Spectracom 8183A NETCLOCK, 8183A GTP Instruction Manual

MODEL 8183A NETCLOCK/GTP

GPS MASTER CLOCK

INSTRUCTION MANUAL

SPECTRACOM CORPORATION

95 Methodist Hill Drive

Suite 500

Rochester, NY 14623

PHONE [phone]
FAX [phone]

www.spectracomcorp.com

Copyright  2003 Spectracom Corporation. All rights reserved.
Contents of this publication may not be reproduced in any form
without the written permission of Spectracom Corporation.

REVISIONS, IF ANY, ARE LOCATED AT THE END OF THE MANUAL

MANUAL REVISION 1.2

July 2003

5-Year Warranty

LIMITED WARRANTY________________________________

Spectracom warrants each new product manufactured and sold by
it to be free from defects in material, workmanship, and
construction, except for batteries, fuses, or other material normally
consumed in operation that may be contained therein, for five
years after shipment to the original purchaser (which period is
referred to as the "warranty period"). This warranty shall not
apply if the product is used contrary to the instructions in its
manual or is otherwise subjected to misuse, abnormal operations,
accident, lightning or transient surge, repairs or modifications not
performed by Spectracom.

The GPS receiver is warranted for one year from date of shipment
and subject to the exceptions listed above. The power adaptor, if
supplied, is warranted for one year from date of shipment and
subject to the exceptions listed above.

The Rubidium oscillator, if supplied, is warranted for two years
from date of shipment and subject to the exceptions listed above.

All other items and pieces of equipment not specified above,
including the antenna unit, antenna surge suppressor and antenna
pre-amplifier are warranted for 5 years, subject to the exceptions
listed above.

WARRANTY CLAIMS________________________________

Spectracom's obligation under this warranty is limited to in-factory
service and repair, at Spectracom's option, of the product or the
component thereof, which is found to be defective. If in
Spectracom's judgment the defective condition in a Spectracom
product is for a cause listed above for which Spectracom is not
responsible, Spectracom will make the repairs or replacement of
components and charge its then current price, which buyer agrees
to pay.

Spectracom shall not have any warranty obligations if the
procedure for warranty claims is not followed. Users must notify
Spectracom of the claim with full information as to the claimed
defect. Spectracom products shall not be returned unless a return
authorization number is issued by Spectracom. Spectracom
products must be returned with the description of the claimed
defect and identification of the individual to be contacted if
additional information is needed. Spectracom products must be
returned properly packed with transportation charges prepaid.

EXCEPT FOR THE LIMITED WARRANTY STATED ABOVE,
SPECTRACOM DISCLAIMS ALL WARRANTIES OF ANY KIND
WITH REGARD TO SPECTRACOM PRODUCTS OR OTHER
MATERIALS PROVIDED BY SPECTRACOM, INCLUDING
WITHOUT LIMITATION ANY IMPLIED WARRANTY OR
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Spectracom shall have no liability or responsibility to the original
customer or any other party with respect to any liability, loss, or
damage caused directly or indirectly by an Spectracom product,
material, or software sold or provided by Spectracom,
replacement parts or units, or services provided, including but not
limited to any interruption of service, excess charges resulting from
malfunctions of hardware or software, loss of business or
anticipatory profits resulting from the use or operation of the
Spectracom product or software, whatsoever or howsoever
caused. In no event shall Spectracom be liable for any direct,
indirect, special or consequential damages whether the claims are
grounded in contract, tort (including negligence), or strict liability.

EXTENDED WARRANTY COVERAGE___________________

Extended warranties can be purchased for additional periods
beyond the standard five-year warranty. Contact Spectracom no
later than the last year of the standard five-year warranty for
extended coverage.

SPECTRACOM 95 Methodist Hill Drive ROCHESTER NY 14623 USA

+1.585.321.5800 FAX: [phone] www.spectracomcorp.com [e-mail]

TABLE OF CONTENTS

SECTION 1 GENERAL INFORMATION

1.0 INTRODUCTION...................................................................................................................1-1

1.1 FEATURES ...........................................................................................................................1-2

1.2 WARRANTY INFORMATION AND PRODUCT SUPPORT ................................................. 1-2

1.3 MANUAL ERRATA AND SPECIAL DOCUMENTATION .....................................................1-3

1.4 UNPACKING.........................................................................................................................1-3

1.5 SPECIFICATIONS ................................................................................................................1-4

