Making a Simple Spybug.




About: I am a 35 yr. old licensed Iron worker/ Fabricator/ Welder/ Millwright but now in college currently in 2nd of 3rd year for Civil Engineering. I am a hacker & modder of all things and I love to fish, hunt, pl...

Here a easy instructable to make an FM spybug from a few common components. The hardest part in this is the making of the PCB. You can just use perf-board though if you perfer. Let's get started!

Step 1: Parts List

The following componenets are needed:

1) 1pc. 2N 3904 Transistor
2) 1pc. 4k7 Resistor (yellow, purple, red)
2) 1pc. 330 ohm Resistor (orange, orange, brown)
4)1pc. 4p7 Capacitor (4.7)
5) 1pc. 1n Capacitor (102)
6) 1pc. 22n Capacitor(223)
7) 1pc. 10-40p Trimmer Capacitor (green)
8) 1pc. 8 turn 6mm dia. wire (0.5)
9) 1pc. PCB or perf board, 9v Battery & connector, Antenna wire (14 in.)

Step 2: Diagram

Here's the PCB layout you will need if you are etching your own pcb. This is the route I took. This is very small (25mm by 20 mm) Later you will see why I made it this small.

Step 3: Trimmer Cap & Transistor

First I instal the Variable capacitor and the 2N 3904 transistor.

Step 4: Capacitors

Next we install the 4.7 & 1 n Capacitors in their places.

Step 5: Resistors

Next install the 4k7 and the 330 ohm resistors in place.

Step 6: Capacitor and Coil

Next we install the 22n capacitor then the 8 turn coill. Be sure to scrape the enamel off where you intend to solder or you will find the coil will not sit properly therefore leading to bad reception later when tuning.

Step 7: Battery Clip & Antenna

Next we will install the battery clip for the 9v that we will use to run the transmitter. I later choose to turn it and glue it to the bottom of the pcb so it is fastend to something and then the spybug will stand on end with the battery. After you solder the battery clip solder the antenna wire in. This will be the last to go on. You will have one last hole if you chose to make the pcb right next to the emmiter on the transistor, this is where the antenna wire will go.

Step 8: Tuning in to Radio.

After the spybug is all completed check all solder conections to m,ake sure it is in order. Remember it does not matter which way the capacitors or resistors face in this project. Tune your radio around 88 mhz-92 mhz. If you do not hear it right away tune the trimmer cap slightly until you hear a popping sound. Tap the electret microphone to see if thats the spot, from then on you should not have to ever trim the capacitor again. I chose to cover mine in shrink tubing, looks nice and I just had to cut a small access hole so I can still tune the trimmer cap, another small hole for the antenna. It was made this small so it can be glued to the top of the battery connector and sit ontop the 9v battery.



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    64 Discussions


    2 years ago

    please guys answer those questions.. i need to know and learn ( i'am new )

    -what trimmer capacity exactly? how can i take it off of machines to use it...
    - how the resistor function there? can i use a stronger resistor without causing problems to the other devices
    - 1pc. 1n Capacitor (102) what 1n (102) mean?

    -what is the difference between capacitor 5 and 6 and 2 ... does they work the same? how?
    - where do i put the battery
    - 1pc. 330 ohm Resisto why did he chose 330oh ? by what can i replace it ? can i creat something instead of using it?


    3 years ago

    Hi, I not sure turn of Coil in schematic its show 8T but your pic i see 11T ,What turn should i use?


    6 years ago on Introduction

    what can i use insted 10-40p Trimmer Capacitor?

    capacitor 001/AEC,22/AEC,18/AEC .can any one tell me the values of these capacitors....?plz

    lug big lug

    7 years ago on Introduction

    Do you think that you could post another pic of the PCB layout? The glare blanks out part of it, and i dont want to mess this up.


    8 years ago on Introduction

    2 questions: 1: will a regular microphone work? (like ones from telephone recievers) 2: can iuse a variable resistor? if not, where can i get a variable capacitor without going online? in step 7 you forgot to remove "title this step" overall, great instructable!

    5 replies

    Reply 8 years ago on Introduction

    To answer your questions Zack247; 1) YES! Telephone mic's work the best. They're small and work excellent. What you want is a 10mm Electret mic's they're called, small, round and silver in colour. 2) I think I found a trimmer capacitor in an old radio I tore apart, can't remember but I had to order a few from ebay for other projects I do. Maybey inside a telephone there might be one if you deside to tear that apart for your spybug. as for the variable resistor, Yes probley. Solder it all together and try it out and if it doesn't work then you know you need the trimmer cap. Good luck!


    Reply 7 years ago on Introduction

    a spybug is pretty much like a little radio transmitter, so you can hear stuff going on in another room without having to be there.


    Reply 7 years ago on Introduction

    Hi. You might want to add the microphone to the parts list. ;-)

    I also can not tell, where to solder the third leg of the variable capacitor. Since there is no clear photo of the capacitor soldered and looking at the schematics I also could not tell (I tried to redraw according to your schematics in Fritzing already). Can you (or anybody) help me out?

    Could you also post the pcb layout in a standard file format?

    I am a total newbie so please dont hurt me (too much) with your answer.



    Reply 8 years ago on Introduction

    Ok all the trimmer cap is for is to fine tune the spybug into the radio. Just tune your radio in around 88-94 mhz and slowly turn the trimmer cap clockwise until you hear a "pop" on the radio, then you have found the station that the spy bug will be in tune with. Tap the mic and talk into it until you hear your voice.


    Reply 8 years ago on Introduction

    ok first test out your bug and make sure your radio picks up some kind of interference. I also would recommend that if you are having problems tuning it then try a small portable radio, I found they work better than the big stereo systems. Set the band on nradio to 88-93 mHz and use a small NON- Conductive tuning tool to turn the trimmer cap. Turn very slowly and be patient it will take a few mins but once you find it you should never have to tune it again unless you change radios. Let me know if this helps.