why I'm teaching you how to make a foolproof FM transmitter. There's no need to buy kits, this tutorial includes the PCB layout and the schematics. It has a range of up to 1/4 mile or more. It's great for room monitoring, baby listening and nature research.

My Experience:

FM transmitters remind me of my early years in electronics. When I was 8, I came across Art Swan's FM transmitter circuit. At the time I had no idea of where I'm supposed to buy the parts, so I recycled mine out of junk. I guess the biggest struggle that you're going to face is finding a trimmer capacitor. I'll give some tips on the last step of this instructable. In a nutshell, I highly recommend this project for everyone and also those who are still new in electronics.

>>>>>>>WARNING: You may experience nostalgia! :D<<<<<<<

Technical Specifications:

- 1/4 Mile Radius Range

-Powered By A 9V Battery

- Lasts For Several Days

- Adjustable 87-108MHz

Please Watch: Celebrating the 1st episode of my new YouTube channel! It's my first time to document a project with videography. I hope you guys enjoy the vid! Please leave a comment below, I would appreciate some advise regarding the video.

Disclaimer: This project is for educational purposes only and is not intended to air/ interfere with present radio channels. Neither site nor I, am liable for careless actions. Please check for the legality before attempting the project within your area. As long as

Step 1: Gather the Parts

All of these are available on any branch of RadioShack! :)



- Copper Clad PCB/ Perfboard

- Solid Gauge # 18 Wire

- Electret Microphone

- ¼" Bolt



- 2N3904 General NPN Transistor (2x)



- 15pF or 40pF Trimmer Capacitor

- 100nF Ceramic Capacitor (2x)

- 10nF Ceramic Capacitor

- 4pF Ceramic Capacitor



- 1M Ohm ¼w Resistor

- 100K Ohm ¼w Resistor

- 10K Ohm ¼w Resistor (3x)

- 1K Ohm ¼w Resistor

- 100 Ohm ¼w Resistor



- A Pair Of Pliers

- Soldering Iron

- Hot Glue Gun

Step 2: PCB & Schematics

I designed a compact PCB layout for Art Swan's miniature FM transmitter circuit using Fritzing. Use this step as your reference for the assembly.


About The Circuit: These is the exact description of Art Swan, the circuit's Author, "This miniature transmitter is easy to construct and can be picked up on any standard FM receiver. It has a range of up to 1/4 mile or more. It's great for room monitoring, baby listening and nature research"


Download Link:https://docs.google.com/file/d/0BwP5mrDBOvNYaHFnME...

Step 3: Print the PCB Layout

Download the PDF file then print it with your printer's standard setting then cut the printed layout. Be careful when cutting, the tip of my thumb got sliced by the sharp cutter blade.


Download Link: https://drive.google.com/file/d/0BwP5mrDBOvNYaHFn...

Step 4: Develop the PCB

I'm using something what's called presensitized PCB fabrication, it's different from the toner transfer method. If you're not familiar with presensitized PCBs, better go with the toner transfer method.


Presensitized PCBs: I expose mine directly to a 10W fluorescent lamp for 5:20 minutes then use a dilute solution of Sodium Hydroxide to develop the exposed PCB.

Here's a separate tutorial for the PCB fabrication:

Step 5: Etch the PCB

Pour Ferric Chloride on a plastic tray then start to etch the PCB.

Step 6: Clean the PCB

Use a swab and Acetone to remove the photo-positive layer/ toner.

Step 7: Solder the Components

Use step #2 as your reference. Solder the smaller parts first. Start with the resistors, the capacitors, the transistors, the coil, the antenna then the 9V cattery clip.

Step 8: Construct the Coil

Strip a solid gauge #18 wire. Use a 1/4" bolt then turn the wire 7-8 times.

Step 9: Adding the Antenna

Solder a hook-up wire to the antenna pin, it's located on the 2nd transistor's collector pin. Use a maximum of 8 inches an a minimum of 5 inches.

Step 10: Recycle a Battery Clip

The key to this compact transmitter is the ingenious battery clip.You can get one by dismantling an scrap 9v battery.

Step 11: Glue Them Together

Apply a generous blob of hot glue to hold the clip and the transmitter circuit together.

