RF Time Sync
Time Syncs¶
DCF77¶
Transmited at 77.5kHz
Original Casio Time sync over RF. The DCF77 (Germany) signal is a carrier, that is amplitude modulated with attenuation every second of the minute except the 59th to synchronize. The length of the attenuation (100ms and 200ms) denotes bit values 0 and 1 respectively so in each minute, 59 bits can be transferred, containing date and time information.
https://www.rtl-sdr.com/a-gnu-radio-dcf77-time-signal-decoder/
https://en.wikipedia.org/wiki/DCF77