https://learn.adafruit.com/adafruit-si4713-fm-radio-transmit...
John Park did a short video on it https://www.youtube.com/watch?v=PKP6Z-cEbFQ
You can also buy a fully legal MP3 FM transmitter. https://radiofidelity.com/best-fm-transmitter-for-your-car/
Bitluni made a fun (illegal) AM radio transmitter with an esp32 https://youtu.be/lRXHd3HNzEo
So you can get radio when there is no cell or data service - like when camping or hiking etc.
You set the sound card output at your OS settings and everything it's broadcasted over FM.
I know some of them exist for bluetooth audio, but not for FM.
- a USB sound card with 3.5mm jack, and
- an FM transmitter module (which can usually be powered with 3v-12v, so should be able to work with 5v USB power
(If I wasn't already neck deep in interesting challenges I would consider picking this one up)
It provides a good signal, is easy to adjust, and works well for phone calls (not just music).
Sorry, I don't know. It's in my parents' car, so I won't be able to check until the next time I visit them.