Building a Simple FM Radio Receiver

Built an FM receiver using the TEA5767 module and an Arduino. The TEA5767 is a complete FM tuner in a single IC with I2C control — you write the desired frequency in MHz as a 14-bit PLL word and it tunes.

The formula for the PLL word: for 87.5-108MHz FM band, PLL = (frequency × 4 + 225kHz × 4) / 32.768kHz. In practice the datasheet example code gets it right. The TEA5767 has a signal strength indicator register (RSSI) that makes basic channel scanning trivial — sweep the band in 100kHz steps, read RSSI at each, and identify peaks.

Audio output is a differential analog signal from pins 8 and 9. For direct speaker output, a small class D amplifier IC (PAM8403) works well. For headphone output, the differential signal can feed directly into a headphone jack with the common connected to a mid-rail voltage divider — the TEA5767 output is 75mV RMS which is enough to drive most headphones.