Jackson Labs LC_XO User manual

Revision 08/29/12 B
LC_XO Low Cost Ultra Small 1x1 inch GPSDO Module Spec
0.97 X 0.97 X 0.5 inch Module with
pins
< 1 Min. Crystal Warm Up
50 Channel WAAS GPS Receiver
Very Low Power, TCXO or OCXO
PRELIMINARY SPECIFICATION
TYP. ELECTRICAL SPECIFICATIONS:
Module Specification:
1 PPS Accuracy ±50ns to UTC RMS (1-Sigma) GPS Locked
Holdover Stability <±20us over 3 Hour Period @+25°C (No Motion, OCXO)
1 PPS Output 3.3VDC CMOS
Serial Control SCPI-99 TTL Level, GPS NMEA Output
GPS Frequency L1, C/A 1574MHz
GPS Antenna Active or Passive
GPS Receiver 50 Channels, Mobile, SBAS WAAS, EGNOS, MSAS capable
Sensitivity Acquisition –142 dBm, Tracking -158 dBm
GPS TTFF Cold Start - <45 sec, Warm Start – 1 sec, Hot Start - 1 sec
ADEV 10Ks <5E-012 (OCXO, GPS Locked, 25°C, no motion)
TTL Alarm Output GPS LOCK indicator
Warm Up Time / Stabilization Time <5 min at +25°C to 1E-08 Accuracy
Supply Voltage (Vdd) 3.3V Single-Supply only (5V internally generated and filtered)
Power Consumption 0.7W with OCXO, 0.5W with TCXO
Operating Temperature 0°C to +60°C, -20C to +75C optional
Storage Temperature -45°C to +85°C
Additional Features Firmware field-upgradable, external 1PPS input, status LEDs, compatible
to GPSCon, SNTP, GPSD, and Z38xx software applications, full NMEA
Oscillator Specification (OCXO):
Frequency Output 10MHz CMOS 5Vpp (3.3Vpp optional)
10MHz Retrace ±2E-08 After 1 Hour @ +25°C
Frequency Stability Over Temperature (Unlock Condition) ±2.5E-08 (OCXO) ±7.5E-08 (TCXO)
Output Amplitude 5Vpp CMOS
OCXO Warm Up Time < 1 min @ +25°C
Phase Noise (with 33uF or larger cap on 5V_Output pin 6)
TCXO OCXO
1Hz -65dBc/Hz -75dBc/Hz
10Hz -102dBc/Hz -110dBc/Hz
100Hz -132dBc/Hz -132dBc/Hz
1kHz -148dBc/Hz -142dBc/Hz
10kHz -152dBc/Hz -145dBc/Hz
100KHz <-155dBc/Hz <-150dBc/Hz
Connections: Connector Type:
1PPS Output, 10MHz Output, power, serial communication, system
status, NMEA, 1PPS in, ISP mode enable, antenna input 100 mil spacing on pins, can be soldered, or plugged into a socket, gold- plated pins
Jackson Labs Technologies, Inc., 475 Alberto Way, Suite 120, Los Gatos, CA 95032
Phone: [phone], Fax: [phone], www.jackson-labs.com
[email protected]

Revision 08/29/12 B
LC_XO PINOUT DESCRIPTION:

LC_XO GPSDO User
Manual
Document: 80200517
Version: 1.0
Date: 23 September, 2012

LC_XO GPSDO User Manual
Copyright © 2012 Jackson Labs Technologies, Inc.