Step 12: Breadboard Version

Recently, people have been asking me if it's possible to make this project without having to fabricate a PCB. The answer is yes. In fact I built my first FM transmitter on a perfboard. I guess some are new to this, no worries I'm here to teach you.

The answer to this is a "Perfboard/ Prototype board. It's a PCB designed for prototyping circuits. There are three types of perfboards, the one that suits our needs is the dot matrix version. If you're new to this, make magazine has handy YouTube tutorial.

Step 13: Tune the Transmitter

Turn on your radio then tune it to your desired channel frequency. You'll get more range from the vacant channels. Don't touch the coil, just turn the trimmer capacitor until you hear a feedback from the radio.

Step 14: Q&A - Tips & Tricks

Where Can I Buy The Parts?

If you live in the US, all the parts that I've used are available from Radioshack. You don't believe me? The parts from my first non-recycled transmitter came from RadioShack, Long Island, NY branch.

Any Alternatives For The Trimmer Capacitor?

Most likely, you'll find one from a scrap transistor radios however you can replace it with a 20pF ceramic capacitor then rely on the coil's adjustment for compensation. Trimmer caps are color coded, only use the Red, Green or Yellow. I used the yellow since it covers a wider range.

Which Wire Should I Use?

Only use solid wires that has a thickness of 18 - 22 gauge. When I was still a novice hobbyist, I was worried about the strict selection of parts. Don't worry too much, eventually you'll learn to improvise when parts are not available.

Why Does The Frequency Change After Tuning?

Let's admit it, tuning the radio is a bloody challenge! If you use a metal screw driver to tune the trimmer cap, chances are you'll end up having a different frequency broadcast the moment you lift the screw driver. This is why non conductive screw drivers are recommended.

Where Can I Find A Non-Conductive Screwdriver?

You'll easily find one from a PC repair shop, or maybe form a hardware store. If you really can't find one, the famous Little Bits kit comes with it.

Is It Possible To Connect A 3.5mm Audio Jack?

Yes, it's possible! All you need to do is to link the common ground then solder a 1K ohm resistor each channel (L & R) forming a junction. Now solder a wire from the junction to U1's collector pin (refer to the schematic). You can now connect your MP3 player! I'll post an additional step regarding this mod.

Can I Hook This On A 12v Car Battery?

This project would still operate at voltages between 7v-14v, so yeah it's compatible. If you want to stay safe and prevent the circuit from burning, solder a 10 ohm resistor in series with the FM transmitter and 12v battery.

Is This Legal?

As long as you don't use it to spy on others and not use a long & huge antenna then yes, it's legal. Just don't use it near an airport. For more info, pleas read the FCC Rules.

Step 15: Don't Forget to Leave a Comment [Stay Tuned]

Please don't forget leave a comment below. Thank you!


2nd Week - DIY Pocket Spudgun

3rd Week - Homebrew Continuous Tazer

4th Week - Crystal Radio

5th Week - Solar Car (School Investigatory Project)

