Meinberg PZF511 User Manual

Technical Information

Operating Instructions

PZF511

Impressum

Meinberg Funkuhren GmbH & Co. KG
Lange Wand 9
D-31812 Bad Pyrmont

Phone: [phone] / 9309-0
Fax: [phone] / 9309-30

Internet: http://www.meinberg.de
Email: [e-mail]

February 24, 2010

Table of contents

General information .............................................................................. 5

Features PZF511 .................................................................................. 6

Installation PZF511 .............................................................................. 7

Operating voltage ........................................................................ 7

Antenna ....................................................................................... 7

Assembly of antenna.......................................................... 7

Front panel ............................................................................................ 8

Pilot lamps ............................................................................................ 8

Display ................................................................................................. 9

Control keys ......................................................................................... 9

Menu items ........................................................................................... 9

Menu TIME ................................................................................ 9

Menu DATE ............................................................................. 10

Menu DAY o.W. ...................................................................... 10

Menu PZF STAT ...................................................................... 10

Menu FIELD............................................................................. 11

Menu SETUP............................................................................ 11

Menu DIST. o. T ............................................................. 11

Menu SYNTH. ................................................................ 12

Menu SYNTH M. ........................................................... 12

Menu TIME REF ............................................................ 12

Menu PAR.COMx .......................................................... 13

Menu SER.MODE .......................................................... 13

Menu STR.COMx ........................................................... 13

Menu IRIG ...................................................................... 14

Menu IRIG REF .............................................................. 14

Menu OSZ.ADJ. ............................................................. 15

Menu DAC CLR ............................................................. 15

Menu SER. No. ............................................................... 15

Asynchronous serial interfaces ........................................................... 16

Pulse outputs ....................................................................................... 16

Standard frequencies ........................................................................... 16

Frequency synthesizer ........................................................................ 17

Timecode ............................................................................................ 17

Abstract ..................................................................................... 17

Block Diagram Timecode ......................................................... 18

IRIG Standard Format ............................................................... 19

AFNOR Standard Format ......................................................... 20

Assignment of CF Segment in IEEE1344 Code ....................... 21

DC and AM Timecodes ............................................................ 22

Sine Wave AM Output .................................................... 22

PWM DC Output............................................................. 22

DCF77 Emulation .............................................................................. 22

Realtime clock .................................................................................... 23

TIME_SYN output ............................................................................. 23

Firmware updates ............................................................................... 24

Replacing the lithium battery .............................................................. 24

CE Label ............................................................................................ 24

Technical specifications ...................................................................... 25

PZF511 with different oscillator options ................................... 27

Time Strings .............................................................................. 28

Format of the Meinberg Standard Time String................. 28

Format of the ATIS standard Time String........................ 29

Format of the Uni Erlangen String (NTP)........................ 30

Signal description PZF511 ........................................................ 32

Rear Connector Pin assignment................................................. 33

Menüstruktur PZF511 ........................................................................ 35

General information

The German long wave transmitter DCF77 started continious operation in 1970. The
introduction of time codes in 1973 build the basic for developing modern radio remote
clocks.

The carrier frequency of 77.5kHz is amplitude modulated with time marks each
second. The BCD-coding of the time telegram is done by shifting the amplitude to 25%
for a period of 0.1s for a logical '0' and for 0.2s for a logical '1'. The receiver reconstructs
the time frame by demodulating this DCF-signal. Because the AM-signal is normally
superimposed by interfering signals, filtering of the received signal is required. The
resulting bandwidth-limiting causes a skew of the demodulated time marks which is in
the range of 10ms. Variations of the trigger level of the demodulator make the accuracy
of the time marks worse by additional +/-3ms. Because this precision is not sufficient for
lots of applications, the PTB (Physical and Technical Institute of Germany) began to
spread time informations by using the correlation technique.