© 2012 Jackson Labs Technologies, Inc. i
LC_XO GPSDO User Manual
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 General Safety Precautions . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2.1 Grounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2.2 Power Connections. . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2.3 Environmental Conditions . . . . . . . . . . . . . . . . . . . . . . 2
2 Quick-Start Instructions . . . . . . . . . . . . . . . . . . . . . . 3
2.1 Powering Up the Unit . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1.1 LC_XO Photos . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1.2 LC_XO Mechanical Diagram . . . . . . . . . . . . . . . . . . . . . 5
2.1.3 LC_XO Pinout and Pin Description. . . . . . . . . . . . . . . . . . . 6
2.2 Using a Socket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3 Operating with GPS . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.4 Remote serial control . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.4.1 “Help” and command overview . . . . . . . . . . . . . . . . . . . . 9
2.4.2 Loop parameter adjustment . . . . . . . . . . . . . . . . . . . . . 9
3 Control and Command Utilities . . . . . . . . . . . . . . . . . .11
3.1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
3.2 Z38XX Utility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
3.2.1 Installation and Set Up . . . . . . . . . . . . . . . . . . . . . . .11
3.2.1.1 Parameter Setup . . . . . . . . . . . . . . . . . . . . . .11
3.2.1.2 Serial Echo. . . . . . . . . . . . . . . . . . . . . . . . .12
3.2.1.3 Windows Compatibility . . . . . . . . . . . . . . . . . . . .13
3.2.2 Running the program . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2.2.1 Zoom and Pan . . . . . . . . . . . . . . . . . . . . . . .14
3.2.3 View menu . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
3.2.3.1 Satellite Azimuth/Elevation Chart . . . . . . . . . . . . . . . .15
3.2.3.2 Satellite C/N level Chart. . . . . . . . . . . . . . . . . . . .15
3.2.3.3 Holdover Uncertainty & Sats . . . . . . . . . . . . . . . . . .16
3.2.3.4 Time Stability Measures. . . . . . . . . . . . . . . . . . . .16
3.3 GPScon Utility . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
3.3.1 Installation and Set Up . . . . . . . . . . . . . . . . . . . . . . .18
3.3.1.1 Setting the options . . . . . . . . . . . . . . . . . . . . . .18
3.3.1.2 Communication Parameters . . . . . . . . . . . . . . . . . .18
3.3.1.3 Auxiliary parameters . . . . . . . . . . . . . . . . . . . . .19
3.3.1.4 Other options . . . . . . . . . . . . . . . . . . . . . . . .21
3.3.2 Sending manual commands to the receiver . . . . . . . . . . . . . . .21
3.3.3 Use of the mouse in graph mode . . . . . . . . . . . . . . . . . . .22
3.3.4 Exporting the graphics . . . . . . . . . . . . . . . . . . . . . . .24
3.4 Interpreting the Data . . . . . . . . . . . . . . . . . . . . . . . . . . .25
3.5 Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
4 SCPI-Control Quick Start Instructions . . . . . . . . . . . . . .29
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
4.2 General SCPI Commands . . . . . . . . . . . . . . . . . . . . . . . .29
4.2.1 Quick Start Commands . . . . . . . . . . . . . . . . . . . . . . .29
4.2.2 *IDN? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