1.5.1 Receiver 1-4

1.5.2 Display 1-4

1.5.3 Status Indicators 1-4

1.5.4 RS-232 Serial Comm 1-5

1.5.5 RS-485 Remote Output 1-5

1.5.6 FAA IRIG B Outputs 1-6

1.5.7 1PPS Output 1-6

1.5.8 Standard 10 MHz Output 1-7

1.5.9 Input Power 1-7

1.5.10 Mechanical and Environmental 1-7

1.5.11 Model 8225 GPS Antenna Specifications 1-7

1.5.11.1 Electrical Specifications 1-7

1.5.11.2 Mechanical Specifications 1-8

1.5.12 Model 8226 Impulse Suppressor 1-8

1.5.13 Model 8227 Inline Amplifier 1-8

1.5.14 MP10-0000-0001 Grounding Panel 1-8

1.5.15 CA07xxx GPS Antenna Cable 1-8

SECTION 2 INSTALLATION

2.0 INTRODUCTION................................................................................................................... 2-1

2.1 MODEL 8225 GPS ANTENNA ............................................................................................. 2-1

2.1.1 Antenna Installation 2-1

2.2 ANTENNA CABLE ................................................................................................................ 2-2

2.2.1 Cable Lengths 2-3

2.3 MODEL 8226 IMPULSE SUPPRESSOR .............................................................................2-3

2.4 MP10-0000-0001 COPPER GROUNDING PANEL ............................................................. 2-5

2.5 MODEL 8227 GPS INLINE AMPLIFIER............................................................................... 2-6

2.6 NETCLOCK/GPS PREPARATION FOR USE...................................................................... 2-7

2.6.1 Antenna Connection 2-7

2.6.2 Power Connection 2-7

2.6.3 Chassis Ground 2-8

2.6.4 Configuration 2-8

2.7 INITIAL OPERATION............................................................................................................ 2-12

2.8 QUALIFYING THE INSTALLATION .....................................................................................2-13

2.8.1 GPS Signal Status 2-13

2.8.2 Tracking Histogram 2-13

SECTION 3 OPERATION

3.0 INTRODUCTION................................................................................................................... 3-1

3.1 FRONT PANEL FUNCTIONS .............................................................................................. 3-1

3.1.1 Display 3-1

3.1.2 GPS Lock Lamp 3-1

3.1.3 Time Sync Lamp 3-2

3.2 REAR PANEL FUNCTIONS ................................................................................................. 3-3

3.2.1 GPS Antenna 3-3

3.2.2 Standard 10 MHz Output 3-3

3.2.3 1PPS Output 3-3

3.2.4 FAA IRIG B Outputs 3-4

3.2.5 RS-232 Serial Communication Ports 3-5

3.2.6 Remote Outputs 3-6

3.2.7 Serial Setup Interface 3-7

3.2.8 Status Messages 3-8

3.2.9 DC Power 3-10

3.2.10 Chassis Ground 3-10

3.3 DATA FORMAT DESCRIPTION .......................................................................................... 3-10

3.3.1 Format 0 3-11

3.3.2 Format 1 3-13

3.3.3 Format 2 3-14

3.3.4 Format 3 3-16

3.3.5 Format 4 3-18

3.3.6 Format 90 3-19

3.4 REMOTE OUTPUT USAGE ................................................................................................. 3-21

3.4.1 RS-485 Guidelines 3-21

3.4.2 Connection Method 3-22

3.4.3 Termination 3-30

SECTION 4 SOFTWARE COMMANDS

4.0 INTRODUCTION................................................................................................................... 4-1

4.1 ANTENNA CABLE DELAY ................................................................................................... 4-3

4.2 DISPLAY OUTPUT CONFIGURATION................................................................................ 4-4

4.3 DISPLAY ALARM LOG......................................................................................................... 4-5

4.4 DATE..................................................................................................................................... 4-6

4.5 RESTORE FACTORY DEFAULTS....................................................................................... 4-7

4.6 DISPLAY TRACKING HISTOGRAM .................................................................................... 4-8

4.7 DAYLIGHT SAVING TIME.................................................................................................... 4-10

4.8 FRONT PANEL FORMAT..................................................................................................... 4-13

4.9 GPS SIGNAL STRENGTH ................................................................................................... 4-15

4.10 HELP DISPLAY..................................................................................................................... 4-18

4.11 IRIG CONFIGURATION ....................................................................................................... 4-19

4.12 LOCATION............................................................................................................................ 4-20

4.13 GPS LOCK TIME OUT.......................................................................................................... 4-21

