Teensy 4.x FM Stereo+RDS Transmitter for experimentation

Frank B

Senior Member
DON'T CONNECT AN ANTENNA OR EVEN A WIRE. THAT'S NOT ALLOWED.
USE A SHIELDED CABLE TO YOUR RADIO.


TeensyFMTransmitter
So, finally, it works with all wanted features.
The Teensy 4 PLLs are capable to lock in very short time, and I thought that could be used to create a FM transmitter.
It uses the Video PLL to generate a modulated frequency between 88..107 MHZ (not all frequencies work)
The sound quality is very OK, and it transmitts Radio Text and the Program-name via RDS.
The code can be used as part of the audio-library. The provided examples connect the normal Audio-Lib wave-player to the transmitter, which is used as output.
The internal samplerate is about ~353kHz.
The preferred output-pin is 33.
No additional hardware needed. Not even a wire. Just a pure Teensy (4.1 to use the builtin SD Slot for wave-files)

Use it for experiments only, and make sure that it is shielded.
Can be used to test your homemade radio, for example.

With special thanks to DD4WH.

Footnote:

Legal note:
TeensyFMTransmitter is an experimental program, designed only for experimentation.
It is in no way intended to become a personal media center or a tool to operate a radio station,
or even broadcast sound to one's own stereo system.
In most countries, transmitting radio waves without a state-issued licence specific
to the transmission modalities (frequency, power, bandwidth, etc.) is illegal.
Therefore, always connect a shielded transmission line from the Teensy directly to a radio receiver,
so as not to emit radio waves. Never use an antenna.
Even if you are a licensed amateur radio operator, using TeensyFMTransmitter to transmit
radio waves on ham frequencies without any filtering between the Teensy and an antenna is most probably illegal

because the square-wave carrier is very rich in harmonics, so the bandwidth requirements are likely not met.
I could not be held liable for any misuse of your own Teensy.
Any experiment is made under your own responsibility.



@Paul: No Photo, as it is just the bare Teensy.
 
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