(Original in German available from the address below. Translation errors courtesy of Peter Lamb, Swiss Fed. Inst. of Technology)
Physikalisch-Technische Bundesanstalt (PTB) Braunschweig, Febuar 1984
Lab 1.21
Bundesalle 100
D-3300 Braunschweig
Legal basis and responsibility for the transmissions from DCF77
The 1978 law on time standards defines legal time in Germany on the
basis of Coordinated World Time (UTC) and gives the PTB responsibility
for the keeping and broadcasting of legal time. As well as this, the
time standards law empowers the Federal government to issue regulations
for the introduction of Summer Time.
Legal time in the FRG is either Middle European Time (MEZ - German
abbreviation) or, in case of its introduction Middle European Summer
Time (MESZ). The following relationships hold between UTC and MEZ and
MESZ.
MEZ(D) = UTC(PTB) + 1h
MESZ(D) = UTC(PTB) + 2h
Legal time is generated in the PTB Atomic Clock Building in Braunschweig
and it is broadcast mainly through the LF transmitter DCF77 which the
PTB rents from the German Post Office (DBP). The PTB has sole
responsibility for the control of DCF77, while the DBP has
responsibility for the transmitter and antennas. Queries should be
directed to the above address or by telephone to 0531/592 1212 or
0531/592 1210, or by telex to 952822 ptb d.
DCF77 Specifications
Location: Mainflingen transmitter complex, (50:01N, 09:00E), about
25km south-east of Frankfurt a. Main.
Carrier Frequency: Standard frequency 77.5kHZ, derived from the PTB
atomic clocks. Relative deviation of the carrier from
specifications:
averaged over 1d: <1e-12
averaged over 100d: <2e-13
The carrier phase is controlled so that deviations
relative to UTC(PTB) are never greater than +-0.3us.
Larger phase and frequency variation observed at the
receiver are due to summation of ground and space waves.
Power output: Transmitter power 50kw, estimated emitted power approx.
25kW.
Antenna: 150m high (backup antenna 200m high) vertical
omnidirectional antenna with top capacitance.
Transmission times: 24-hour continuous service. Short interruptions (of
a few minutes) are possible if, because of technical
problems or servicing, the service must be switched to a
backup transmitter or antenna. Thunderstorms can cause
longer interruptions to the service.
Time signal: The carrier is amplitude-modulated with second marks. At
the beginning of each second (with the exception of the
59th second of each minute), the carrier amplitude is
reduced to 25% for the duration of either 0.1 or 0.2
seconds. The start of the carrier reduction marks the
precise beginning of the second. The minute is marked by
the absence of the previous second mark.
The second marks are phase-synchronous with the carrier.
There is a relatively large uncertainty possible in the
time of the second mark which depends on the receiver
position. The causes are the relatively low bandwidth of
the antenna, space wave and other interference sources.
Despite this, it is possible to achieve accuracy better
than 1ms at distances of several hundred kilometers.
Time code: The transmission of the numerical values for minute,
hour, day, weekday, month and year are BCD-encoded
through the pulse duration modulation of the second
marks. A second mark with duration 0.1s encodes a binary
0 and a duration of 0.2s encodes 1. The order of encoding
is shown in the following diagram [replaced by a table in
this translation]. The three test bits P1, P2 and P3
extend the 3 major sections of the time code (7 bits for
minutes, 6 bits for the hour and 22 bits for the date,
including the week day number) to maintain an even count
of 1's.
The second marks No. 17 and 18 indicate the time system
for the transmitted time codes. In the case of
transmission of MEZ, mark 18 has a duration of 0.2s and
mark 17 a duration of 0.1s. If MESZ is being transmitted,
this is reversed. Furthermore, an approaching transition
from MEZ to MESZ or back is announced by extending mark
16 from 0.1 to 0.2s for one hour prior to the changeover.
Encoding Scheme [diagram in original]
Mark number(s) Encodes (01.s=0, 0.2s=1)
0 Minute, always 0 (0.1s)
1-14 Reserved
15 0=Normal antenna, 1=backup antenna
16 1=Approaching change from MEZ to MESZ or back
17,18 Time zone 0,1=MEZ; 1,0=MESZ
19 The leap second is encoded in this bit one hour prior to
occurrence.
20 Start bit for encoded time, always 1
21-27 1, 2, 4, 8, 10, 20, 40 Minutes (mark 21=1 minute)
28 P1 maintains even parity for marks 21-28
29-34 1,2,4,8,10,20 Hours (mark 29=1 hour)
35 P2 maintains even parity for marks 29-35
36-41 Day in month (1, 2, 4, 8, 10, 20)
42-44 Day in week (1,2,4)
45-49 Month number (1, 2, 4, 8, 10)
50-57 Year (1, 2, 4, 8, 10, 20, 40, 80)
58 P3 maintains even parity for marks 36-58 There is no mark
transmitted for the 59th second.