The DCF-transmitter is modulated with a pseudo-random phase noise in addition to
the AM. The pseudo-random sequence (PZF) contains 512 bits which are transmitted by
phase modulation between the AM-time marks. The bit sequence is build of the same
number of logical '0' and logical '1' to get a symmetrical PZF to keep the average phase of
the carrier constant. The length of one bit is 120 DCF-clocks, corresponding to 1,55ms.
The carrier of 77.5kHz is modulated with a phase deviation of +/-10° per bit. The bit
sequence is transmitted each second, it starts 200ms after the beginning of a AM second
mark and ends shortly before the next one.

Compared to an AM DCF77-receiver, the input filter of a correlation receiver can be
dimensioned wide-bandwidth. The incoming signal is correlated with a reconstructed
receiver-PZF. This correlation analysis allows the generation of time marks which have
a skew of only some microseconds. In addition, the interference immunity is increased
by this method because interference signals are suppressed by averaging the incoming
signal. By sending the original or the complemented bit sequence, the BCD-coded time
information is transmitted.

The absolute accuracy of the generated time frame depends on the quality of the
receiver and the distance to the transmitter, but also on the conditions of transmission.
Therefore the absolute precision of the time frame is better in summer and at day than in
winter and at night. The reason for this phenomenon is a difference in the portion of the
sky wave which superimposes the ground wave. To check the accuracy of the time
frame, the comparison of two systems with compensated propagation delay is meaning­ful.

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Features PZF511

The PZF511 is a high precision receive module for the DCF77-signal build in eurocard
size (100mm x 160mm). The 61mm wide front panel contains an eight digit alphanume­ric display, three LEDs and two keys as control actuators.

The microcontroller of the system correlates its receiver-PZF with the incoming
pseudorandom sequence and decodes the time information of the DCF-telegram simulta­neously. The controller handles input and output functions of the PZF511 and synchro­nizes the internal realtime clock.

By evaluating the pseudorandom phase noise, the PZF511 is able to generate time
frames with thousand times the accuracy of standard AM-time code receiver. The precise
regulation of the main oscillator of the radio clock is possible therefore. So, the PZF511
can be used as a standard frequency generator besides the application as a time code
receiver. Four fixed and one settable TTL-level standard frequencies are available at the
rear VG-connector. The synthesizer frequency exists as an open drain output and a
sinewave signal also.

As an addition to the previous PZF510 the PZF511 generates an IRIG timecode that is
available at the rear VG-connector both as a modulated AM and as an unmodulated
DCoutput.

Furthermore the PZF511 provides active-low as well as active-high TTL pulses per
minute and per second. To distribute informations concerning date, time and status, three
independant serial interfaces (RS232) are used which are configurable in a setup menu.

Like mentioned before, the PZF511 includes a battery-backed realtime clock which
runs crystal-precise if the main power supply fails.

Important system parameters are stored in a battery-backed RAM or non-volatile
(EEPROM) memory.

If an update of system software becomes necessary, the new firmware can be loaded
via serial interface (COM0) without removing the PZF511 for inserting a new EPROM.

6

Installation PZF511

To achieve the technical data given in chapter 'technical specifications', the following
points must be observed.

Operating voltage

The clock operates with a single +5V supply. The output voltage should be well
regulated because drifting supply voltages reduce the short time accuracy of the genera­ted frequencies and timing pulses. The power supply lines should have low resistance
and be connected using both pins a and c of the rear connector.

Antenna

The external ferrite antenna AW02 is connected to the receiver by using a 50 ohm coax
cable. If reception is sufficient, the length of the cable can be up to several hundred
meters without any problems. An antenna amplifier is available for very long antenna
cables.

Assembly of antenna

The antenna has to be mounted as exactly as possible. Turning it out of the main receive
direction will result in less accurate time frames. The antenna must be placed in
longitudinal direction to the DCF-transmitter (Frankfurt). The nearness to microcompu­ters should be avoided (PZF511 included) and the antenna should be installed with a
minimum distance of 30cm to all metal objects, if possible. A distance of several meters
to TV- or computermonitors must be kept.

