This simple hack turns your Raspberry Pi into a powerful FM transmitter! It has enough range to cover your home, DIY drive-in movie, a high school ball game, or even a bike parade (depending on the stragglers).
PiFM software not only boldly enhances the capability of your Pi, but does so with nothing more than a single length of wire. This hack starts with the absolute minimum you need to run a Raspberry Pi — an SD card, a power source, and the board itself — and adds one piece of wire. It’s the coolest Pi device we’ve ever seen with so few materials.
PiFM was originally created by Oliver Mattos and Oskar Weigl, and revised by Ryan Grassel. We’d like to thank the whole PiFM community for inspiration. MAKE’s contribution to the project, the PirateRadio.py script, now enables playback without using the command line, and handles all the most common music file formats automatically. It was written by MAKE Labs engineering intern Wynter Woods. You can find the source code here.
NOTE: The Raspberry Pi’s broadcast frequency can range between 1Mhz and 250Mhz, which may interfere with government bands. We advise that you limit your transmissions to the standard FM band of 87.5MHz–108.0MHz (see Step 3) and always choose a frequency that’s not already in use, to avoid interference with licensed broadcasters.
Step #1: Make the antenna.
- Technically, all you need for an antenna is a piece of wire. For an optimal antenna, you could attach a 75cm wire to pin 4, with a 75cm power cable pointed in the other direction. (That would effectively make a half-wave dipole antenna at 100MHz, near the middle of the FM band.) We just used 40cm of 12 AWG solid wire, since things started tipping over when the wire got longer.
- Cut and strip a female jumper wire. Solder it to one end of your antenna, and insulate with heat-shrink tubing.
- Dab hot glue around the joint for support, and stick it on pin 4 of the GPIO pins of your Raspberry Pi. The glue makes the antenna more rigid so it stands up better.
- NOTE: If you have the Raspberry Pi Starter Kit and you’re in a hurry, you can just use a male jumper wire plugged into the Cobbler breakout board! (Both are included in the kit.) It will work, but the range will be roughly half of what you’d get with 40cm of 12 AWG solid copper.
For more detail: Raspberry Pirate Radio