Meinberg GPS170SV User manual

MANUAL
GPS170SV
GPS Receiver Eurocard
4th November 2013
Meinberg Radio Clocks GmbH & Co. KG

Table of Contents
1 Impressum 1
2 General Information GPS 2
3 GPS170SV Features 3
3.1 Time Zone and Daylight Saving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2 PulseandFrequencyOutputs..................................... 3
3.3 TimeCaptureInputs ......................................... 4
3.4 Asynchronous Serial Ports (optional 4x COM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.5 DCF77Emulation........................................... 4
3.6 Programmable pulse (optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.7 TimeCode(optional)......................................... 6
3.7.1 AbstractofTimeCode .................................... 6
3.7.2 BlockDiagramTimeCode .................................. 7
3.7.3 IRIGStandardFormat..................................... 8
3.7.4 AFNORStandardFormat................................... 9
3.7.5 Assignment of CF Segment in IEEE1344 Code . . . . . . . . . . . . . . . . . . . . . . . . 10
3.7.6 GeneratedTimeCodes .................................... 11
3.7.7 Selection of Generated Time Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.7.8 Outputs ............................................ 12
3.7.9 TechnicalData ........................................ 12
4 Installation 13
4.1 TheFrontPanelLayout........................................ 13
4.2 RS232COM0 ............................................. 13
4.3 PowerSupply ............................................. 14
4.4 MountingtheGPSAntenna...................................... 14
4.4.1 Example:............................................ 14
4.4.2 Antenna Short-Circuit Assembly with surge voltage protection . . . . . . . . . . . . . . . 15
4.5 PoweringUptheSystem ....................................... 16
5 Safety Instructions 17
5.1 Skilled/Service-Personnel only: Replacing the Lithium Battery . . . . . . . . . . . . . . . . . . . 17
5.2 CE-Label................................................ 17
6 Technical Specifications GPS170 18
6.1 Oscillatorspecications ........................................ 20
6.2 Technical Specications GPS Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
6.3 TimeStrings.............................................. 22
6.3.1 Format of the Meinberg Standard Time String . . . . . . . . . . . . . . . . . . . . . . . . 22
6.3.2 Format of the Meinberg GPS Time String . . . . . . . . . . . . . . . . . . . . . . . . . . 23
6.3.3 Format of the Meinberg Capture String . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
6.3.4 Format of the SAT Time String . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
6.3.5 Format of the Uni Erlangen String (NTP) . . . . . . . . . . . . . . . . . . . . . . . . . . 26
6.3.6 Format of the NMEA 0183 String (RMC) . . . . . . . . . . . . . . . . . . . . . . . . . . 28
6.3.7 Format of the NMEA 0183 String (GGA) . . . . . . . . . . . . . . . . . . . . . . . . . . 29
6.3.8 Format of the NMEA 0183 String (ZDA) . . . . . . . . . . . . . . . . . . . . . . . . . . 30
6.3.9 Format of the ABB SPA Time String . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
6.3.10 Format of the Computime Time String . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
6.3.11 Format of the RACAL standard Time String . . . . . . . . . . . . . . . . . . . . . . . . . 33
6.3.12 Format of the SYSPLEX-1 Time String . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
6.3.13 Format of the ION Time String . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
6.4 SignalDescriptionGPS170 ...................................... 36
0

Page 0
7 The program GPSMON32 37
7.1 SerialConnection ........................................... 37
7.2 NetworkConnection.......................................... 37
7.3 OnlineHelp .............................................. 37
0 Date: 4th November 2013 GPS170SV

Page 1
1 Impressum
Meinberg Radio Clocks GmbH & Co. KG
Lange Wand 9, 31812 Bad Pyrmont - Germany
Phone: + 49 (0) 52 81 / 93 09 - 0
Fax: + 49 (0) 52 81 / 93 09 - 30
Internet: http://www.meinberg.de
Mail: [e-mail]
Date: 2010-05-20
GPS170SV Date: 4th November 2013 1

