Meinberg PZF510 User Manual

FUNKUHREN

Technical Information
Operating Instruction

PZF510

Impressum

Werner Meinberg
Auf der Landwehr 22
D-31812 Bad Pyrmont

Phone: ++49 52 81 - 9309-0
Fax: ++49 52 81 - 9309-30

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

January 13, 2005

Table of contents

Impressum ............................................................................................ 2

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

Features PZF510 .................................................................................. 6

Installation ............................................................................................ 7

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

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

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

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

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

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

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

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

TIME:.......................................................................................... 9

DATE: ........................................................................................ 9

DAY o.W. ................................................................................... 9

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

GSYNC........................................................................... 10

K: xx%............................................................................. 10

FIELD....................................................................................... 10

SETUP...................................................................................... 10

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

SYNTH. .......................................................................... 11

SYNTH M. ...................................................................... 11

TIME REF....................................................................... 11

PAR.COM0..................................................................... 11

PAR. COM1 .................................................................... 12

SER.MODE .................................................................... 12

OSZ.ADJ......................................................................... 12

DAC CLR ....................................................................... 12

SER. No. ......................................................................... 12

Asynchronous serial interfaces ........................................................... 13

Pulse outputs....................................................................................... 13

Standard frequencies........................................................................... 13

Frequency synthesizer ........................................................................ 14

DCF77 emulation ............................................................................... 14

Realtime clock .................................................................................... 15

TIME_SYN output............................................................................. 15

Expansion capabilities ........................................................................ 15

Firmware updates ............................................................................... 16

Replacing the lithium battery .............................................................. 16

CE label .............................................................................................. 16

PZF510 with OCXO .......................................................................... 17

Technical specifications ...................................................................... 18

Format of the Meinberg Standard Time String .......................... 21

Signal description PZF510 ................................................................. 22

Pin assignment PZF510 ...................................................................... 23

Structure of menus PZF510 ................................................................ 25

4

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 BCD­coded 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.

5

Features PZF510

The PZF510 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 PZF510 and
synchronizes the internal realtime clock.

By evaluating the pseudorandom phase noise, the PZF510 is able to generate time
frames with thousand times the accuracy of standard AM-time code receiver. The
precise regulation of the main oscillator (TCXO, OCXO optional for higher accuracy)
of the radio clock is possible therefore. So, the PZF510 can be used as a standard
frequency generator besides the application as a time code receiver. Six 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.

The PZF510 delivers TTL-low and TTL-high active pulses per minute and per
second further. To distribute informations concerning date, time and status, two
independant serial interfaces (RS232) are used which are configurable in a setup
menu.

Like mentioned before, the PZF510 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 of the RTC) 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 PZF510 for inserting a new EPROM.

6

Installation

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

Operating voltag e

The clock operates with a single +5V supply. This voltage should be sourced by a
linear regulated power supply. If a switched mode power supply is used, the GND
access of the PZF510 should be grounded directly or via a capacitance of at least 0.1µF.
This connection avoids the signal-to-noise ratio reducing influence of harmonics of the
switched mode power supply.

Antenna

The PZF510 operates with a ferrite antenna which is damped to match the bandwith
needed for the correlation reception.

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 (PZF510 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 PZF510 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 75% for best receiption.

7

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 52%
and 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 PZF510, because two DCF-telegrams are checked for plausibility before the data is
taken over. Short disturbance of receiption can cause this state too.

8