4.14 REMOTE OUTPUT CONFIGURATION ............................................................................... 4-22

4.15 RESET GPS RECEIVER ...................................................................................................... 4-23

4.16 SERIAL COMM CONFIGURATION...................................................................................... 4-24

4.17 SET MODE ........................................................................................................................... 4-26

4.18 STATUS COMMAND............................................................................................................ 4-27

4.19 SYNC TIME OUT .................................................................................................................. 4-28

4.20 TIME...................................................................................................................................... 4-29

4.21 TEST MODE ......................................................................................................................... 4-30

4.22 VERSION COMMAND.......................................................................................................... 4-31

SECTION 5 SERVICE INFORMATION

5.0 INTRODUCTION................................................................................................................... 5-1

5.1 RECEPTION TROUBLESHOOTING.................................................................................... 5-1

5.1.1 No Reception 5-1

5.1.2 Low GPS Quality 5-2

5.2 OSCILLATOR ADJUSTMENT .............................................................................................. 5-4

5.2.1 Adjustment Procedure 5-4

APPENDIX A FAA IRIG CODE DESCRIPTION

A.0 INTRODUCTION................................................................................................................... A-1

A.1 MODEL 8228 GPS ANTENNA ............................................................................................. A-1

A.1.1 FAA IRIG B General Description A-1

ILLUSTRATIONS

FIGURE 1-1 NETCLOCK/GPS MASTER CLOCK 1-1

FIGURE 2-1 ANTENNA INSTALLATION 2-2
FIGURE 2-2 MODEL 8226 IMPULSE SUPPRESSOR 2-3
FIGURE 2-3 CONNECTOR ASSEMBLY INSTRUCTIONS 2-4
FIGURE 2-4 GROUNDING PLATE INSTALLATION 2-5
FIGURE 2-5 MODEL 8227 GPS INLINE AMPLIFIER 2-6
FIGURE 2-6 CABLE GUIDELINES 2-7

FIGURE 3-1 NETCLOCK/GPS FRONT PANEL 3-2
FIGURE 3-2 NETCLOCK/GPS REAR PANEL 3-3
FIGURE 3-3 IRIG CONNECTOR 3-4
FIGURE 3-4 SERIAL COMM PIN NUMBERING 3-5
FIGURE 3-5 REMOTE OUTPUTS 3-6
FIGURE 3-6 RS-485 OUTPUT 3-7
FIGURE 3-7 PIN NUMBERING 3-7
FIGURE 3-8 ONE-WAY BUS INSTALLATION 3-22
FIGURE 3-9 SPLIT BUS CONFIGURATION 3-23
FIGURE 3-10 WIRE STRAIN RELIEF 3-24
FIGURE 3-11 TIMEVIEW RS-485 INTERFACE 3-25
FIGURE 3-12 MODEL 8179T TIMETAP RS-485 INTERFACE 3-25
FIGURE 3-13 MODEL 8188 RS-485 INTERFACE 3-26
FIGURE 3-14 TIMETALK RS-485 INTERFACE 3-26
FIGURE 3-15 TIMEBURST RS-485 INTERFACE 3-27

FIGURE 4-1 COMMAND STRUCTURE 4-1
FIGURE 4-2 TIME DIFFERENCE MAP 4-14

FIGURE A-1 FAA IRIG B TIME CODE A-1

TABLES

TABLE 1-1 MODEL 8183 ANCILLARY KIT 1-3

TABLE 3-1 IRIG PIN OUT 3-4
TABLE 3-2 SERIAL COMM PIN ASSIGNMENTS 3-5
TABLE 3-3 PIN ASSIGNMENTS 3-8
TABLE 3-4 QUALITY INDICATORS 3-15
TABLE 3-5 CABLE SOURCES FOR RS-485 LINES OVER 1500 FEET 3-21
TABLE 3-6 CABLE SOURCES FOR RS-485 LINES UNDER 1500 FEET 3-22

TABLE 4-1 ALPHABETICAL LIST OF COMMANDS 4-2

TABLE 5-1 TYPICAL ANTENNA CABLE RESISTANCE VALUES 5-1
TABLE 5-2 TELEVISION STATIONS WITH GPS JAMMING POTENTIAL 5-3
TABLE 5-3 FM RADIO FREQUENCIES WITH GPS JAMMING POTENTIAL 5-3

