Introduction: Simple Surveillence Bug

Picture of Simple Surveillence Bug

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Hello every one, in this instructable i will show you how to build a simple surveillence bug, other wise known as an Fm transmiter. its an extremly fun and entertaining project that you can do at home while learning about an essential tecnollogy that has become more and more frequent throughout the years.

i would like to appologise to all my viewers and followers for not posting any thing lately, I've been so busy that I haven't been able build any thing, so I'm hopeing that this will make up for that.

If you are new to electronics I will make this as simple as possible telling what every component does and is for and exactly where it goes. However that dosent mean that it will be easy, you will need some basic soldering skills as well as some knowledge on basic components.

I hope you like this instructable, be sure to subscribe to me for many more instructables like this one coming soon, also if you like this then be sure to favorite it. If you have any questions or comments then be sure to leave them below, I'm very good at responding and if I don't right away then just be patient and I will respond to you soon. Please be sure to vote for me, thank you.

Step 1:

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Here what you will need:

  1. An NPN 2n3904 transistor
  2. A 9volt battery clip
  3. Copper clad board
  4. (2x) 100 pf ceramic disc capacitor
  5. (2x) 0.01 uf ceramic disc capacitor
  6. A small micro phone
  7. Covered wire
  8. Un covered copper wire 18 gauge
  9. 10 uf capacitor
  10. And the following resistors- 470 ohm, 10k ohm, and 22 k ohm


  1. soldering iron
  2. 60/40 rosin core solder
  3. Pliers
  4. Wire cutters
  5. Fm radio recover

All these items can be purchased at your local radio shack or online.

    Step 2:

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    In the first picture I have given you guys a scamatic to follow but it isn't needed to make this because I will be very descriptive.

    Start by cutting your copper clad board. Cut out a ground plane that is 1.5 inches by 1 inch, then cut back rail along with the 4 other small pieces. In the picture I have marked each piece with a number. 1 is the back rail, 2 is 2, 3 is 3, 4 is 4, 5 is 5, and G is ground. I will tell you where to solder each component.

    Step 3:

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    glue the pieces on as shone and let it dry.

    Step 4:

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    I didn't take any pictures of the coil being made and I apologize for that, but all you need to do is wrap the 18 guage copper wire around a bolt several times, then you unscrew it from the bolt like interviewing a nut from a bolt. Then you will make small feet by bending the wire ends in the same direction. Once you have your coil made you will solder it to plate 1and 5 as seen in the picture.

    Step 5:

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    now take a 0.01 uf ceramic disc capacitor and solder one wire to plate 5 and the other to ground as shone In the picture above.

    Step 6:

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    next solder the 22 k ohm risistor to the plates 4 and 5 and cut off the extra wire so it's not in the way. Here's a tip if your having trouble with the soldering, pre tin or pre solder the connections. This will allow the two pieces to bond together better.

    Step 7:

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    now you will need to add the 10 uF capacitor to the circuit. First look at your cap. It should have two wires, one of these wires will have a big white stripe pointing at it this is the negative wire and will be solders to plate 3. The other wire will be soldered to plate 4.

    Step 8:

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    now for another resistor, the 10 k ohm to be exact. One end will go to ground and the other end will go on plate 4 as shone In the picture.

    Step 9:

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    now we will add the other 0.01 uF ceramic disc capacitor. One wire will go on plate 4 and the other will go to ground, I found a nice little place on the edge of the ground plate for this.

    Step 10:

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    now for the hard part adding the transistor, assuming that you made it this far tells me that your over qualified for this, however one little mistake will make it not work so pay close attention to these two steps where I explained how to add the transistor.

    Start by soldering the the emitter or pin 1 to plate 2.

    Step 11:

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    Next solder the base or pin 2 to plate 4, and solder the collector or pin 3 to plate 1.

    Step 12:

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    next solder the 100 pF ceramic disc capacitor to 1 and 2

    Step 13:

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    now we can add the final resistor, yayyyyy. Solder one end to plate 2 and solder the other end to ground.

    Step 14:

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    next you will add the final capacitor. Take the other 100 pF ceramic disc capacitor and solder one wire to plate 1 and the other to ground.

    Step 15:

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    here we will be adding the 9 volt battery connecter to the circuit. Solder the red wire or positive lead to plate 5. Solder the black wire or negative lead to ground.

    DO NOT hook the battery up yet we are still not quite done, doing this could damage the circuit.

