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 went to RadioShack but I could not find a trimmer capacitor.Any tips? </p>
<p>I built this using smd parts but can't get a crystal clear signal.<br>The radio picks up the signal but it's very garbled and noisy.<br>Going to try a different inductor and antenna length and will report back.</p>
<p>nice idea!! what package have you used? found a trimmer capacitor smd</p>
<p>Hey, your instructable is great. Came across it on youtube. I don't have stuff to etch a PCB so I made the bug on a Pref board. But it is not working. I tried to go through each frequency and also used the trimmer capacitor, but no results. I had made mistakes in the circuit twice and now its third time and everything connections wise looks fine. I know my work is sloppy, please excuse that.</p>
Hey, just a tip, solder the components closely to each other. Someone told me that the closer the components are, esp the inductor, the more chances it will work. :)
I built it in a breadboard but it is not working I can't get signal to my mobile gm radio software <br>I'm attaching the photograph of the circuit<br>please check whether I'm doing anything wrong
<p>i made it but its not working... i think maybe the transistors are placed the wrong way.. as in your pictures they are facing the inductor coil. plz help me... Thanks ;(</p>
<p>i think you printed or faced your layout in a wrong way</p>
<p>in case i cant use copper</p><p>will this be okey?</p><p>http://www.aliexpress.com/item/1mm-black-plated-aluminum-jewelry-craft-wire-coil-10m-roll-10m-2-soft-DIY-anodized-aluminium/32218673288.html?spm=2114.01020208.3.13.0wXV9R&amp;ws_ab_test=searchweb201556_2_79_78_77_80,searchweb201644_5,searchweb201560_9</p>
<p>please could i use copper to make the coil</p>
<p>Hiii. I'm a internal student of university of Kelaniya Sri Lanka. I want to use this cct as a part of our final year project. We are designing a digital stethoscope. We want to transmit an analog signal (heart pulse signal) to a few distance. Can i use this fm transmitter for that purpose. Please reply me... I made your cct today. Now we are going to test this.. Anyway thank you very much your work...</p>
<p>Hi. I have build it but it is not working. I use 4.7PF instead of 4PF and 22PF trimmer capacitor.</p>
<p>instead of cutting out a 9v battery its better to use a 9v battery holder </p>
<p>NICE ONE !!!!!!!!!</p>
I absolutely love this project! I love it so much that I've decided to make it for my capstone. I just went to RadioShack earlier and was able to find everything except for the 4pF ceramic capacitor. I noticed, in your list of materials, it says to use a 4pF, but in the schematic, it says 4.7pF. which is it? 4 or 4.7?? and also, my teacher suggested that I use a trimmer to trim down the capacitance to where I need it to be. is that a good alternative if I'm unable to find the 4 or 4.7pF? please respond ASAP because I have a deadline for this project. Thanks!
<p>Sir may I use a 60pF trimmer capacitor?</p>
<p>can we listen to these frequescies using mobile phone?</p>
<p>can i also use copper cabels from an old transformer and an 20pf trimmer capacitor ?</p>
<p>so say i want to make it a personal radio station just for fun (yes i know i could just build a better, more powerful curcuit) can i extend my entenna over 8 in. would that help the range</p>
<p>once you know the frequency it transmits on you can create a resonant antenna using, for example, a &quot;dipole calculator&quot; (google it), to know the exact length to cut the antenna..</p><p>you should also be able to add the same length of wire to the ground to work as the &quot;couterpoise&quot; (the second half of the dipole)</p><p>this type of thing will probably significantly extend the range, and iirc the law that covers low power transmitters was changed to measured power at a specific range (rather than output power total) .. in other words, use this info at your own risk.. those fines will be STEEP</p>
<p>Hi, can I replace the 2N3904 General NPN Transistor by a BC547B? ThankYou!</p>
thank you
<p>hi can i replace the mic with a crystal or variable crystal to send a frequency signal to the receiver instead of fm signal from mic to the receiver</p><p>thanks </p>
<p>can i use 2n2222 transistor?</p>
<p>Very nice and excellent project </p>
<p> I made it! this my fm transmitter</p>
<p>thank for video ASCAS!</p>
<p>Nice little weekend project. I used an 0.1&mu;H axial inductor to achieve the correct frequency (clocked at 103.9 MHz, but it bounces around ALOT when your hands come close to the circuit). The signal is very faint and poor and crackly on the receiving radio, any way to clear up the signal? Would also like to stabilise the transmission frequency (stop it bouncing around when I adjust the trimming capacitor). Any thoughts?</p>
Hi ASCAS.<br>Im very impress by your work. Can you pleae send me a email. I have a job for you .<br>Lariosdesigns@gmail.com <br><br>Jonathan larios <br>Thank you
<p>Hey very nice tutorial.</p><p>And if you are still reading the comments.</p><p>I made the circuit on a bread board. But I am having problems in making the inductor coil. Kindly give me some advice.</p><p>I am attaching some pics.</p><p>Thanks in advance.</p>
Kenapa saya tidak bisa mendownload pdf nya?
