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 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.
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 http://crunchbang.org/forums/viewtopic.php?id=4294 that generates random line from a file.
The random.sh script:
Put the tracks of your playlist in selected.playlist.
To change playlists just overwrite your playlist in selected.playlist.
The script that selects a track and plays it is musicplayer.sh:
Using musicled.sh a copy of the song name is also output on connected LED Matrix displays.
Here is the LED Matrix with a Planetshakers Reflector CD track being played
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.
It is noticed that using a Loud volume the transmitter will spread more widely and less uniformly to the sides of its spectrum space.