Page 2 2 General Information GPS
2 General Information GPS
The satellite receiver clock GPS170 has been designed to provide extremly precise time to its user. 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 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 sys-
tem. 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 24 satellites together with several 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 oset 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 oset 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 oset, 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.
2 Date: 4th November 2013 GPS170SV

Page 3
3 GPS170SV Features
The GPS170SV hardware is a 100mm x 160mm microprocessor board. The 40.6mm wide front panel integrates
two LED indicators and one covered push button. The receiver is connected to the antenna/converter unit by a
50 ohm coaxial cable (refer to "Mounting the Antenna"). Feeding the antenna/converter occurs DC insulated
via the antenna cable. Optional an antenna diplexer for up to four receivers connected to one antenna is available.
The GPS170SV is using the "Standard Positioning Service" SPS. Navigation messages coming in from the satel-
lites are decoded by the GPS170SV microprocessor in order to track the GPS system time. Compensation of
the RF signals propagation delay is done by automatic determination of the receivers geographical position. A
correction value computed from the satellites navigation messages increases the accuracy of the boards oven
controlled master oscillator (OCXO) and automatically compensates the OCXOs aging. The last state of this
value is restored from the battery buered memory at power-up.
The GPS170SV has several dierent optional outputs, including three progammable pulses, modulated / un-
modulated timecode and max. four RS232 COM ports, depending on the hardware conguation. Additionally,
you can get the GPS170SVwith dierent OCXOs (e.g. OCXO- LQ / MQ / HQ / DHQ or Rubidium) to cover
all levels of accuracy requirements.
You can review and change the hard- and software conguration options of the clock with the GPSMON32
application(see corresponding section in this manual).
3.1 Time Zone and Daylight Saving
GPS system time diers from the universal time scale (UTC) by the number of leap seconds which have been
inserted into the UTC time scale since GPS was initiated in 1980. The current number of leap seconds is part of
the navigation message supplied by the satellites, so the internal real time of the GPS170 is based on UTC time
scale. Conversion to local time and annual daylight saving time can be done by the receiver's microprocessor if
the corresponding parameters are set up by the user.
3.2 Pulse and Frequency Outputs
The pulse generator of GPS170 generates pulses once per second (P_SEC) and once per minute (P_MIN).
Additionally, master frequencies of 10 MHz, 1 MHz and 100 kHz are derived from the OCXO. All the pulses are
available with TTL level at the rear connector.
Frequency Outputs (optional)
The included synthesizer generates a frequency from 1/8 Hz up to 10 MHz synchronous to the internal timing
frame. The phase of this output can be shifted from -360
◦
to +360
◦
for frequencies less than 10 kHz. Both
frequency and phase can be setup from the front panel or using the serial port COM0. Synthesizer output is
available at the rear connector as sine-wave output (F_SYNTH_SIN), with TTL level (F_SYNTH) and via an
open drain output (F_SYNTH_OD). The open drain output can be used to drive an optocoupler when a low
frequency is generated.
In the default mode of operation, pulse outputs and the synthesizer output are disabled until the receiver has
synchronized after power-up. However, the system can be congured to enable those outputs immediately after
power-up. An additional TTL output (TIME_SYN) reects the state of synchronization. This output switches
to TTL HIGH level when synchronization has been achieved and returns to TTL LOW level if not a single satellite
can be received or the receiver is forced to another mode of operation by the user.
GPS170SV Date: 4th November 2013 3