http://www.evselectro.com/capacitors/trimmer-capacitors/trimmer-capacitor-blue-trimmer-1425 can you tell me please which one to use
Can you tell me which one to use http://www.evselectro.com/capacitors/trimmer-capacitors/trimmer-capacitor-blue-trimmer-1425
<p>Can you post the extra step to Connect A 3.5mm Audio Jack. I tried the method but maybe I was doing some mistake. :D</p>
<p>Can I mod it for frequency band 118 - 136 MHz (Aeronautical Com band)</p>
As a pilot I can't imagine what use it would be on aeronautical freq.? Probably illegal? Interfering with these bands could be disastrous.
As a Pilot, it is recommended that one may carry an additional handheld radio to facilitate comm in case of a radio failure. Those handhelds off the shelf are sometimes way too expensive. <br><br>Disastrous nature depends on the nature of the user. Many transceivers are sold online and at pilot shops, and can be easily bought for 300 to 500 dollars, or maybe less for the refurbished ones. <br><br>Now, how about a receiver on the said band (not a transmitter). Any tips? :)
another major problem, is that most aero frequencies are AM, this is an FM unit<br>
<p>Nautical frequencies are AM, But Aeronautical frequencies are both in AM and FM. Long Range communication is done over AM bands, like in the trans-oceanic flights. Near range or Short range is done on FM bands, because of, almost no static interference and stereophonic sound.</p><p>FM is 30 MHz to 300 MHz. Aero frequencies operate from 107 to 137 MHz. So its pretty much in the range. </p><p>Refer: </p><p>Common uses for VHF are FM radio broadcasting, television broadcasting, two way land mobile radio systems (emergency, business, private use and military), long range data communication up to several tens of kilometres with radio modems, amateur, and marine communications. <a href="https://en.wikipedia.org/wiki/Air_traffic_control" rel="nofollow"><font color="#0066cc">Air traffic control</font></a> communications and air navigation systems (e.g. <a href="https://en.wikipedia.org/wiki/VHF_omnidirectional_range" rel="nofollow"><font color="#0066cc">VOR</font></a>, <a href="https://en.wikipedia.org/wiki/Distance_measuring_equipment" rel="nofollow"><font color="#0066cc">DME</font></a> &amp; <a href="https://en.wikipedia.org/wiki/Instrument_landing_system" rel="nofollow"><font color="#0066cc">ILS</font></a>) work at distances of 100 kilometres or more to aircraft at cruising altitude.</p><p>Source Wikipedia: https://en.wikipedia.org/wiki/Very_high_frequency</p>
<p>can the antena/wire copper?</p>
i made it ;)
i made it :)
Instead of using a 4pf can I use a 5pf because that's the only one I can find and also instead of using a 40pf trimmer capacitor can I use a 50pf trimmer capacitor
<p>Hi, can I replace the 2N3904 General NPN Transistor by a BC547B? ThankYou!</p>
<p>Sir, Im in the Philippines and I am only a student.. Please help me..</p><p> I can use 100pf trimmer capacitor for 30pf capacitor... Because no available component in my city.. I recycle the 100pf trimmer capacitor for my old radio....<br>Thank.. You.. sir</p>
<p>Put a 47pF capacitor in series with the 100pF trimmer.</p>
<p>ahhh.. Thank you sir... :) : ) :)</p>
<p>Use a cheap RTL-SDR to check the frequency as you tune this.</p>
<p>This is what I designed for the students of my technical school, 21 years ago. It's a dc-coupled FM-transmitter with only one transistor, an electret-mic and a LED in it. I also designed a PCB for it. The range is about 200 meters (depending on several things). It has been build about 400 times and it always works. Wish you succes to build one for yourself !</p>

About This Instructable


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Bio: Join me as I build fun and random weekend projects!
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