Meinberg GPS162 User Manual

Technical Information

Operating Instructions

GPS162

Incl. Windows Software
GPSMON32

Impressum

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

Telefon: ++49 (0) 52 81 / 9309-0
Telefax: ++49 (0) 52 81 / 9309-30

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

August 17th, 2009

Table of contents

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

Content of the USB stick ..................................................................... 4

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

GPS162 features................................................................................... 6

Block diagram GPS162 .............................................................. 7

Oscillator options ....................................................................... 8

Time zone and daylight saving .................................................. 8

Pulse outputs .............................................................................. 8

Standard frequencies .................................................................. 8

Asynchronous serial ports .......................................................... 9

Enabling of outputs .................................................................... 9

Status outputs ............................................................................. 9

/FAIL output ..................................................................... 9

LOCK output ..................................................................... 9

BSL inputs ................................................................................ 10

Installation ......................................................................................... 10

Power supply ............................................................................ 10

Mounting the antenna ............................................................... 11

Powering up the system ........................................................... 11

Replacing the lithium battery ............................................................ 12

Technical specifications GPS162 ...................................................... 13

Pin assignments of the contact strip ........................................ 15

Board dimensions ..................................................................... 16

Format of the Meinberg standard time string .......................... 17

Format of the SAT time string ................................................. 18

Format of the RACAL standard Time String .......................... 19

Format of the NMEA (RMC) string ........................................ 20

Format of the ABB-SPA timestring ......................................... 21

Format of the time string Uni Erlangen (NTP) ....................... 22

Format of the Computime Time String ................................... 24

Technical specifications of antenna ......................................... 25

Assembly with CN-UB/E (CN-UB-280DC) ............................ 26

The program GPSMON32 ................................................................. 27

Online Help ........................................................................................ 28

Content of the USB stick

Besides this manual, the provided USB stick includes a setup program for the
monitor software GPSMON32. This utility can be used to configure Meinberg GPS
receivers via their serial ports and display status information of the module.

The software is executable under the following operating systems:

- Windows Server 2003

- Windows XP

- Windows 2000

- Windows NT

- Windows ME

- Windows 9x

If the USB stick is lost, the setup program can be downloaded for free at:

http://www.meinberg.de/english/sw/#gpsmon

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General information

The satellite receiver clock GPS162 is designed to provide extremly precise time and
frequency references. The compact size of the board GPS162 allows easy integration
of GPS-controlled timing into synchronization tasks like:

o Synchronization of Telecom networks

o Calibration and synchronization of laboratory equipment

o Synchronization of radio transmitters / base stations

(GSM / CDMA / UMTS / DAB / DVB / TETRA)

The clock has been developed for applications where conventional radio controlled
clocks can´t meet the growing requirements in precision. High precision available 24
hours a day around the whole world is the main feature of the this system which
receives its information from the satellites of the Global Positioning System.

The Global Positioning System (GPS) is a satellite-based radio-positioning, navi­gation, and time-transfer system. It was installed by the United States Departement
of Defense and provides two levels of accuracy: The Standard Positioning Service
(SPS) and the Precise Positioning Service (PPS). While PPS is encrypted and only
available for authorized (military) users, SPS has been made available to the general
public.

GPS is based on accurately measuring the propagation time of signals transmitted
from satellites to the user´s receiver. A nominal constellation of 21 satellites together
with 3 active spares in six orbital planes 20000 km over ground provides a minimum
of four satellites to be in view 24 hours a day at every point of the globe. Four
satellites need to be received simultaneously if both receiver position (x, y, z) and
receiver clock offset from GPS system time must be computed. All the satellites are
monitored by control stations which determine the exact orbit parameters as well as
the clock offset of the satellites´ on-board atomic clocks. These parameters are
uploaded to the satellites and become part of a navigation message which is retrans­mitted by the satellites in order to pass that information to the user´s receiver.

The high precision orbit parameters of a satellite are called ephemeris parameters
whereas a reduced precision subset of the ephemeris parameters is called a satellite´s
almanac. While ephemeris parameters must be evaluated to compute the receiver´s
position and clock offset, almanac parameters are used to check which satellites are
in view from a given receiver position at a given time. Each satellite transmits its
own set of ephemeris parameters and almanac parameters of all existing satellites.