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ii © 2012 Jackson Labs Technologies, Inc.
4.2.3 HELP? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.3 GPS Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.3.1 GPS:SATellite . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.3.2 GPS:SATellite:TRAcking:COUNt? . . . . . . . . . . . . . . . . . . 30
4.3.3 GPS:SATellite:VISible:COUNt? . . . . . . . . . . . . . . . . . . . 30
4.3.4 NMEA Support . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.3.5 GPS:GPGGA. . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.3.6 GPS:GGASTat . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.3.7 GPS:GPRMC . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.3.8 GPS:XYZSPeed . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.3.9 GPS:POSition? . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.3.10GPS:RESET ONCE . . . . . . . . . . . . . . . . . . . . . . . . 32
4.3.11GPS?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.4 PTIME Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.4.1 PTIMe:TZONe? . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.4.2 PTIMe:DATE? . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.4.3 PTIMe:TIME? . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.4.4 PTIMe:TIME:STRing? . . . . . . . . . . . . . . . . . . . . . . . 33
4.4.5 PTIMe:TINTerval? . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.4.6 PTIME? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.5 SYNChronization Subsystem . . . . . . . . . . . . . . . . . . . . . . . 33
4.5.1 SYNChronization:SOURce:MODE [GPS|EXTernal|AUTO] . . . . . . . . . 34
4.5.2 SYNChronization:HOLDover:DURation? . . . . . . . . . . . . . . . . 34
4.5.3 SYNChronization:HOLDover:INITiate . . . . . . . . . . . . . . . . . 34
4.5.4 SYNChronization:HOLDover:RECovery:INITiate . . . . . . . . . . . . . 34
4.5.5 SYNChronization:TINTerval? . . . . . . . . . . . . . . . . . . . . 34
4.5.6 SYNChronization:IMMEdiate. . . . . . . . . . . . . . . . . . . . . 34
4.5.7 SYNChronization:FEEstimate? . . . . . . . . . . . . . . . . . . . . 35
4.5.8 SYNChronization:LOCKed? . . . . . . . . . . . . . . . . . . . . . 35
4.5.9 SYNChronization:health? . . . . . . . . . . . . . . . . . . . . . . 35
4.5.10SYNChronization?. . . . . . . . . . . . . . . . . . . . . . . . . 36
4.6 DIAGnostic Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . 36
4.6.1 DIAGnostic:ROSCillator:EFControl:RELative? . . . . . . . . . . . . . . 36
4.6.2 DIAGnostic:ROSCillator:EFControl:ABSolute? . . . . . . . . . . . . . . 36
4.7 MEASURE Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . 36
4.7.1 MEASure:VOLTage?. . . . . . . . . . . . . . . . . . . . . . . . 36
4.7.2 MEASure:CURRent?. . . . . . . . . . . . . . . . . . . . . . . . 36
4.7.3 MEASure? . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
4.8 SYSTEM Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . 37
4.8.1 SYSTem:COMMunicate . . . . . . . . . . . . . . . . . . . . . . 37
4.8.1.1 SYSTem:COMMunicate:SERial:ECHO . . . . . . . . . . . . . 37
4.8.1.2 SYSTem:COMMunicate:SERial:PROmpt . . . . . . . . . . . . 37
4.8.1.3 SYSTem:COMMunicate:SERial:BAUD . . . . . . . . . . . . . 37
4.8.2 SYSTem:STATus? . . . . . . . . . . . . . . . . . . . . . . . . 37
4.8.3 SYSTem:FACToryReset ONCE . . . . . . . . . . . . . . . . . . . 37
4.9 SERVO Subsystem. . . . . . . . . . . . . . . . . . . . . . . . . . . 38
4.9.1 SERVo:COARSeDac . . . . . . . . . . . . . . . . . . . . . . . 38
4.9.2 SERVo:DACGain . . . . . . . . . . . . . . . . . . . . . . . . . 38
4.9.3 SERVo: EFCScale . . . . . . . . . . . . . . . . . . . . . . . . 38
4.9.4 SERVo:EFCDamping . . . . . . . . . . . . . . . . . . . . . . . 38
4.9.5 SERVo:SLOPe . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4.9.6 SERVo:TEMPCOmpensation . . . . . . . . . . . . . . . . . . . . 39

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LC_XO GPSDO User Manual
4.9.7 SERVo:AGINGcompensation . . . . . . . . . . . . . . . . . . . . .39
4.9.8 SERVo:PHASECOrrection . . . . . . . . . . . . . . . . . . . . . .39
4.9.9 SERVo:1PPSoffset . . . . . . . . . . . . . . . . . . . . . . . . .39
4.9.10SERVo:TRACe . . . . . . . . . . . . . . . . . . . . . . . . . .39
4.9.11SERVo? . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
5 Certification and Warranty . . . . . . . . . . . . . . . . . . . . .41
5.1 Certification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
5.1.1 Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
5.1.2 Limitation of Warranty . . . . . . . . . . . . . . . . . . . . . . . .41
5.1.3 Exclusive Remedies . . . . . . . . . . . . . . . . . . . . . . . .42

LC_XO GPSDO User Manual
iv © 2012 Jackson Labs Technologies, Inc.

