PiFm- Learning To Transmit

At the heart of every radio station there is the transmitter. This is used to transmit your music and prerecorded shows to the world, or at least your neighborhood. The Raspberry Pi is the perfect transmitter for a localized radio station for several key reasons;

1. Size- with both the computer housing the audio and the transmitter built into a form the size of a credit card, you can put up a radio station anywhere there is power in under a minute. 
2. Cost- at $35 for the Raspberry Pi V2, the Raspberry is definitely the most cost effective solution on the market for a beginner to radio.
3. Ease of use- Built on the open source Linux platform, any number of modifications can be made to the source code, and an intuitive GUI makes things easier then ever.

They key to transmitting on the FM spectrum is PiFm, a program made by the Imperial College Robotics Society at a code hack fest. The official wiki for the project can be viewed here, but I will be covering all the steps needed to use PiFm in a much easier way.

When you have constructed an antenna, connect it to your GPIO 4 pin. Click this to download the PiFm package to your raspberry pi. Save it to your home directory and unpack it there. That's it! PiFm comes with a sound.wav file so that you can start using it right away. To make sure that you installed PiFm correctly, open up a new terminal window and type

sudo ./pifm sound.wav 100.0

This will play sound.wav at 100mhz. If you tune a radio to that frequency, you should hear the star wars theme song playing! Good job! It is important to know that in most areas, 100.0FM will be used by an existing radio station. To change the frequency, simply change the 100.0 to any frequency that is open. For example

sudo ./pifm sound.wav 87.9

That is the frequency that I use. If you want to change the file that is playing, simply change sound.wav to the file name. The file does have to be in the home directory- were you unpacked PiFm.