After switching the PZF511 to the menu 'FIELD', the adjustment of the antenna can
be executed. The displayed value is proportional to the received field strength. The best
method of mounting the antenna is to look for the minimum field strength and turn the
antenna by 90° to maximum then. A high field strength on its own is no guarantee for
good conditions of receiption, because interfering signals within the bandwidth of the
receiver also have an effect on the displayed value.

The maximum interference immunity can be found by looking at the autocorrelation
coefficient (in percent) in the menu 'PZF-STAT'. The displayed value should be close to
100% for best receiption.

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Front panel

Pilot lamps

The 'Feld'-LED is switched on if a DCF-signal with at least minimum field strength
needed for the correlation receiption is detected at the input of the receiver.

The 'Syn.'-LED indicates that the autocorrelation coefficient decreases beyond a value
that is needed and a correct receiption is not possible therefore. This happens if a strong
interferer within the bandwidth of the receiver is present or the transmitter is switched of.

If the 'Freil.'-LED is on, it was not possible to synchronize the internal realtime clock
to DCF-time. This condition occures for at most two minutes after switching on the
PZF511, because two DCF-telegrams are checked for plausibility before the data is
taken over. Short disturbance of receiption can cause this state too.

8

Display

The eight digit alphanumeric display shows important information concerning status and
time. The setting of system parameters is also done with the help of the display.

Control keys

It is possible to change the displayed information (time, date or status information) by
two keys. The 'Menu'-key selects one of several menus. After presing the 'Set'-button the
belonging information appears on the display. Furthermore, the keys are used to set user­specific parameters in several submenus.

Menu items

The type of DCF-clock and the software revision are displyed first after power-up. The
following informations are readable before the PZF511 switches to time-display auto­matically:

The handling of any queries will be simplified if the software revision is given by the
user. The following menus are available then:

Menu TIME

In this menu the current time is displayed (this is the default after power up).

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Menu DATE

After the Set button is pressed, the actual date appears on the display.

Menu DAY o.W.

The day of the week will be displayed in this menu.

Menu PZF STAT

Information on the decoding of the pseudo-random sequence is available in this menu.

The following texts may be displayed:

This message indicates that the system tries to achieve a coarse synchronisation. This
procedure starts after power-up or worse receiption for more than ten seconds. If the
coarse synchronisation was successfull, the receiver enters the state of fine-correlation.
The system tries to lock the received PZF as exact as possible to generate a precise time
frame. The display shows the correlation coefficient at the end of each second, which can
be up to 100%. A high value for the coefficient should be achieved by choosing a
suitable position for the antenna.

The essential part of the tracking is completed five seconds after "FC: xx%" appeared
and the generation of pulses per minute and per second starts. Tracking steps of three
microseconds are possible each second until the internal realtime clock is synchronized
(two minutes max.). Afterwards, corrections of the time frame are executed per minute
only. The direction of these steps is displayed by the characters '>' or '<' behind the digits
of the correlation coefficient.

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Menu FIELD

The digitized value of the field strength is displayed in this menu. There is a logarithmic
relation between this value and the field strength. This menu is useful for mounting the
antenna, like described in chapter 'Assembly of antenna'.

Menu SETUP

The user-specific parameters of the PZF511 are set in this menu. To avoid the erroneous
change of these parameters, it is not possible to enter the submenus by a simple pressing
of the Set-button. The first submenu is entered if the Set-button is pressed until the
character '*' is displayed behind the text SETUP and the Menu-key is actuated then.

The following submenus are selectable (Set-button and Menu-key used as usual now):

Menu DIST. o. T

The distance to the transmitter is entered in this menu for compensating the propagation
delay of the received pseudo-random code. This setting should be done as exact as
possible because the absolute precision of the time frame is influenced by this value.

After pressing the Set-button a four digit kilometer-value is displayed. By pressing the
Set-key again, the first position is selected (flashing digit). To choose a different digit, the
Menu-key has to be pressed, to increment the current digit the Set-button must be used. If
the value is entered, it will be stored by pressing the Menu-key until the display returns to
the setup submenu. The km-value is stored in the internal EEPROM of the board.

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