© 2012 Jackson Labs Technologies, Inc. 1
LC_XO GPSDO User Manual
1Introduction
1.1 Overview
The LC_XO plug-in module generates a highly accurate and stable 10MHz CMOS reference, a
UTC-synchronized 1PPS output, Position, Velocity, Time, and Date using NMEA commands, and
includes an internal 3.3V to 5V DC-DC converter which can provide a clean 5V 0.1A supply to the
customers board. The LC_XO GPSDO includes a high-performance GPS receiver that can acquire
and track up to 50 GPS signals down to a state of the art –158dBm, a 32bit processor that runs a Real
Time OS, a low-noise 5V CMOS 10MHz output, serial control interface and NMEA output,
precision voltage references, and DACs. The unit is built as an easy-to-use plug-in board that can be
soldered into, or plugged into a socket on a customers PCB. All that is required to operate the
LC_XO board is a 3.3V power supply, and a GPS antenna feed. The unit provides an
industry-standard NMEA GPS interface providing Position/Velocity/Timing (PVT) information, as
well as full control/command serial interface using SCPI (GPIB-like) serial commands. The LC_XO
board will use the internal GPS receiver by default to discipline the on-board oscillator, but can also
be configured to auto-switch to, or always lock to an external CMOS/TTL 1PPS reference.
1.2 General Safety Precautions
The following general safety precautions must be observed during all phases of operation of this
instrument. Failure to comply with these precautions or with specific warnings elsewhere in this
manual violates safety standards of design manufacture, and intended use of the instrument. Jackson
Labs Technologies, Inc. assumes no liability for the customer’s failure to comply with these
requirements.
1.2.1 Grounding
To avoid damaging the sensitive electronic components in the LC_XO GPSDO always make sure to
discharge any built-up electrostatic charge to a good ground source, such as power supply ground.
This should be done before handling the circuit board or anything connected to it, i.e. the GPS
antenna.

LC_XO GPSDO User Manual
2© 2012 Jackson Labs Technologies, Inc.
1.2.2 Power Connections
Make sure to connect the DC power to the device following the polarity indicated in Section 2.1 . Do
not reverse the power pins as this will cause serious damage to the circuit board.
1.2.3 Environmental Conditions
This instrument is intended for indoor use. It is designed to operate at a maximum relative
non-condensing humidity of 95% and at altitudes of up to 50,000 meters. Refer to the specifications
tables for the ac mains voltage requirements and ambient operating temperature range.

© 2012 Jackson Labs Technologies, Inc. 3
LC_XO GPSDO User Manual
2Quick-Start
Instructions
2.1 Powering Up the Unit
The unit is powered from an external 3.3V supply on pin 8. The module will present significant
current variations to the external 3.3V power supply during normal operations and it is recommended
that the user bypass pins 8 and 6 with small Tantalum capacitors. The user may use up to 100mA for
external circuitry from the internal low-noise 3.3V to 5V voltage regulator.
The user should provide an L1 antenna signal routed on a microstrip or stripline to pin 10 on the unit.
The antenna can be active or passive, with an amplification range of up to 50dB to compensate for
cable loss. The LC_XO provides 5V with up to 40mA to the antenna and the output is short-circuit
protected.
The unit will start to search for Satellites as soon as power is applied, and will start to lock the
internal OCXO/TCXO to UTC as soon as the 1PPS LED starts blinking with a GPS antenna
attached. After 1 hour or less, the unit should stabilize the frequency, and all event indicators should
be off resulting in the Green LOCK LED to be lit up. At this time the Green LOCK LED will indicate
the unit is fully synchronized to UTC, and generating a stable and accurate 10MHz output signal. The
Green LOCK LED may go off momentarily as airflow touches the unit or Sats come in and out of
view, this is normal behavior.
You may place the GPS antenna in a window, but it is recommended to place the GPS antenna with a
full view of the sky for best performance. The antenna cable can be extended to 10m or more with
high quality antenna cable (use quad shielded RG-6 75 Ohms cable, or high-quality 50 Ohms coax
cable) without significant loss of signal quality.
2.1.1 LC_XO Photos
The LC_XO GPSDO board is shown in :Figure 2.1.