    Step 16:

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    now you will add one of the most important parts, the microphone. Start by soldering the lighter colored wire to plate 3, then solder the darker colored wire to ground.

    Step 17:

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    finally cut a foot long piece of rubber coated wire and solder it to plate 1, this is your antenna.

    Step 18:

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    when your done it should look like this. To use it plug in the battery, get an fm radio and make a recognizable sound next to the transmitter. Search through the different channels until you find the sound, this is the frequency that your transmitter gives out. Now your ready to spy on anyone. Be sure to keep in mind though that it is illegal in some states or countries to use an Fm transmitter without a permit, be sure to check local laws in your are.


    bmostert (author)2015-11-12

    When calculating the dimensions of the inductor do you use the capacitance of the whole circuit or just one capacitor?

    I'm using this site

    and this site

    to find the length, diameter, and turns my inductor must be. The only thing is I don't know how to calculate the capacitance. Thanks for the help!

    bmostert (author)2015-11-09

    Quite new to electronics. I scavenged some capacitors from an old stompbox, but they're not ceramic disk ones, and not nearly as big looking as the ones you have. They are the right values though. Mine are the ones in the picture, I included the battery for scale. Thanks so much!

    Pure Carbon (author)bmostert2015-11-09

    All those will be fine for this project.

    logan.byrne.77 (author)2015-05-05

    I have a mess load of 27 Ohm resistors, would they work as well? I
    built one of these from Radio Shack in the 90's still have it the
    project but want to make one that can fit in a tricorder toy, for my

    Unfortunately I believe the resistors have to be at least close the ones I used, however I'm no expert, so you could try it and let me know your result.

    IronPatriot911 (author)2014-12-28

    what's the range on it?

    About 50 feet.

    dRac24 (author)2014-10-28

    Need help..!!
    The microphones available here do not have wires with them...!! What to do...?? Please help..!!

    Pure Carbon (author)dRac242014-10-28

    If I had to assume, you just need to solder wires to it on the positive and negative terminals. I'm sure that you've tried that though, if you could post a picture then I would be able to better assess the problem. Until then there's nothing more I can do, sorry :( .

    manuka (author)2014-09-17

    Classic 88-108MHz FM bugs like this are fun to make, BUT they're both weak & very unstable. They'll hence usually be swamped (due to the FM capture effect) in urban regions by powerful broadcasters. Today's crowded FM band makes them near impossible to find & keep tuned on a FM receiver!

    For serious work it's probably now better use a superior circuit, hack a car digital readout MP3 transmitter or use a UHF CB transceiver (switched to VOX) set to a precise "quiet" frequency.

    ALERT: Ensure "spying" legalities are observed or you may get your nose punched in - at the very least ...

    Stan. - ZL2APS since 1967

    Pure Carbon (author)manuka2014-09-21

    I completely agree, these small things are hard to find the frequency for. A more complex circuit will work wonderfully and are more ment for the pros. This simple circuit is more ment for educating people about how radio works. Thank you for your comment and please be sure to vote for me.

    jupton2 (author)2014-09-05

    just one other thing, what frequency (roughly) does it emit? will you be able to pick it up on a normal FM radio receiver?

    GreeceFallout (author)jupton22014-09-16

    well he presents it as an fm transmitter so you should be able to pick within the fm band

    nossvagyok (author)2014-09-13

    very nice :)

    Pure Carbon (author)nossvagyok2014-09-15


    Silent_Shadow (author)2014-09-08

    Where could I get the parts?

    Radioshack, or online. Don't forget to vote

    sosyalist (author)2014-09-08

    testing video ?

    Pure Carbon (author)sosyalist2014-09-09

    I might put one up in the future.

    throbscottle (author)2014-09-08

    This is a very similar circuit to one I built as a teen, in the '80's. I fitted mine into an empty wristwatch case, it had the insert from a magnetic earpiece to act as a microphone (gave better results than an electret). I cut the leads off the resistors and soldered direct to their end-caps (no smd in those days) and point to point wired all the components, no pcb because it took up too much space. I just made a circle out of a bit of tin can, to fit inside the case, and mounted all the components in that. It was an AM transmitter though, operating on the FM band. Filled up the space with wax to stop vibration. You could just about pick up the signal with an FM receiver, lots of distortion because it was an AM not FM signal.

    The fatal flaws in my design were, you needed an antenna wire going up your arm, and it needed a pp3 battery to run, like yours, so that had to be concealed somewhere too!

