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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! :)

______________________________

MISC:

- Copper Clad PCB/ Perfboard

- Solid Gauge # 18 Wire

- Electret Microphone

- ¼" Bolt

______________________________

Transistors:

- 2N3904 General NPN Transistor (2x)

______________________________

Capacitors:

- 15pF or 40pF Trimmer Capacitor

- 100nF Ceramic Capacitor (2x)

- 10nF Ceramic Capacitor

- 4pF Ceramic Capacitor

______________________________

Resistors:

- 1M Ohm ¼w Resistor

- 100K Ohm ¼w Resistor

- 10K Ohm ¼w Resistor (3x)

- 1K Ohm ¼w Resistor

- 100 Ohm ¼w Resistor

______________________________

Tools:

- A Pair Of Pliers

- Soldering Iron

- Hot Glue Gun

<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>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>Probably so. I didn't see it anywhere either.</p>
I'm facing the problem while transmission . The signal is jumping eventually
<p>Works fine but I got 1 Problem: The Microphone is really silent...i got to turn my mobile on full volume to get decent volume in the radio...is there a way to amplify the mic more?</p>
Thanks dude. Works great.
<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>
<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>
Would u sent me a breadboard circuit degin photo?
Pcb layout size of print what?
Sorry, I'm not sure what your question is exactly.
<p>how if i use the value trimmer capacitor 120pF..can or not?</p>
<p>Hi, i tried to make it with exact component but still not getting any output. Any help?</p>
<p>can i operate it at 5 volts? I want to revise it design and make it run with USB power.</p>
<p>If you remove the resistors in the correct places and place a wire there instead, you might be able to run it on a lower voltage.</p>
<p>where does the middle pin of the capacitor go?</p>
I think that it should go in the transistor<br>
I am not able to get 4pf ceramic capacitor. Can i replace it with any other component?
<p>I was just wondering how would you increase the range of this?</p>
<p>its probably the antenna. if you want a very long range but in one direction make a yagi. if you want just more better range in all directions (not as good for range as a yagi but better then a piece of wire) make a dipole. you could also make a rf amp but the battery life would suffer and it would be bigger (also you would need to modify the PCB design)</p>
<p>This transmitter is literally impossible to tune without a non-conductive screwdriver. It really should be a part of the list of required tools!</p>
hello friend i have a confusion in assembling the 3.5mm audio jack in place of mic can u please explain or send a pic to me
<p>I would think that you could just do the trade 'straight across'. The positive would go to the positive, negative to negative. Or did you try that and get no result?</p>
<p>SomeTImes i get the output and sometimes Wont. <br>What Could be the problem . Any solution to this .<br>Any One Can Help me out with This ?</p>
I tried making this the other day and something went horribly wrong. I tried following both your actual photos and schematic, but still ended up with about three components out of place. do you think you could share a color coded drawing of the board with what components go into which holes? Because I think the problem I'm having is that I opted to use a pre-drilled prototyping board rather than etch one for the first run. So now I've got to de-solder all my components and try again.
Hi, I am looking to make a radio transmitter for a larger project for school and I was wondering if it was possible to play a sound pattern continually, for example a beep?<br><br>Thanks
Amazing instructable! I remember reading about these bugs in one of the eveil genius books and they were small enough to fit in a soda cap running off of a 3V button cell battery. Is there any way to adapt this circuit to also work on 3V instead of 9V? Shrinking it down is what interests me as im planing on using 0603 SMD components for it.
<p>Yes! Very easily, just attach 3 of the 3V button cells in series, like so:</p><p>+V1- +V2- +V3-</p><p>The positive face of V1 becomes the positive face of the battery while the negative face of V3 becomes the negative face of the battery. A decent way to attach the batteries might be to just press them together firmly and hot glue the seam, but not the faces. That way the faces can continue the circuit while the highly resistive glue holds the faces together. This would have the added bonus of tripling the battery life of the transmitter.</p>
Can copper 22 # gauge wire be used instead?
<p>yes . you can</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.. :)
Can i use any capacitor without using 4pF ceramic capacitor?? Pls answer.
<p>i was woundering how would you change the frequency to be able to use more than one in a small space ?</p>
How to find the capacitance of trimmer capacitor and how to find the certine frequency?
<p>is it possible to connect a LASER as the input to the transmitter and then decode the signal at the receiver so as to make a wireless counter?</p>
<p>yeah posible</p><p>but u need modulated signal </p>
<p>how can i know in which freqency the transmitter transmitting</p>
<p>it doesnt work ,, may be problem with inductance</p>
Can i use 1/2 watt resistors instead of 1/4?
Yes. You can use even 1/8 watt resistors ;)
<p>Hello,</p><p>Could I use a 2n2222 instead of the 2N3904?</p><p>Thanks</p>
<p>probably. if you do try it could you let me know how it turns our as i don&quot;t have any 3904s either</p>
<p>any body tell me </p><p>how can i set the frequency on our fm radio</p>
<p>Adjust your 15pF or 40pF Trimmer Capacitor</p>
<p>go through the video first <br>at the last you can see that he(the tech guy) adjusts the screw on the top to get get the desired frequency<br>first you need to set the frequency through you wanna hear in the receiver<br>then adjust the screw until you can hear clearly<br></p><p>let me know if it works </p>

About This Instructable

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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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