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PPENDIX
System 6844(RC) - V03.00
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hopf
Elektronik GmbH
Nottebohmstr. 41
• D-58511 Lüdenscheid • Tel.: +49 (0)2351 9386-86 • Fax: +49 (0)2351 9386-93 • Internet: http://www.hopf.com • E-Mail: [email protected]
12.3.1.2 Advantages and Disadvantages DCF77
+
DCF77 receivers are generally less expensive than GPS receivers
+
Reception of the legal time in Germany
+
The antenna can be installed inside a building under favorable conditions
(no lightning protection or expensive laying of antenna cable is necessary)
–
Sensitive to interference signals
(atmospheric interference or radiation from electric motors, monitors or other
switched, inductive loads)
–
Installation limited to within approx. 1500km of Frankfurt, Germany
–
Transmitter may be switched off when there is bad weather at the transmission
location
–
Lower short-term accuracy when compared with GPS
12.3.2 DCF77 Generation by
hopf
Clocks
hopf
clocks can simulate the DCF77 signal for other clocks in order to operate DCF77
clocks in locations where the DCF77 signal is not available.
This can realized as DCF77 antenna simulation (77.5kHz) and also as DCF77 pulse (1Hz).
12.3.2.1 DCF77 Signal Simulation
An analogue, amplitude-modulated carrier signal is generated by the clock system. A con-
nected, standard DCF77 radio-controlled clock is unable to differentiate this signal from an
"original" DCF77 signal received via an antenna. It is also possible to use time bases other
than only CET/CEST to simulate the signal.
The term
DCF77 Antenna Simulation
or, in short,
DCF77 Sim
is commonly used in
hopf
literature to describe this term.
12.3.2.2 DCF77 Pulse (1Hz)
The DCF77 pulse uses the same coding procedure as that used by the DCF77 signal radiat-
ed by the transmitter. The difference lies in the fact that an amplitude-modulated carrier sig-
nal is not used for transmission. The 100 and 200msec. long reductions are represented by
logical signal levels.
In this digital form the signal can then also be transmitted via a fiber optic cable, for example.
