μWWVB: A Tiny WWVB Station

μWWVB is a DIY watch stand that emulates the WWVB atomic clock radio signal to automatically synchronize radio-controlled wristwatches where the real WWVB signal is unavailable. The project uses an ATtiny44A microcontroller, a GPS module for accurate time acquisition, and a repurposed ferrite antenna to broadcast a 60 kHz amplitude-modulated signal. The author covers PCB design and milling, firmware written in plain C (including NMEA GPS parsing, DST calculation, and PWM-based carrier generation), 3D-printed and laser-cut enclosure design, and FCC regulatory compliance. The result consistently synchronizes a watch within about three minutes to ~500ms UTC accuracy.