TABLE A-1 FAA TIME ERROR INDICATORS A-4

Illustrations road map

FIGURE 1-1 NETCLOCK/GPS MASTER CLOCK
FIGURE 2-1 ANTENNA INSTALLATION 8226_b.eps
FIGURE 2-2 CABLE CLAMP INSTALLATION Net-pc.cgm

FIGURE 3-1 NETCLOCK/GPS FRONT PANEL Net-fr.cgm
FIGURE 3-2 NETCLOCK/GPS REAR PANEL Net-bk.cgm
FIGURE 3-3 SERIAL COMM PIN NUMBERING Femdin.pcx
FIGURE 3-4 REMOTE OUTPUTS Remotout.cgm
FIGURE 3-5 RS-485 OUTPUT Resides in document
FIGURE 3-6 PIN NUMBERING Femdin.pcx
FIGURE 3-7 TIMER RELAY CONTACTS Resides in document
FIGURE 3-8 ALARM RELAY CONTACTS Resides in document
FIGURE 3-9 ONE-WAY BUS INSTALLATION 1way.wmf
FIGURE 3-10 SPLIT BUS CONFIGURATION Splitbus.wmf
FIGURE 3-11 TIMEVIEW RS-485 INTERFACE 81838177.pcx
FIGURE 3-12 MODULAR JACK INTERFACE Gpsmodjk.pcx
FIGURE 3-13 MODEL 8179T TIMETAP RS-485

INTERFACE
FIGURE 3-14 TIMETALK RS-485 INTERFACE Resides in document
FIGURE 3-15 TIMEBURST RS-485 INTERFACE 81838185.pcx

FIGURE 4-1 COMMAND STRUCTURE Resides in document
FIGURE 4-2 TIME DIFFERENCE MAP Tzmap.eps (zipped)

FIGURE 5-1 MODEL 8226 IMPULSE SUPPRESSOR Impulseb.eps
FIGURE 5-2 MODEL 8227 INLINE AMPLIFIER Gpsamp.eps
FIGURE 5-3 CABLE GUIDELINES Cablgide.wmf
FIGURE 5-4 MODEL 8213 ANTENNA MOUNT 8226_a.eps

FIGURE A-1 IRIG B TIME CODE Irigb.pcx (zipped)
FIGURE A-2 IRIG E TIME CODE Irige.pcx (zipped)

Net-per.cgm

81838179.pcx

SECTION 1: GENERAL INFORMATION

1.0 INTRODUCTION

1.1 FEATURES

1.2 WARRANTY INFORMATION AND PRODUCT SUPPORT

1.3 MANUAL ERRATA AND SPECIAL DOCUMENTATION

1.4 UNPACKING

1.5 SPECIFICATIONS

GENERAL INFORMATION

1.0 INTRODUCTION

The Spectracom NetClock/GTP Master Clock, shown in Figure 1-1, is a precise,
traceable Global Time Provider. The NetClock/GTP receives and recovers time
information from the Global Positioning System (GPS) constellation of satellites.
The GPS constellation consists of 24 satellites placed in 6 orbital planes spaced
equally around the equator and inclined at a 55-degree angle. This design
assures reliable worldwide coverage 24 hours a day. Each satellite contains a
redundant system of highly accurate and stable atomic clock sources. The
satellite’s timing, orbital position and other system parameters are monitored and
controlled by ground stations maintained by the US Department of Defense and
US Naval Observatory.

The NetClock/GTP Master Clock provides timing outputs accurate to within 100
microseconds of UTC. Standard Master Clock outputs include RS-232,
RS-485, FAA Modified IRIG B and a one pulse per second. The NetClock/GTP
is ideally suited as a Master Clock in all applications requiring an accurate and
traceable time source. Typical applications include computer network timing,
utility billing, financial transactions, public safety and transportation.

FIGURE 1-1 NETCLOCK/GTP MASTER CLOCK

NetClock/GTP Instruction Manual Page 1-1

Section 1: General Information

1.1 FEATURES

The Spectracom NetClock/GTP offers the following features:

• RELIABLE WORLDWIDE COVERAGE: The NetClock/GTP can receive
and track up to eight satellites simultaneously.

• ACCURACY: The NetClock/GTP 1PPS output is within ± 500
nanoseconds of UTC. The time data outputs are within 100 microseconds
of UTC.

• MULTIPLE TIME DATA OUTPUTS: Each clock includes four FAA
modified pulse width coded IRIG B outputs. Two RS-232 and one RS-485
time data ports are also provided. Output data formats and baud rates are
configured using the RS-232 Setup port.

