Introduction: Making a Simple Spybug.

Picture of Making a Simple Spybug.

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

Picture of 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

Picture of 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

Picture of Trimmer Cap & Transistor

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

Step 4: Capacitors

Picture of Capacitors

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

Step 5: Resistors

Picture of Resistors

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

Step 6: Capacitor and Coil

Picture of 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

Picture of 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.

Picture of 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.


MehdiN8 (author)2016-08-13

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?

SorosN (author)2015-10-21

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

nidhalkratos (author)2014-06-03

Can i replace the inductor (coil) by an axial unductor ?

tutdude98 (author)2013-04-13

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

tibrahim (author)2012-08-30

i cant get a trimmer capacitor, what else can i use

anandsonu.gupta (author)2012-06-04

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

lug big lug (author)2012-02-16

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.

zack247 (author)2010-06-05

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!

cliffyd (author)zack2472010-06-05

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!

nodoubtman (author)cliffyd2012-01-16

what is a spybug?

thank you!

zack247 (author)nodoubtman2012-01-16

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.

feka (author)cliffyd2011-12-22

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.


zack247 (author)cliffyd2010-08-29

hey i found a red trimmer capacitor. will this work?

kondzio29 (author)2011-10-24

i just want to say it works.
thx man!

Eddy Dean (author)2011-09-02

what is that wire sticking out (the black one).

vignesh1230 (author)2010-08-01

I have the exact same trimmer capacitor but i have no idea how to tune/turn it. HELP Pl0x

cliffyd (author)vignesh12302010-08-15

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.

vignesh1230 (author)cliffyd2010-10-14

I meant how do u literally turn it? Like do i poke a stick in it or sumthing.

cliffyd (author)vignesh12302011-07-06

once the battery is connected it's on!

cliffyd (author)vignesh12302010-12-15

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.

robot1398 (author)2011-04-19

pic could be better

technozook (author)2011-03-18

could you please do a better pic of the scamatic cus i cant readthe right side


geo bruce (author)2011-02-15

would you upload the pcb layout so we can make our own pcb?

levettp (author)2011-01-10

How many watts does it transmit? What is range?

bobsmith760 (author)2010-06-07

I found the original version of this transmitter( and it says to use a 3v power source. I made using 9v and could not get it to work, would 3v help?

cliffyd (author)bobsmith7602010-12-15

are you sure they are the same? I will look.

bobsmith760 (author)cliffyd2010-12-15

Now that I looked again I don't think they are the same, I thought they were for some reason. I got mine working by the way, had a capacitor value off. Thanks for the help!

cliffyd (author)bobsmith7602010-06-09

Ohh man in my experience the more power the longer the range will be (I'm sure you know that) but I can't see how it would make a difference. I seriously havent seen the project done with a 3 v but I will look at the link. I think you just need to check everything to see if you have it in order or if one of your components are bad because it should work. Let me know if it made a difference.

bobsmith760 (author)cliffyd2010-06-17

I also read later that the trim cap only adjusts 2mhz and you need to stretch the coil to tune. I think this might be my problem but I cant find my transmitter at the moment so I cant tell.

cliffyd (author)bobsmith7602010-12-15

Oh yes your coil should be very close together but not touching, once you find where it is you can put wax or glue on it to prevent it from moving later on.

zack247 (author)bobsmith7602010-09-05

i think they might be different circuits, htis one has more parts to it than the other one.

bobsmith760 (author)zack2472010-09-21

That might not be the page I saw it on but I cant remember where if not there. Still lots of cool projects though : )

knex luver234 (author)2010-12-10

never mind! went ahead and made it anyway, and it works like a dream! i spent all evening building and tweaking it, got it down to where i can get perfect-near perfect reception in my entire house! hid it under my sisters bed, and heard her talkin to her BF perfectly from my room! better watch how i use it though, dont want to get in trouble....... thx for the ible!

cliffyd (author)knex luver2342010-12-15

awesome, glad it worked for you. Would not believe the people who send me messages asking what they did wrong and a lot of the time the reception will not work on expensive stereo systems and work a lot better on small little portable radios.

knex luver234 (author)cliffyd2010-12-15

agreed, i actually found that my ipod and mandheld radion work the best for my system, and not my big stereo! thats alot for posting this, i love tinkering with stuff, and this is just what i expected it to be!

ecan (author)2010-10-24

Ok, I have made the bug and have not gotten it to work. I am using a 330 ohm instead of a 360 ohm, but I have tried both. The other thing is that I'm using a 6 turn coil at 1/8 diameter screwdriver. Plz help!

cliffyd (author)ecan2010-12-15

I would concider trying it on a different radio, also try expanding and closing the coil till you find the "sweet spot" then fine tune with the trimmer cap. Other than that check to see if components are in corrent spots, no caps, backwards, mic on right?

audiLe... (author)2010-11-21

I am trying to adjust this set up to make it very very lightweight (less than 30 grams).
Is it possible to replace the battery with a smaller one (in size and weight)? say coin cells?
Some of the electronics might have to be changed I assume no? any suggestions?


cliffyd (author)audiLe...2010-12-15

oh yeah it's intirely possible. You can get away with 6 v (2 coin cells if you want i think the range will just not be as far but thats what I used on another one of my smaller bugs (3v battery from the dollar store), stock up on them.

knex luver234 (author)2010-12-10

well i have found everything,or so i hope, i had everything but the trimmer, and the other day i went to my neighbors junkjard, and found wut i think to be one, im just checking to make sure so if anyone could help, tere is some pics below. its the little ggreen thing, and it has a philips head inside, and two fee prongs coming out the bottom, r what ever you like to callem.

cliffyd (author)knex luver2342010-12-15

looks good, as long as you can change the freqeuncy you should be good.

knex luver234 (author)2010-12-12

one more question, ive got a 103 Capacitor will this work for the 1n Capacitor (102)? im wanting to make several more< so if you or someone could help!?

zack247 (author)2010-09-05

i just built it, but i cant find the signal! what did i do wrong? it running from 3v, and instead of a green trimming capacitor, i used a red one. whats wrong with it?

cliffyd (author)zack2472010-09-06

well it just depends on a number of things. You could be satanding to close to the radio (8Ft.) try moving the ant. wire around, the tuning tool your using could affect the freq. some how, the trimmer might be to small of value, or on of the coils are to far apart (wound I mean). Keep trying! If you built it to the specs you will get it to wrk it really takes patience. I also found cheap radios work better than the really expensive stereo systems. good luck keep at it!

zack247 (author)2010-07-29

whoa... i just got a epic idea. if you replace the microphone with an audio jack, you could have wireless music! you could play whatever song you like, and nobody can turn it off! could make a nice prank too...

matstermind (author)2010-07-27

are you sure that wire size is right? 6mm diameter?

Barramundi (author)2010-06-16

could you post pcb artwork

thewizard42 (author)2010-06-05

I do love how whenever i make a project in shop at school, an instructable shows up a couple days later about the very same thing i did. Good job though

Kryptonite (author)thewizard422010-06-07

Ask the teacher in advance.

thewizard42 (author)Kryptonite2010-06-13

Its a technical school and i'm taking electronics for my shop

About This Instructable




Bio: 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 ... More »
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