LC_XO GPSDO User Manual
4© 2012 Jackson Labs Technologies, Inc.
Figure 2.1 LC_XO Module Top side
Figure 2.2 LC_XO Module Bottom side

© 2012 Jackson Labs Technologies, Inc. 5
LC_XO GPSDO User Manual
2.1.2 LC_XO Mechanical Diagram
Figure 2.3 LC_XO Pin Locations and Outline Drawing

LC_XO GPSDO User Manual
6© 2012 Jackson Labs Technologies, Inc.
2.1.3 LC_XO Pinout and Pin Description
Figure 2.4 LC_XO Pinout and Pin Description

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LC_XO GPSDO User Manual
Table 2.1 shows the LC_XO board revision 1.0 hardware pin description
Table 2.1 LC_XO board hardware connectors
Pin Name Function
Specification
1 GND GND GND
2 10MHz Out 10MHz output 5V CMOS, <1ns rise time
3 LOCK_OK LOCK
EVENT#
indicator
3.3V: Unit is locked and no
events are pending
0V: Events are pending
4 1PPS OUT 1PPS Output 3.3V CMOS <10ns rise
time
5 1PPS IN 1PPS Input External (optional) 1PPS
Reference Input
6 +5V Out +5V Output 5V +/-5%, <100mA output
from internal DC-DC
switcher. Bypass with
optional 33uF or more for
improved phase noise
7 GND GND GND
8 +3.3Vdd +3.3V Power
Supply
+3.3V, +/-5%, <160mA.
Bypass with optional 10uF
or more for lower noise.
9 GND GND GND
10 ANT IN Antenna Input L1 1574MHz, 5V, 0dB to
50dB antenna gain
11 GND GND GND
12 NMEA Out GPS Raw
NMEA Output
3.3V CMOS, GPS receiver
raw NMEA and
uBlox-binary serial strings
13 ISP# Enable ISP
Mode
Pull to ground during
power-on to enable In
System Flash programming
mode (ISP)

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8© 2012 Jackson Labs Technologies, Inc.
2.2 Using a Socket
The LC_XO board may either be soldered onto a PCB or it can be inserted into a socket on the users’
PCB for optional retrofitting of customer products. The pins used on the LC_XO board are
manufactured by Samtec and have part number BBL-115-G-E. The board may be inserted into a
Samtec mating low profile socket strip of the SL series, or similar products.
2.3 Operating with GPS
Please make sure to connect the GPS antenna prior to connecting power to the unit.
Caution: use a Lightning Arrestor on your Antenna setup.
The LC_XO board GPS receiver includes a 50 channel high-sensitivity GPS receiver with very fast
lock time. It does not require any self-survey or position-hold mode (auto survey), and thus can be
used in mobile platforms.
The LC_XO board is capable of generating standard navigation messages on the SCPI serial port (see
GPS:GPGGA and GPS:GPRMC serial commands) that are compatible with most GPS based
navigation software. Please note that the LC_XO board indicates MSL height (rather than GPS
height) in its GPGGA, GPS? and syst:stat? output strings. The LC_XO also provides raw NMEA and
uBlox binary output strings on pin 12 for additional information.
The internal GPS receiver generates a 1PPS time signal that is phase synchronized to UTC. This
1PPS signal is used to frequency-lock the 10MHz output of the LC_XO board to UTC, thus
disciplining the unit’s 10MHz frequency output to the US Naval master clock for very high
frequency accuracy (typically better than 1ppb of frequency accuracy when locked to GPS). Over the
long term, the LC_XO board will out-perform free-running Cesium Atomic Frequency Standards.
2.4 Remote serial control
• The unit is controlled via the ttl level serial port at 115200 baud, 8N1. Other Baud Rates can be set
via SCPI commands over the serial port.
• WARNING: DO NOT CONNECT THE TTL LEVEL SERIAL PORT TO AN RS-232
LEVEL SERIAL INTERFACE, THIS WILL DAMAGE THE UNIT.
• Attach the LC_XO board to your PC’s Hyperterminal, the Z38xx software available on the
Jackson Labs Technologies, Inc. website, or the optional GPSCon software package. Configure the
application software for 115200 Baud, 8 bits, no parity, 1 stop bit, and no flow control where
applicable.
14 RX In SCPI RX Input 3.3V SCPI serial interface
input, 5V compatible
15 TX Out SCPI/NMEA
Output
3.3V serial output

