(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 (0.1s=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.

