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.