In addition to the amplitude modulation (AM), a pseudo-random phase noise is modulated onto the carrier of DCF77. For this purpose, the phase is shifted in accordance with a binary random sequence by ±13°, the mean value of the carrier phase remaining unchanged. At the reception side, the pseudo-random sequence used can be reproduced as a search signal and cross-correlated with the phase noise contained in the DCF77 signal received. This allows the arrival times of the time signals received to be determined more precisely.
Details can be obtained on request.