Plug-and-Play USB FM Transmitter
USB dongle acts as a plug-in “speaker” for FM signals.
In today’s environment of on-demand audio streaming from the likes of Spotify, Apple, YouTube – or simply your own collection of stored songs – FM radio has been pushed to the wayside to some extent. At the same time, it’s still a useful bit of tech. If you’d like to combine these two worlds through your own miniature FM radio station, Redditor FirefighterDull7183 came up with a plug-and-play dongle that transmits straight from USB over the FM airwaves.
For transmission, you simply plug the FM dongle into a computer’s USB-A port, where it shows up as an audio output device. However, instead of producing sound directly, it sends an FM signal that can then be picked up by nearby radios. In theory, the device will work on Windows, Mac, and Linux, and one might see some interesting use cases for it with a Raspberry Pi SBC.
The dongle features a PCM2704 chip to receive audio from the host device (i.e. computer), which is then sent to a KT0803L chip for FM transmission. Impressively, this was FirefighterDull7183’s first design using SMD components, though it did take two board revisions to get it working.
More build information is found on the project’s GitHub page, along with a video of the device in action. Control of the output frequency and other settings is via I2C, enabled in the video by what appears to be a Raspberry Pi Pico W running CircuitPython. The board also has breakout pins for mute, volume, and suspend for easy access if needed.