    I never did build an AM on FM band receiver for it.

    neaton1 (author)throbscottle2014-09-08

    Nice... Any idea on how to set the specific bandwidth and frequency, though?

    throbscottle (author)neaton12014-09-08

    I did mine by adjusting the coil. Same thing would work with the bug shown here. You would need a frequency meter or oscilloscope to set the frequency accurately, or just tune it so it matches what you want on the receiver.

    neaton1 (author)throbscottle2014-09-08

    Thanks, all that's left is to build a few of these to help end a neighbor's actions. Hopefully I can get 3 of them tuned close enough to each other so I can record all 3 at once...

    throbscottle (author)2014-09-08

    Great instructable, really quite a fascinating little circuit, and I love the method of construction, but I have a question. How does the modulation work? I'm guessing the transistor's base/collector junction is acting as a varicap, is it?????

    tmaragakis (author)2014-09-08

    Great instructable, but why FM and not AM? It's easier for someone to tune in and listen by mistake, on their radio with FM.

    dRac24 (author)2014-09-07

    I liked it, I voted it, cool instructable bro...

    Pure Carbon (author)dRac242014-09-07

    thank you so much.

    imperio (author)2014-09-07


    è la prima volta che vedo questo sistema per realizzare un circuito stampato a due strati! Congratulazioni!


    Pure Carbon (author)imperio2014-09-07

    Grazie. : )

    Raphango (author)2014-09-07

    Congrats man! ^^,

    Veru nice project! =D

    Pure Carbon (author)Raphango2014-09-07

    thank you very much. Hope you don't mind voting for me.

    dezduino (author)2014-09-07

    My Dad made these when was a kid back in the 60's. My Parents would encourage me to have friends spend the nite then spy on us. He would use a wire with a safety pin on it as the antennae Then hang it on the back of a curtain. It apparently worked very well.

    Pure Carbon (author)dezduino2014-09-07

    you know parents, always need to know what's going.

    espdp2 (author)dezduino2014-09-07

    And you grew up thinking your parents were psychic! :-)

    kag432 (author)2014-09-07

    Sorry I am still new to FM, but is there a reason you didn't just buy an inductor with the desired inductance (instead of making your own coil)?

    Pure Carbon (author)kag4322014-09-07

    no need to apologize. You need to make your own because inducers have the wire wrapped around itself, where a coil is not and is of equal spacing between the wires. Hope I could answer your question, and be sure to vote for me.

    64Anthonyp (author)2014-09-06

    Used something similar to this many years ago. It was a kit that fit inside a Tic Tac box and used an AA battery. Used for surveillance when houses had a car park out of sight so we knew when the target was leaving home. (I was a licensed Inquiry Agent.)

    Pure Carbon (author)64Anthonyp2014-09-06

    that's so cool, thanks for your comment. I'm not sure what a licenced inquiry agent is, but it sounds awesome. Do you think I could get your vote? : )

    rpotts2 (author)Pure Carbon2014-09-07

    Probably a UK private investigator or something similar.

    you know those Brits and their "proper" english...

    JK, +64anthonyp. ;^)

    Pure Carbon (author)rpotts22014-09-07

    hahaha, yes.

    rpotts2 (author)2014-09-07

    favorite-ing for my Maker group.

    Pure Carbon (author)rpotts22014-09-07

    sweet, thank you for your support

    ezhilabhi (author)2014-09-06

    Cool instructable man.You know there is a similar youtube video by dazaro3.But this looks smaller than that.Keep it up :)

    ezhilabhi (author)ezhilabhi2014-09-06

    I voted

    Pure Carbon (author)ezhilabhi2014-09-06

    that video sounds interesting I will have to watch it later today. Thanks for voting for me I really appreciate I.

    jupton2 (author)2014-09-05

    what frequency does it kick out? gonna have a shot at making it

    ezhilabhi (author)jupton22014-09-06

    The frequency depends on the length between the coil made using the uncovered copper wire.The longer the length the more the frequency.

    Pure Carbon (author)jupton22014-09-05

    I'm so sorry about taking so long to respond. Mine was about a 97 MHz, but if I had to give a range it would be between 95 MHz to 100 MHz. Hopefully I can get your vote, right.

    jupton2 (author)2014-09-05

    I tried to vote twice... and thanks! :D can't wait to try this. I'm going for a run to the electronics store after work tomorrow

    Pure Carbon (author)jupton22014-09-05

    sweet, I can't thank you enough.

    About This Instructable




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