This project is a mini FM bug build using spare parts of a mobile phone. The range of this FM bug is around 1km with full CR2032 battery and good conditions. You can download schematics on the link below.
FM bug 420-480 MHz – [Link]
lucidscience.com has build a 2 transistor Spy Transmitter that will send the sounds picked up in a room to any FM radio tuned to the same frequency as the transmitter. Check construction details on the link below. [via]
This project is focused towards those who have not yet attempted to build any kind of RF project, and it is laid out in such a way as to make it easy to explore the basic principles of RF circuitry and ensure a successful final product.
Tiny 2 transistor Spy FM Transmitter – [Link]
This circuit is a circuit diagram fm transmitter. Transmitter circuit described here has the additional RF power amplifier stage, after the oscillator stage, to increase the power output of 200-250 milliwatts. With a good matching 50-ohm ground plane antenna or multi-element yagi antenna, this transmitter can provide a good enough signal strength to a distance of about 2 kilometers.
Long Range FM Transmitter Circuit – [Link]
This project shows how to convert a simple FM transmitter to a miniature TV transmitter. Just change the input from the audio to the video (video camera or VCR) and check the signal at your television set. In Europe, for instance, choose the channel 2 – 4 and turn the trimmercap of the transmitter until you see a clear image.
Micro TV transmitter - [Link]
This FM transmitter (FM Tx) is about the simplest and most basic FM Tx it is possible to build and have a useful
transmitting range. It is surprisingly powerful despite its small component count and 3V operating voltage. It will
easily penetrate over three floors of an apartment building and go over 300 meters in the open air. The circuit
we use is based on a proven Australian design.
Simple FM Transmitter – [Link]
This is a small but quite powerful FM transmitter having three RF stages incorporating an audio preamplifier for better modulation. t has an output power of 4 Watts and works off 12-18 VDC which makes it easily portable. It is the ideal project for the beginner who wishes to get started in the fascinating world of FM broadcasting and wants a good basic circuit to experiment with.
4 Watt FM Transmitter – [Link]
This Phone FM transmitter connects in series to your telephone line and transmits the telephone conversation over the FM band when you pick up the telephone handset. Transmitted signal can be tuned by any FM receiver. The circuit includes an “On Air” LED indicator and also provides a switch which can be used to turn off the transmitter.
Phone FM Transmitter - [Link]
This is the basic fm trasmitter that I built. In theory, according to electronics, it shouldn’t work but works fine and is very sensitive. It can transmit the signal up to 45 yards (about 40 meters) . A sensitive FM radio can pick up the signal up to 100 yards (80 meters) but I can’t see any reason for it.
This kind of microphones are also called “spy microphones” but knowing that the battery is bigger than the actual circuit, I can’t see any application like that, anyway, this circuit should be used as educational application only.
Micro FM transmitter - [Link]
Here is a stereo FM Transmitter based on BH1415F wireless audio link IC. Phase Locked Loop controller use Microchip PIC16F628 and the the PLL frequency programming can be displayed with 8×2 and 16×2 LCD display.The frequency range can adjustable from 88-108 MHz.
Stereo FM Transmitter BH1415F – [Link]