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GPS162 features

The satellite receiver clock GPS162 is as a compact board with dimensions of 80 x
120 mm. The module contains four mounting holes (diameter 3 mm) for easy
integration into the application of the user. The power supply and input/output
signals are available via a 26-pole contact strip. The receiver is connected to the
antenna/converter unit via a BNC-connector by using a 50 Ω-coaxial cable with a
length of up to 300 m. It is possible to connect up to four receivers to one antenna by
using an optional antenna diplexer.

The navigation message coming from the satellites is decoded by GPS162´s
microprocessor. Depending on the oscillator option the GPS system time is tracked
with an accuracy of better than ±250 nsec (TCXO HQ/OCXO LQ) or ±100 nsec
(OCXO MQ/OCXO HQ). Compensation of the RF signal´s propagation delay is done
by automatical determination of the receiver´s position on the globe. A correction
value computed from the satellites´ navigation messages increases the accuracy of
the board´s master oscillator and automatically compensates its aging. The last recent
value is restored from the battery buffered memory at power-up.

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Block diagram GPS162

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Oscillator options

To realize various requirements concerning the accurracy of the frequency outputs,
the module GPS162 may be equipped with different master oscillators. They are
disciplined by the GPS-system for compensation of long term effects like aging and
temperature dependant drift. However, phase locking of the standard frequency to the
pulse per second (PPS) is only available with the oscillator option ‘OCXO MQ’ or
‘OCXO HQ’. The specifications for the different oscillators can be found in chapter
‘Technical specifications GPS162’. A label on the board shows the oscillator

option of the present GPS162.

Time zone and daylight saving

GPS system time differs from the universal time scale (UTC) by the number of leap
seconds which have been inserted into the UTC time scale after GPS has been
initiated in 1980. The current number of leap seconds is part of the navigation
message supplied by the satellites, so GPS162´s internal real time is based on UTC.

Conversion to local time including handling of daylight saving year by year can be
done by the receiver´s microprocessor if the corresponding parameters are set up
with the help of the software GPSMON32 (included Windows software).

Pulse outputs

The pulse generator of the satellite controlled clock GPS162 generates a high- and a
low-active pulse per second (PPS) with a pulse duration of 200msec, which are
available at the contact strip. The turn-on slope of these pulses is phase aligned to
UTC-second.

Standard frequencies

The module GPS162 provides two frequency outputs of 10 MHz which are derived
from the master oscillator of the board. If oscillator option ‘OCXO MQ’ or ‘OCXO
HQ’ was equipped, these standard frequencies are phase locked to the pulse per
second. A TTL- and a sinewave output are available at the contact strip.

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Asynchronous serial ports

Two asynchronous serial interfaces (RS-232) called COM0 and COM1 are available
to the user. Transmission speeds, framings and the kind of the time string can be
configured separately. The serial ports are sending a time string either once per
second, once per minute or on request with ASCII ‘?’ only. Possible time strings are
‘Meinberg Standard’, ‘SAT’, ‘UNI Erlangen (NTP)’, ‘Computime’, ‘ABB-SPA’,
‘Racal’ or ‘NMEA (RMC)’, see the technical specifications for details. Furthermore,
the serial interface COM0 is used for communication with the monitor program. A
possible firmware update is also done via this serial channel.

Enabling of outputs

In the default mode of operation the pulse outputs and the serial interfaces are
disabled until the receiver has synchronized after power-up. However, with the help
of GPSMON32 the system can be configured to enable those outputs immediately
after power-up. This option can be set for each group of signals (pulses and serial
interfaces) seperately.

Status outputs

The satellite receiver clock GPS162 provides two TTL-outputs (/FAIL and LOCK)
for handing-over the status of synchronization of timing and calculation of position
to post-connected systems. These outputs can be used for driving LEDs via an
external resistor (R

= 470 Ω).

min

/FAIL output

The ‘/FAIL’ output switches to TTL high level whenever the internal timing of the
receiver is synchronous to the GPS-system.

LOCK output

The ‘LOCK’ output switches to TTL high level if the receiver has acquired at least
four satellites and has computed its position after power-up. In normal operation the
receiver position is updated continuously as long as at least four satellites can be
received. When the receivers position is known and steady only, a single satellite
needs to be received for synchronization and generatation of output pulses.

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