Literature
P. Hetzel, "Die Zeitsignal- und Normalfrequenzaussendungen der PTB ueber
den Sender DCF77: Stand 1982" [The PTB time signal and standard
frequency transmissions from DCF77: Status 1982] in "Funkuhren" [Radio
clocks], W. Hilberg, Oldenburg Publishers, Munich & Vienna 1983, pp 42-
57.
G Becker & P. Hetzel, "Vortraege ueber DCF77" [Lectures: DCF77], PTB
Reports, PTB-Me-23 (1979), pp 185-253. Braunschweig 1984
Additional information: DCF77
Since July 1983, the DCF77 carrier has been phase modulated in a test
configuration. The phase modulation is a pseudorandom binary sequence
sent twice each second. The clock frequency of the binary sequence is
645.833...Hz and the phase shift \Delta\tau about 3% of the period
(\^{=} 10\deg). Equal numbers of shifts of +\Delta\tau and -\Delta\tau
are always sent, so that the mean frequency remains unchanged, and the
use of DCF77 as a frequency standard is unaffected. The timecode is
encoded in the sequence by inverting the sequence or not. Not inverted
sequence corresponds to a 0 bit. The sequence is alleged to be generated
by a 9 bit shift register which is coupled back on positions 5 and 9.
The polynomial might be: x^9 + x^4 + 1.
Because the pseudo-random bitstring has a strictly deterministic nature,
the correlation analysis at the receiver end leads to a correlation
function with triangular form, and thereby to timing information. Early
test results show that the time information received with the help of
pseudo-random phase modulation is more resistant to interference and
more accurate (standard deviation \approx 10\mu s during the day and
\approx 25\mu s at night) than the conventional method using amplitude
modulated second marks. Since this new modulation method is compatible
with previous usage of DCF77, and that the users have made no
difficulties known to us, the tests have been extended. The transmission
of the pseudo-random phase distortion still has experimental status, and
should not be seen as a permanent commitment. Further information will
be made available in the future.
Announcement bit for a leap second
The DCF77 control unit is currently being modified so that in future an
announcement bit for a leap second can be sent. It is expected that for
the first time on 1st July 1985 the second mark Nr. 19 will be extended
to a length of 0.2s for one hour prior to the introduction of a leap
second. Intelligent receivers will then be able to recognise the
discontinuity and maintain correct indicated time in spite of a 61s
minute.
Availability
The clock was made by a local radio amateur.
Empfangsanlage DCF77 (SFr 690. complete, also available in kit form)
Walter Schmidt
Eichwisrain 14
8634 Hombrechtikon
Switzerland
LF reciever and decoder for the German time standard DCF77. As yet
untested. Has a 1s impulse output driven direct from the reciever, which
could be used in a similar manner to the pulse output on the Spectracom.
Internal crystal-controlled clock reset each minute by the DCF77 minute
mark. Indication available to program of whether currently synchronised,
and a count of how long since the last synchronisation is available if
running unsynchronised. Returns time with resolution 0.1s, but probably
synchronised to the time of command reception, and not to the 0.1s
counter. I will try to get the firmware changed if this is the case.
Other sources
Die folgende Liste ist einer Information der PTB entnommen. Fuer evtl.
Tippfehler wird nicht gehaftet (;-) (Umlaute sind in ASCII Umschrift
(ae,oe,ue,ss) dargestellt.)
Am 1 Juli 1993 wurde diese Liste auf die neuen Postleitzahlen
umgestellt. Die alten Postleitzahlen stehen in runden Klammern - einige
konnten nicht korrigiert werden (Korrekturen werden gerne angenommen).
Bei Erweiterungen/Aenderungen bitte email an time@informatik.uni-
erlangen.de
Note: This document was corrected for the new zip codes on July 1st
1993. The old zip codes are in parenthesis. Some zip codes could not be
converted.
