Rocode >> Hobbies >> FMTransmitter

FM Music Transmitter

This page details an FM Transmitter.

Such USB FM Transmitters may be purchased on ebay for $10.

We connect the miniature USB FM Transmitter to a Raspberry Pi that costs $49.

A usb port is used to supply power and the audio cable is connected to the audio jack on the Raspberry Pi.

The USB FM Transmitter set to 108.0 FM

The FM Transmitter may select a frequency between 87.5MHz and 108.0MHz in 0.1MHz steps.

108.0MHz has been selected as this frequency is unused here in Melbourne.

A SONY boom box is tuned to 108.0MHz to listen to the output of the FM Transmitter.

SONY Boom Box on 108.0MHz

Music Playlist Scripts

Using some simple scripts a play list of songs is played in random order to the FM Transmitter.

I have taken the code from that generates random line from a file.

The script:

Take random line script

Put the tracks of your playlist in selected.playlist.

List of tracks goes in selected.playlist

To change playlists just overwrite your playlist in selected.playlist.

The script that selects a track and plays it is

Player script

Using a copy of the song name is also output on connected LED Matrix displays.

LED matrix notification script

Here is the LED Matrix with a Planetshakers Reflector CD track being played

Example LED Display Output

Software Defined Radio

Next a RTL-SDR Software Defined Radio on Linux is tuned to 108.0MHz.

On the spectrum graph you will see the Melbourne Triple J FM station on 107.5MHz and the FM Transmitter on 108.0MHz.

The following screen shots show the FM Transmitter at Loud, Moderate, Soft and Silent volumes.

Spectrum Display for Loud Transmitter

It is noticed that using a Loud volume the transmitter will spread more widely and less uniformly to the sides of its spectrum space.

Spectrum Display for Moderate Transmitter

Spectrum Display for Soft Transmitter

Spectrum Display for Silent Transmitter