<p>I made it ..... but it only produces a continuous sine wave sound in the radio .</p><p>can anyone help me figure out its problem ?</p>
<p>What do you mean connect to the common ground and solder 2 1k resistors to form a junction?</p>
<p>Please dont remove this page till i make my own copy of this transmitter</p>
<p>hi whats the schematics of the pcb when use relly?????how can i use relle instead of the trimmer??? please answer</p>
<p>Fantastic. I was wondering if you were still planning on adding a step for the 3.5mm mini jack mod? Cheers! </p>
<p>can i use mobile's radio or it need actual FM radio.One more thing , I didn't get trimmer capacitor ,got a capacitor with three legs can it be used.</p><p>what are the specifications of the mic used. </p>
<p><em>PLEASE HELP ME!!</em></p><em><strong>HOW DO YOU MEASURE THE FRECUENCY WITH THE POLYMETRE???</strong></em>
hey! could u plz tell me the size of pcb layout?
Thanks dude. Works great.
hey! could u plz tell me the size of pcb layout?
hey! could u plz tell me the size of pcb layout?
Pcb layout size of print what?
Sorry, I'm not sure what your question is exactly.
+255715255490 <br>Whatssap me
<p>im already done make the circuit but im still cannot get the frequency that i want..can u look my circuit if have mistake..tq</p>
<p>I found that getting a specified frequency given the author's proposed hardware setup is quite difficult. I end up getting whatever frequency is not broadcasting very strongly in my area. Just try scanning through all AM and FM frequencies and turning up the gain on your transmitter.</p>
<p>How does one turn up the gain on this transmitter ?</p>
<p>Increase the power supply voltage would be the quick and dirtiest way. A few others might be to change R2 and R3 to increase the bias voltage at the base of that transistor. Or maybe decrease R4. There are a few others, but again, it comes down to increasing the collector current of the transistors which would happen by change the collector resistance, increasing the base voltage/current, or by increasing the power supply voltage.</p>
<p>its working or not</p>
<p>It worked fine. I couldn't specify a transmit frequency, but I could pick up the signal on a few open channels.</p>
Would u sent me a breadboard circuit degin photo?
May i change 1m ohm 1/4w with 1m ohm 1/2w resistor? And change 4pf ceramic capacitor with 5pf? :)
anybody help plzz
help plz. i want to know the pcb size
I connected the circuit as per circuit diagram but there is no any out put.what the input for the circuit and how much frequency range it is?
<p>I don't find 4pf ceramic capacitor </p>
<p>The schematic diagram included a 0.01pF Capacitor - which is not existent anywhere (unless probably its a DIY capacitor). This capacitor isn't included on the parts list so i guess its a mistake</p>
<p>Search for 10 nF</p>
<p>i couldnt find an 10nf capacitor in my area or the site buy components from</p>
<p>email me your address and I mail you a cpl</p>
<p>0.01pF is not equal to 10nF... i'm guessing that 10nf (equals 0.01 microFarad) is in place for the 0.01pF.... - its probably a typo error</p>
<p>Ye but 10nf works for sure so just get that one :P</p>
<p>what you can do is twist two pieces of plastic coated insulated wire to make up your own cap to that value of 0.01pf</p><p>any advice anyone can contact me the expert</p>
<p>Probably so. I didn't see it anywhere either.</p>
Problem is I couldn't find a trimmer capacitor like you said but I found one with three terminals and a transperant shell. And i made it and ran it but there was no clear signal from transmitter but an interfierence signal from transmitter to radio with high pich noise. Any help guys?
<p>ill trade you a cpl for a circuit board</p>
<p>ebay, you can get like 10 for $4</p>
<p>cant I make this without the circuit board? Solder the components in order or on a few little bare copper wires? What is a good mic? A mic that's more sensitive?</p>
<p>Is it possible to make a similar thing with longer range? At least a mile</p>
Maybe you could attach a fritzing. It would help me a lot. Definitely building this!!! AWESOME!!!
Hello... somebody help in getting my transmitter correct... actually im able to transmit but the problem is I have to hold it in certain position or even if I keep the transmitter in one place I have to move my body or wave my hand to a place where im able to hear whistle sound... sounds funny but this is the problem im facing...
<p>Can I use 3,9 pF capacitor and 2W resistors ?</p>
<p>you can adda the caps in series if you havnt got correct values or put them in parallel to get the caps in 20% of the value you need or you can alter the windings on the coil either way its not set in stone you are basically altering the magnetic fild of the coil so if you mess about with values and changing parts you will learn how it is working properly instead of just copying someone elses circuit</p>
<p>Thanks a lot dude :)</p>
I'm quite confused. In your video it says 20pf or 40pf trimmer cap, but in your written instructions 8t says 15pf or 40pf trimmer cap. Please kindly explain.. :)
<p>it doesn't matter that much as long as its in 20% ime and have been a television engineer if all the parts were 20% either way it would not matter</p>
<p>40pf for sure</p>
<p>I know it's a silly question and I think I already know the answer but still, please tell me. Does change in Inductance of a coil affect its range? If so, how are both related?</p>

About This Instructable




Bio: Hi I'm Angelo! I am a 18 y/o college sophomore taking my majors in BS-ECE at the DLSU. I use my course as ... More »
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