The most surprising detail here is that the receiver circuitry inside a Wi-Fi chip can pull broadcast FM off the air at all. Veryokay wired an ESP32-S3 up as the IF stage behind a moRFeus upconverter, and the on-chip spectrum mode covers 40 MHz, wide enough to show the entire FM band in a single sweep in SDR++.
The frequency plan is neat. The S3 only tunes 2.2 to 2.8 GHz, well above the broadcast band, so the upconverter shifts stations up into that window. With the moRFeus local oscillator set to 2259.1 MHz, the 90.9 MHz station lands at 2350 MHz. To feed it properly, the maker cut the onboard antenna and fitted a coax pigtail to the board. Firmware is the open-source ESPARGOS ESP-SDR package, with SDR++ handling the display and IQ mode doing the FM demodulation. The source selector sits on SDRplay RSPdx with WFM picked.
There are real measurements too. Narrowband FM at 2.35 GHz came in at 12 dB SINAD near -113 dBm, and strong signals reached about 42 dB SINAD. Receiver testing was done on coax with a Signal Hound VSG60, which is more rigor than most hobby work ever sees. The SDR++ driver and an Android build are open source as well.
One thing stays open: there is no word on whether shielding was added to keep surrounding Wi-Fi traffic from getting in the way. Meanwhile the maker reports still listening and says the audio of the station sounds very nice.
Project by Veryokay. Watch it on their YouTube channel: