Signal Guide

Service Description Selection DCF77

Here you will find information about the selected service, along with measurement examples.

DCF77 Theory & Details
Typical Frequency Range:

77.5 kHz


Time signal broadcast from Mainflingen near Frankfurt

Modulation: AM

A continuous carrier signal is lowered at one second intervals. A lowering for 0.1 s indicates logical zero, a lowering for 0.2 s logical one. There is no lowering in the 59th second to indicate the start of the zero second in the next minute. Thus 59 bits of information about date, time, etc. can be transmitted every minute (seconds 0 through 58). Transmitter identification is no longer broadcast. By lowering the carrier rather than blanking it, the transmission frequency can also be used as a reference fre-quency.

DCF77 Measurement Examples
The overview measurement shows the transmission at 77.5 kHz with relatively narrow sidebands. The carrier level is reduced briefly every second
Recording over 8 seconds. The short and long dips every second corresponding to logical zero and logical one are visible.
HiRes Spectrogram Full
Gapless display over 20 s. Carrier and dips can be clearly seen.
HiRes Spectrogram Zoom
Section from the same data as HiRes Spectrogram Full. Spectrogram Full over 3 s. The time axis can be shifted as with a magnifier.
Persistence Spectrum
Based on the same data as HiRes Spectrogram Full. Shows the frequency of occurrence over 20 s.
Time domain display of a different time segment. The zero second of a new minute starts after the 2 s burst at -8 s. The symbols in the new second can be identified as: 0-0-1-0-0 ….