Page 4 3 GPS170SV Features
3.3 Time Capture Inputs
Two time capture inputs called User Capture 0 and 1 are provided at the rear connector (CAP0 and CAP1) to
measure asynchronous time events. A falling TTL slope at one of these inputs lets the microprocessor save the
current real time in its capture buer. From the buer, capture events are transmitted via COM0 or COM1 and
displayed on LCD. The capture buer can hold more than 500 events, so either a burst of events with intervals
down to less than 1.5 msec can be recorded or a continuous stream of events at a lower rate depending on the
transmission speed of COM0 or COM1 can be measured.
The format of the output string is ASCII, see the technical specications at the end of this document for details.
If the capture buer is full a message "** capture buer full" is transmitted, if the interval between two captures
is too short the warning "** capture overrun" is being sent.
3.4 Asynchronous Serial Ports (optional 4x COM)
Four asynchronous serial RS232 interfaces (COM0 ... COM3) are available to the user. In the default mode
of operation, the serial outputs are disabled until the receiver has synchronized after power-up. However, the
system can be congured to enable those outputs immediately after power-up. Transmission speeds, framings
and mode of operation can be congured separately using the setup menu. COM0 is compatible with other radio
remote clocks made by Meinberg. It sends the time string either once per second, once per minute or on request
with ASCII ? only. Also the interfaces can be congured to transmit capture data either automatically when
available or on request. The format of the output strings is ASCII, see the technical specications at the end
of this document for details. A separate document with programming instructions can be requested dening a
binary data format which can be used to exchange parameters with GPS170 via COM0.
3.5 DCF77 Emulation
The satellite controlled clock generates TTL level time marks (active HIGH) which are compatible with the time
marks spread by the German long wave transmitter DCF77. This long wave transmitter installed in Mainingen
near Frankfurt/Germany transmits the reference time of the Federal Republic of Germany: time of day, date
of month and day of week in BCD coded second pulses. Once every minute the complete time information is
transmitted. However, the generates time marks representing its local time as congured by the user, including
announcement of changes in daylight saving and announcement of leap seconds. The coding sheme is given
below:
M Start of Minute (0.1 s)
R RF Transmission via secondary antenna
A1 Announcement of a change in daylight saving
Z1, Z2 Time zone identification
Z1, Z2 = 0, 1: Daylight saving disabled
Z1, Z2 = 1, 0: Daylight saving enabled
A2 Announcement of a leap second
S Start of time code information
P1, P2, P3 Even parity bits
0
10
20
30
40
50
R
M
1
4
2
1
20
10
8
4
2
1
P2
02
01
8
4
2
1
2
4
8
10
1
2
4
8
10
20
40
80
3
P
A1
Z1
Z2
A2
S
1
2
4
8
10
20
40
1P
Minute
(reserved)
Hour
Day of Month
Day of Week
Year of the Century
Month of Year
Time marks start at the beginning of new second. If a binary "0" is to be transmitted, the length of the
corresponding time mark is 100 msec, if a binary "1" is transmitted, the time mark has a length of 200 msec.
The information on the current date and time as well as some parity and status bits can be decoded from the
time marks of the 15th up to the 58th second every minute. The absence of any time mark at the 59th second
of a minute signals that a new minute will begin with the next time mark. The DCF emulation output is enabled
immediately after power-up.
4 Date: 4th November 2013 GPS170SV

3.6 Programmable pulse (optional) Page 5
3.6 Programmable pulse (optional)
At the male connector Typ VG64 there are three programmable TTL outputs (Prog Pulse 0-2), which are arbi-
trarily programmable.
Other technical details are described at the end of this manual.
GPS170SV Date: 4th November 2013 5

Page 6 3 GPS170SV Features
3.7 Time Code (optional)
3.7.1 Abstract of Time Code
The transmission of coded timing signals began to take on widespread importance in the early 1950s. Especially
the US missile and space programs were the forces behind the development of these time codes, which were used
for the correlation of data. The denition of time code formats was completely arbitrary and left to the individual
ideas of each design engineer. Hundreds of dierent time codes were formed, some of which were standardized
by the "Inter Range Instrumentation Group" (IRIG) in the early 60s.
Except these "IRIG Time Codes", other formats like NASA36, XR3 or 2137 are still in use. The board GPS170
however generates the IRIG-B, AFNOR NFS 87-500 code as well as IEEE1344 code which is an IRIG-B123 coded
extended by information for time zone, leap second and date. Other formats may be available on request.
A modulated IRIG-B (3Vpp into 50W) and an unmodulated DC level shift IRIG-B (TTL) signal are available
at the VG64 male connector of the module.
6 Date: 4th November 2013 GPS170SV