• REFERENCE FREQUENCY OUTPUT: The NetClock/GTP provides a 10
MHz output disciplined to received GPS signal. Output accuracy is
specified to within ± 1 x 10-8.

1.2 WARRANTY INFORMATION AND PRODUCT SUPPORT

Warranty information is found on the leading pages of this manual. Should it
become necessary to exercise the warranty, contact Spectracom Corporation to
obtain a replacement or service.

Spectracom continuously strives to improve its products and greatly appreciates
any and all customer feedback. Please direct any comments or questions
regarding application, operation, or service to Spectracom's Customer Service
Department. Customer service is available Monday - Friday from 8:30 A. M. to
5:00 P.M. Eastern Time at 585-321-5800.

In addition, please contact Customer Service to obtain a Return Material
Authorization Number (RMA#) before returning any instrument to Spectracom
Corporation. Please provide the serial number and failure symptoms.
Transportation to the factory is to be prepaid by the customer.

Product support is also available by e-mail. Questions on equipment operation
and applications may be e-mailed to Spectracom at:
[e-mail].

Visit our web page for product information, warranty registration, and upgrade
notices as they become available at:
http://www.spectracomcorp.com

Page 1-2 NetClock/GTP Instruction Manual

Section 1: General Information

1.3 MANUAL ERRATA AND SPECIAL DOCUMENTATION

Information concerning manual corrections or product changes occurring after
printing is found in the Errata Section. An erratum, when required, is found at the
end of this manual. Please review and incorporate changes into the manual
whenever an Errata Section is included.

Spectracom will make instrument modifications upon special request. The
documentation associated with any modification is provided in addition to this
manual.

1.4 UNPACKING

Upon receipt, carefully examine the carton and its contents. If there is damage to
the carton that results in damage to the unit, contact the carrier immediately.
Retain the carton and packing materials in the event the carrier wishes to witness
the shipping damage. Failing to report shipping damage immediately may forfeit
any claim against the carrier. In addition, notify Spectracom Corporation of
shipping damage or shortages, to obtain replacement or repair services.

Remove the packing list from the envelope on the outside of the carton. Check
the packing list against the contents to be sure all items have been received,
including an instruction manual and ancillary kit. Table 1-1 lists the items
included in the NetClock/GTP ancillary kit.

Description Part Number Quantity

Terminal Block, 3-position P13003 1

Fuse, 1.0 Amp, 3AG F001R0 1

TABLE 1-1 MODEL 8183A ANCILLARY KIT

NetClock/GTP Instruction Manual Page 1-3

Section 1: General Information

1.5 SPECIFICATIONS

This section contains specifications for the Model 8183A NetClock/GTP, Model
8225 GPS Antenna and antenna accessory products available from Spectracom.

1.5.1 Receiver

Received Standard: L1 C/A Code transmitted at 1575.42 MHz.

Satellites Tracked: Up to eight simultaneously.

Acquisition Time: Typically <20 minutes from cold start.

Acquisition Sensitivity: -105 dBm to -137 dBm.

Tracking Sensitivity: -139 dBm.

Timing Accuracy: <500 nanoseconds with Selective Availability

“SA” on.

Antenna Connector: BNC female.

1.5.2 Display

Display Type: Red LED.

Digit Height: 0.8 inches for day of the year, hours and minutes.

0.56 inches for seconds.

Display Options: 12 or 24-hour format, UTC or local time, enable

DST/STD time changes.

1.5.3 Status Indicators

Front panel bi-color LED’s indicates operational status.

GPS Lock: Indicates GPS satellite tracking status. Lamp is green

when the receiver has tracked at least one satellite
within the period allotted for the GPS Lock Alarm.
The lamp is red during initial operation or whenever a
GPS Lock Alarm or CPU Alarm is asserted. The GPS
Lock Alarm period is programmable up to 23 hours:
59 minutes: 59 seconds in 1-second increments.
Factory default is 15 minutes.

Page 1-4 NetClock/GTP Instruction Manual

Section 1: General Information

Time Sync: Indicates accuracy of time data outputs. Lamp is

green when the receiver has tracked at least one
satellite within the period allotted for the Time Sync
Alarm. The lamp is red during initial operation and
when a Time Sync Alarm is asserted. A red lamp
indicates the time data output accuracy may not be
within published specifications. Time Sync Alarm
period is programmable up to 23 hours: 59 minutes:
59 seconds in one-second increments. Factory
default is two hours.