Last update: 91/06/05 - 13:34:36
Januar 1989 (PTB Original)
Hersteller/Vetriebsfirmen von DCF77-Empfangsgeraeten
----------------------------------------------------
1. Funkuhren fuer Zeitdienst-Systeme (z. B. Funkuhren fuer Uhren-
anlagen und Turmuhr-Zentralen; modulare Funkuhren mit RS 232-
Schnittstelle fuer Rechner; funkgesteuerte Schaltuhren, Zeit-
kodegeneratoren und Aussenuhren)
kodegeneratoren und Aussenuhren)
Auerswald GmbH & Co. KG Vor den Grashoefen 1
Tel.: 05306/92000 38162 (3302) Cremlingen,
OT Schandelah
Electronic Design Buero Zeilstrasse 56
Herwig Braun GmbH 72793 (7417) Pfullingen
Tel.: 07121/71560
Ferrari electronic GmbH Beusselstrasse 27
Tel.: 030/3965021 10553 (1000) Berlin (21)
Gesellschaft fuer Datensysteme (GDS) Hindenburgstrasse 13
Tel.: 05306/7010 38162 (3302) Cremlingen
OT Schandelah
Heliowatt Werke Wilmersdorfer Str. 39
Elektrizitaets-Gesellschaft mbH 10627 (1000) Berlin (12)
Tel.: 030/31908-01
Hopf Elektronik Postfach 18 47
Tel.: 02351/45038 58468 (5880) Luedenscheid
Philip Hoerz Moltkestrasse 6
Turmuhren 89077 (7900) Ulm
Tel.: 0731/37168
Marcel Kreutler Postfach 37 44
Zeit- und Informationstechnik 67050 (7500) Karlsruhe (1)
Tel.: 0721/85281
Landis & Gyr GmbH Friesstrasse 20 - 24
Tel.: 069/40020 60388 (6000) Frankfurt (60)
Lennartz Elektronic GmbH Bismarkstrasse 136 - not translated
Tel.: 07071/3088 (7400) Tuebingen
Werner Meinberg Elektronik Auf der Landwehr 22
Tel.: 05281/2018 31812 (3280) Bad Pyrmont
Aus dem Moore Postfach 21 41
Turmuhr-Elektronik 32361 (4994) Preussisch
Tel.: 05742/5225 Oldendorf 2
Moser-Baer AG CH-3454 Sumiswald
Tel.: 0041/34/721144 Schweiz
Noelpp-Informationssysteme GmbH Friedensstrasse 41
Tel.: 06101/87592 61118 (6368) Bad Vilbel (2)
Heinrich Perrot Postfach 13 51
Turmuhrenfabrik 75353 (7260) Calw-Heumaden
Tel.: 07051/12055
Precitel SA Avenue du Mail 59
Tel.: 0041/38/247555 CH-2000 Neuchatel
Schweiz
Georg Rauscher Wuerzburgerstrasse 4
Turmuhrenfabrik 93059 (8400) Regensburg
Schwille-Elektronik Benzstrasse 1
Tel.: 089/9031041 85551 (8011) Kirchheim
Siemens AG Postfach 53 29
Tel.: 0511/1290 30053 (3000) Hannover (1)
Telefunken electronic Ringlerstrasse 17
Tel.: 0841/8811 85057 (8070) Ingolstadt
Telenorma Uhren GmbH Postfach 44 32 - not translated
Tel.: 069/266-1 (6000) Frankfurt (1)
ZERA Elektronische Pruefgraete Postfach 11 60
Cremer & Co. 53621 (5330) Koenigswinter
Tel.: 02223/22075
2. Funkuhren fuer den haeuslichen Gebrauch (z. B. Tisch- und Wand-
uhren der Firmen Dugena, Hermle, Junghans, Kundo,...)
Vertrieb durch den Uhrenfachhandel und die Fachabteilungen
von Kauf- und Versandhaeusern
3. Funkuhr-Bausaetze und -Fertiggeraete
Vertrieb durch den Elektronik-Fach- und Versandhandel
4. DCF77-Normalfrequenzempfaenger und Frequenzregler fuer Normal-
frequenzoszillatoren
Goerl HF-Messtechnik Buchenstrasse 2
Tel.: 0821/482613 86356 (8902) Neusaess 4
Rohde & Schwarz Muehldorfstrasse 15
Tel.: 089/4129-0 81671 (8000) Muenchen (80)
0911/86747 (Nuernberg)
Unverdross Technik Tutzinger Hof Platz 6
Tel.: 08151/21198 82319 (8130) Starnberg
Die mit `*' gekennzeichneten Firmen unter 1. haben neben Funkuhren auch
DCF77-Normalfrequenzempfaenger in ihrem Vertriebsprogramm.
Diese Liste wurde erstellt aufgrund von Informationsmaterial, das der
PTB ueber DCF77-Empfangsgeraete vorliegt. Falls neue Produkte auf den
Markt kommen, eine Firma uebersehen wurde oder eine hier aufgefuehrte
Firma die Produktion von DCF77-Empfangsgeraeten einge-stellt hat, bittet
die PTB um Zusendung von entsprechenden Infor-mationen, damit diese
Zusammenstellung aktualisiert werden kann.