3.7 Time Code (optional) Page 7
3.7.2 Block Diagram Time Code
modulated time code modulated time code hgh active and low active
driver
50 Ω unbalanced
driver
TTL
D/A converter
modulator
digital
sinewave
generator
microcontroller
time code
EPLD
10 MHz
PPS
GPS170SV Date: 4th November 2013 7

Page 8 3 GPS170SV Features
3.7.3 IRIG Standard Format
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3.7 Time Code (optional) Page 9
3.7.4 AFNOR Standard Format
GPS170SV Date: 4th November 2013 9

Page 10 3 GPS170SV Features
3.7.5 Assignment of CF Segment in IEEE1344 Code
Bit No. Designation Description
49 Position Identier P5
50 Year BCD encoded 1
51 Year BCD encoded 2 low nibble of BCD encoded year
52 Year BCD encoded 4
53 Year BCD encoded 8
54 empty, always zero
55 Year BCD encoded 10
56 Year BCD encoded 20 high nibble of BCD encoded year
57 Year BCD encoded 40
58 Year BCD encoded 80
59 Position Identier P6
60 LSP - Leap Second Pending set up to 59s before LS insertion
61 LS - Leap Second 0 = add leap second, 1 = delete leap second 1.)
62 DSP - Daylight Saving Pending set up to 59s before daylight saving changeover
63 DST - Daylight Saving Time set during daylight saving time
64 Timezone Oset Sign sign of TZ oset 0 = '+', 1 = '-'
65 TZ Oset binary encoded 1
66 TZ Oset binary encoded 2 Oset from IRIG time to UTC time.
67 TZ Oset binary encoded 4 Encoded IRIG time plus TZ Oset equals UTC at all times!
68 TZ Oset binary encoded 8
69 Position Identier P7
70 TZ Oset 0.5 hour set if additional half hour oset
71 TFOM Time gure of merit
72 TFOM Time gure of merit time gure of merit represents approximated clock error. 2.)
73 TFOM Time gure of merit 0x00 = clock locked, 0x0F = clock failed
74 TFOM Time gure of merit
75 PARITY parity on all preceding bits incl. IRIG-B time
1.) current rmware does not support leap deletion of leap seconds
2.) TFOM is cleared, when clock is synchronized rst after power up. see chapter Selection of generated timecode
10 Date: 4th November 2013 GPS170SV

3.7 Time Code (optional) Page 11
3.7.6 Generated Time Codes
The internal time code generator may be congured to produce various pulse width modulated IRIG-B or AFNOR
signals. Codes can be output via the front panel bre optic ports FO1. . . FO3.
a) B002: 100 pps, DCLS signal, no carrier
BCD time-of-year
b) B003: 100 pps, DCLS signal, no carrier
BCD time-of-year, SBS time-of-day
c) B006: 100 pps, DCLS Signal, no carrier
BCD time-of-year, Year
d) B007: 100 pps, DCLS Signal, no carrier
BCD time-of-year, Year, SBS time-of-day
e) AFNOR : Code according to NFS-87500, 100 pps, wave signal,
1kHz carrier frequency, BCD time-of-year, complete date,
SBS time-of-day, Signal level according to NFS-87500
f) IEEE1344: Code according to IEEE1344-1995, 100 pps, AM sine wave signal,
1kHz carrier frequency, BCD time-of-year, SBS time-of-day,
IEEE1344 extensions for date, timezone, daylight saving and
leap second in control functions (CF) segment.
(also see table 'Assignment of CF segment in IEEE1344 mode')
g) C37.118: C37.118(DC) Code acc. C37.118, 100 pps, no carrier, BCD time-of-year,
SBS time-of-day,C37.118 extensions for date, timezone, daylight
saving and leap second in control functions (CF) segment
( also see table `Assignment of CF segment in IEEE1344 mode' but
sign bit of local oset is inverted )
GPS170SV Date: 4th November 2013 11

