In this tutorial, Tom Herbison demonstrates how to use a pi as an fm radio transmitter. Please be sure to read through the guide carefully as there are numerous warnings on what not to do during the build:
The first “hack” which allowed experimenters to use the Raspberry Pi’s clock pin (GPIO 4) to transmit audio directly from the Raspberry Pi came from the Imperial College Robotics Society . Their “PiFM” module has since been modified and improved and is now capable of transmitting in 16 Bit Stereo on any frequency from about 1 MHz up to 250 MHz.
It sounds too good to be true…. so I decided to try it out for myself!
WARNING – DO NOT connect your Raspberry Pi’s clock pin (GPIO 4) to any kind of antenna (even a short length of wire) when performing any of these tests!