Last year, I decided to build a word watch with ePaper display and time announcement. The real challenge was to achieve synchronization with the atomic clock in Braunschweig (Germany) using the DCF77 time signal transmitter, a long-wave transmitter at 77.5 kHz near Frankfurt/Main.
Standard receiving coils are about 60 mm long and have a diameter of 10 mm.
After some experimentation and careful adjustment of the resonance frequency, I succeeded in receiving the signal by abusing four chip inductors (Murata LQH43NH222J03L) 2.2 mH, which are intended for applications such as power supplies, boost converters, etc. Synchronization takes one minute, during which the hour, minute, calendar day, day of the week, month, and year are transmitted, and only works when the clock is stationary (overnight).
During a vacation, synchronization worked as far as San Sebastian (Spain), which is over 1300 km away!
I know the watch looks terribly ugly, it's only an experiment