Page 12 3 GPS170SV Features
3.7.7 Selection of Generated Time Code
The time code to be generated can be selected by Menu Setup IRIG-settings or the GPS Monitorprogram
GPSMON32 (except Lantime models). DC-Level Shift Codes (PWM-signal) B00x and modulated sine wave
carrier B12x are always generated simultaneously. Both signals are provided at the VG64-Connector, i.e. if code
B132 is selected also code B002 is available. This applies for the codes AFNOR NFS 87-500 and IEEE1344 as well.
The TFOM eld in IEEE1344 code is set dependent on the 'already sync'ed' character ('#') which is sent
in the serial time telegram. This character is set, whenever the preconnected clock was not able to synchronize
after power up reset. The 'time gure of merit' (TFOM) eld is set as follows.
Clock synchronized once after power up: TFOM = 0000
Clock not synchronized after power up: TFOM = 1111
For testing purposes the output of TFOM in IEEE1344 mode can be disabled. The segment is set to all zeros
then.
3.7.8 Outputs
The module GPS170 provides modulated (AM) and unmodulated (DCLS) outputs. The format of the timecodes
is illustrated in the diagramms "IRIG-" and "AFNOR standard-format".
AM - Sine Wave Output
The amplitude-modulated carrier is available at the VG-connector pin 14a. The carrier frequency depends on
the code and has a value of 1 kHz (IRIG-B). The signal amplitude is 3 Vpp (MARK) and 1 Vpp (SPACE) into
50 Ohm. The encoding is made by the number of MARK-amplitudes during ten carrier waves. The following
agreements are valid:
a) binary "0": 2 MARK-amplitudes, 8 SPACE-amplitudes
b) binary "1": 5 MARK-amplitudes, 5 SPACE-amplitudes
c) position-identier: 8 MARK-amplitudes, 2 SPACE-amplitudes
DCLS Output
The pulse width DCLS signals shown in the diagramms "IRIG" and "AFNOR standard format" are coexistent to
the modulated output and is available at the VG connector pin 13a with TTL level.
3.7.9 Technical Data
OUTPUTS: Unbalanced AM-sine wave-signal:
3 VPP (MARK) / 1 VPP (SPACE) into 50 Ohm
DCLS signal: TTL
12 Date: 4th November 2013 GPS170SV

Page 13
4 Installation
4.1 The Front Panel Layout
FAIL LED
The FAIL LED is turned on whenever the TIME_SYN
output is low (receiver is not synchronized).
LOCK LED
The LOCK LED is turned on when after power-up the
receiver has acquired at least four satellites and has
computed its position. 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 to synchronize and generate output pulses.
BSL Button
Whenever the on-board software must be upgraded or
modied, the new rmware can be downloaded to the
internal ash memory via the serial port COM0. There
is no need to open the metal case and insert a new
EPROM.
If the BSL pushbutton behind the front panel is pressed while the system is powered up, a bootstrap-loader is
actived and waits for instructions from the serial port COM0. The new rmware can be sent to GPS170SV from
any standard PC with serial interface. A loader program will be shipped together with the le containing the
image of the new rmware.
The contents of the program memory will not be modied until the loader program has sent the command
to erase the ash memory. So if the BSL pushbutton is pressed unintentionally while the system is powered up,
the rmware will not be changed accidentially. After the next power-up, the system will be ready to operate
again.
4.2 RS232 COM0
3
5
2
RS232
COM0
GND
TxD0
RxD0
The serial port COM0 is accessible via a 9pin DSUB
male connector (older version 9pol. DSUB male con-
nector) in the frontpanel of the GPS170, parallel hard-
wired to the COM0 port on the rear VG edge connector.
GPS170SV Date: 4th November 2013 13