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LC_XO GPSDO User Manual
2.4.1 “Help” and command overview
• A listing of the available serial commands can be shown by typing "help?" when using TeraTerm
(recommended) or Hyperterm.
• "*IDN?" can be used to see if the connection works. Both commands need to be followed by
pressing “Enter”.
2.4.2 Loop parameter adjustment
• All loop parameters can be controlled via the serial port.
• Loop parameters are optimized for the OCXO/TCXO on the board, and changing the factory
settings may result in the unit’s performance to deteriorate.
The commands to control the loop parameters are part of the servo? command. See also the SERVO
Subsystem section in Chapter 3 (Section 4.9 ).
The individual commands are:
EFC Scale: this is the proportional gain of the PID loop. Higher values will give quicker
convergence, and faster locking of the GPS time (lower loop time constant), lower values give less
noise. Values between 0.7 and 6.0 are typical.
EFC Damping: overall IIR filter time constant. Higher values increase loop time constant. Jackson
Labs Technologies, Inc. typically uses values between 10 to 50. Setting this value too high may cause
loop instability.
Phase compensation: this is the Integral part of the PID loop. This corrects phase offsets between the
LC_XO board 1PPS signal and the UTC 1PPS signal as generated by the GPS receiver. Set higher
values for tighter phase-following at the expense of frequency stability. Typical values range from 4
- 30, 25 being the default. Setting this value too high may cause loop instability.
A well-compensated unit will show performance similar to the plot in Figure 2.5 when experiencing
small perturbations

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10 © 2012 Jackson Labs Technologies, Inc.
Figure 2.5 LC_XO board phase compensation plot

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LC_XO GPSDO User Manual
3Control and Command
Utilities
3.1 Description
The LC_XO board can be connected to a freeware program available on the Jackson Labs
Technologies, Inc. website support page to control and monitor the unit called Z38xx. This program
runs under Windows.
Z38xx can be used to monitor and graphically plot the frequency and phase stability of the unit, the
number of Satellites being tracked, and various other GPS and TCXO performance parameters.
Z38xx needs to be properly configured under the “PARAMETERS” tab prior to operation by setting
up the correct serial parameters (115.2KBaud, 8N1).
Please consult the Z38xx user manual included in the CD ROM for further details.
Alternatively to the Z38xx application, GPSCon is a third-party program for the monitoring and
control of a variety of GPS time and frequency standard receivers. It communicates with the receiver
using the SCPI command set via the USB port. This utility can be obtained directly from Real Ham
Radio.com at the following URL:
http://www.realhamradio.com/gpscon-buy-now.htm
Important note: run Z38xx and GPSCon in Windows XP compatibility mode.
3.2 Z38XX Utility
3.2.1 Installation and Set Up
The Z38XX manual has instructions on how to install and set up the software. All the information
needed to run the program is available in the included user manual. Only some details of setup and
use will be provided here for convenient reference.
3.2.1.1 Parameter Setup
Before communication with Z38XX can take place, the communications parameters must be set. To
do so, click on the Parameters tab. The parameter window will appear as shown in Figure 3.1.

LC_XO GPSDO User Manual
12 © 2012 Jackson Labs Technologies, Inc.
Figure 3.1 Z38XX parameter window
Set the communications parameters as follows:
• Comm port: Windows will assign a comm port. Enter that number in the Com box.
• Baudrate: 115,200
• Data bits: 8 bits
• Stop bits: 1
• Parity: none
3.2.1.2 Serial Echo
For serial communication with Z38XX to work correctly, Serial Echo must be turned off (see the
explanation in the Z38XX manual). To turn off serial echo, click on the Manual Command Entry tab.
The drop-down menu shown in Figure 3.2 will appear. Scroll all the way down and click on
SYST:COMM:SER:ECHO OFF. Wait until the yellow indicator is lit and then press “Send”. This
will send a command to the LC_XO and turn off serial echo.
Note: If you want to run GSPcon utility subsequently, be sure and turn back on Serial
Echo as that program requires it. To do so, click on the Manual Command Entry tab
and scroll down to the menu item SYST:COMM:SER:ECHO ON. Wait until the yellow
indicator is lit and then press ”Send”.