A professional Arduino UNO project using the SparkFun Si4713 breakout to broadcast line-level audio over FM (87.5 – 108 MHz), complete with RDS support.

• Arduino UNO (5 V)
• Si4713 FM transmitter breakout (SparkFun or equivalent)
• LM386 audio amplifier (for mic or line input)
• 3.5 mm audio jack (IN+ and IN–)
• 17 cm wire antenna
• LED + 220 Ω resistor (status indicator)
• Push-button (mute/unmute)
• Jumper wires & breadboard
• USB cable

    Arduino UNO         Si4713 Breakout        LM386 Amp         Audio Jack         Antenna
    ─────────────────────────────────────────────────────────────────────────────────────
    5V    ─► VIN       SDA ─► A4            IN+ ─► AUDIO_IN   Tip  ─► Left Channel   ─► wire
    GND   ─► GND       SCL ─► A5            IN– ─► AUDIO_IN   Ring ─► Right Channel  ─► GND
    ANT   ─► ANT       OUT ─► LM386_OUT  Sleeve (ground)
    Button ─► D2 (INPUT_PULLUP, press to GND)
    LED    ─► D6 (via 220 Ω resistor to GND)

1. Install the SparkFunSi4713 library via Arduino Library Manager.

2. Open Serial Monitor at 115200 baud.

3. Send commands:

    F <MHz>  — set frequency (e.g. `F 99.7`)
    V <0–63> — set volume level
    P <PS>   — set 8-char RDS Program Service name
    T <RT>   — set RDS Radio Text (max 64 chars)
    S        — show current settings
   

4. Feed audio into the LM386 amplifier.

5. Tune your FM receiver to the chosen frequency.

Note: Always check local regulations before transmitting on FM band.