Page 14 4 Installation
4.3 Power Supply
The power supply used with a GPS170 has to provide only one output of +5V. 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 must be connected using both pins a and
c of the rear connector.
4.4 Mounting the GPS Antenna
The GPS satellites are not stationary but circle round the globe in a period of about 12 hours. They can only be
received if no building is in the line-of-sight from the antenna to the satellite, so the antenna/converter unit must
be installed in a location from which as much of the sky as possible can be seen. The best reception is given
when the antenna has a free view of 8
◦
angular elevation above horizon. If this is not possible the antenna should
be installed with a mostly free view to the equator because of the satellite courses which are located between
latitudes of 55
◦
North and 55
◦
South. If even this is not possible problems occure especially when at least four
sattelites for positioning have to be found.
The antenna/converter unit can be mounted on a pole with a diameter up to 60 mm or at a wall. A 45
cm plastic tube, two holders for wall-mounting and clamps for pole-mounting are added to every GPS170. A
standard coaxial cable with 50 ohm impedance should be used to connect the antenna/converter unit to the
receiver. The maximum lenght of cable between antenna and receiver depends on the attenuation factor of the
used coaxial cable.
Up to four GPS170 receivers can be run with one antenna/converter unit by using the optional antenna diplexer.
The total length of one antenna line between antenna, diplexer and receiver must not be longer than the max.
lenght shown in the table above. The position of the diplexer in the antenna line does not matter.
High voltage protectors must be installed directly after reaching the indoors. The optional delivered protec-
tion kit is not for outdoor usage.
Note:
If the antenna cable was assembled by the user: before powering up the system, make sure that there is no
short-circuit between the inner and outer conductor of the antenna cable, because this could cause a fault of
GPS170.
4.4.1 Example:
Type of cable diameter Ø Attenuation at 100MHz max lenght.
[mm] [dB]/100m [m]
RG58/CU 5mm 17 300 (1)
RG213 10.5mm 7 700 (1)
(1)This specications are made for antenna/converter units produced after January, 2005
The values are typically ones; the exact ones are to nd out from the data sheet of the used cable
14 Date: 4th November 2013 GPS170SV

4.4 Mounting the GPS Antenna Page 15
4.4.2 Antenna Short-Circuit Assembly with surge voltage protection
Optional a surge voltage protector for coaxial lines is available. The shield has to be connected to earth as short
as possible by using the included mounting bracket. Normally you connect the antenna converter directly with
the antenna cable to the system.
GPS170SV Date: 4th November 2013 15

Page 16 4 Installation
4.5 Powering Up the System
If both the antenna and the power supply have been connected the system is ready to operate. About 10 seconds
after power-up the receivers (OCXO-LQ) until 3 minutes (OCXO-MQ / HQ) has warmed up and operates with
the required accuracy. If the receiver nds valid almanac and ephemeris data in its battery buered memory and
the receivers position has not changed signicantly since its last operation the receiver can nd out which satel-
lites are in view now. Only a single satellite needs to be received to synchronize and generate output pulses, so
synchronization can be achieved maximally one minute after power-up (OCXO-LQ) until 10 minutes (OCXO-MQ
/ HQ) . After 20 minutes of operation the OCXO is full adjusted and the generated frequencies are within the
spezied tolerances.
If the receiver position has changed by some hundred kilometers since last operation, the satellites real ele-
vation and doppler might not match those values expected by the receiver thus forcing the receiver to start
scanning for satellites. This mode is called Warm Boot because the receiver can obtain ID numbers of existing
satellites from the valid almanac. When the receiver has found four satellites in view it can update its new position
and switch to Normal Operation. If the almanac has been lost because the battery had been disconnected the
receiver has to scan for a satellite and read in the current almanacs. This mode is called Cold Boot. It takes
12 minutes until the new almanac is complete and the system switches to Warm Boot mode scanning for other
satellites.
In the default mode of operation, neither pulse and synthesizer outputs nor the serial ports will be enabled
after power-up until synchronization has been achieved. However, it is possible to congure some or all of those
outputs to be enabled immediately after power-up. If the system starts up in a new environment (e. g. receiver
position has changed or new power supply) it can take some minutes until the OCXOs output frequency has
been adjusted. Up to that time accuracy of frequency drops to 10-8 reducing the accuracy of pulses to +-5 µ s.
16 Date: 4th November 2013 GPS170SV