1.5.4 RS-232 Serial Communication Ports

Signal: Selected data format in RS-232 levels when

interrogated by the connected device. The port may
also be configured for continuous once-per-second
output.

Connector: DB9 female, pin assignments conform to EIA/TIA-574

standard, data communication equipment (DCE).
Flow control is not supported.

Character structure: ASCII, 1 start, 8 data, 1 stop, and no parity.

Accuracy: Data stream on time marker within ± 100

microseconds of UTC for Formats 0, 1, 3, and 90
selected. Formats 2 and 4 are within ±1 millisecond
of UTC.

Configuration: Baud rate and output data formats are selected using

the Serial Setup Interface. Bit rate selections are
1200, 2400, 4800 and 9600 baud. There are six data
format selections available. In addition, time zone
offset, DST rule and interrogation character can be
configured. Each RS-232 Serial Comm port is
independently configurable.

1.5.5 RS-485 Remote Output

Signal: Selected data format in RS-485 levels, output once

per second.

Connector: Removable 3-position terminal block (supplied).

Character Structure: ASCII, 1 start, 8 data, 1 stop, and no parity.

NetClock/GTP Instruction Manual Page 1-5

Section 1: General Information

Accuracy: Data stream on time marker within ± 100

microseconds of UTC for Formats 0, 1, 3, and 90
selected. Formats 2 and 4 are within ±1 millisecond
of UTC.

Configuration: Baud rate and output data formats are selected using

the Serial Setup Interface. Bit rate selections are
1200, 2400, 4800, and 9600 baud. There are six data
format selections available. In addition, time zone
offset and DST rule can be configured.

1.5.6 FAA IRIG B Outputs

Signal: Pulse-width-coded FAA modified IRIG B in RS-

422/485 levels. Four buffered outputs provided. FAA
IRIG B modifications include satellite lock indicator
and error flags between Position Identifiers P5 and P6
and removal of the straight binary seconds data.

Accuracy: ±2 microseconds of UTC when locked to GPS.

Connector: DB25 Male. Connector pin-out is listed below:

Output 1: Pin 2 (IRIG-B+) Pin 9 (IRIG-B-)
Output 2: Pin 3 (IRIG-B+) Pin 10 (IRIG-B-)
Output 3: Pin 4 (IRIG-B+) Pin 11 (IRIG-B-)
Output 4: Pin 5 (IRIG-B+) Pin 12 (IRIG-B-)
Ground: Pins 1,7,24 and 25.

Configuration: The IRIG time data can be configured to reflect local

time. UTC time zone offset and DST rule selections
are applied to all four IRIG outputs.

1.5.7 1PPS Output

Signal: One pulse-per-second square wave derived from the

GPS receiver.

Signal Level: TTL compatible into high impedance loads, 1.5 V

base-to-peak into 50 ohms.

Pulse Width: 200 milliseconds.

Accuracy: Positive edge within ± 500 nanoseconds of UTC when

locked to GPS.

Connector: BNC female.

Page 1-6 NetClock/GTP Instruction Manual

Section 1: General Information

1.5.8 Standard 10 MHz Output

Signal: 10 MHz sinewave.

Signal Level: 350 mVrms into 50 ohms.

Harmonics: Better than 30 dB down.

Spurious: Better than -35 dB down.

Accuracy: ± 1 x 10-8 when tracking GPS and under constant

temperature and humidity.

Connector: BNC female.

1.5.9 Input Power

DC Input: 12 to 36 VDC, 6 Watts.

Connector: Banana jacks

Polarity: Red is positive (+V), Black is negative (-V).

1.5.10 Mechanical and Environmental

Dimensions: 1.75 H x 19.0 W x 10.0 D inches

(44 H x 483 W x 254 D mm).

Rack mount: EIA 19”, front panel mounting holes for one standard

rack unit.

Weight: 4.25 lbs. (2.0 kg).

Temperature: 0° to 50°C operating range.

1.5.11 Model 8225 GPS Antenna Specifications

1.5.11.1 Electrical Specifications

Type: Active, 30dB gain.

Frequency: 1575.42 MHz.

Temperature Range: -30° to 80° C (-22° to 176°F).

Connector: N type, Female.

Recommended Cable: RG-213.

Maximum Cable Length: 200 feet. Longer cable lengths require the Model

Power: 5 Volts, 27 milliamps, powered by receiver.

NetClock/GTP Instruction Manual Page 1-7

8227 Inline Amplifier.

Section 1: General Information

1.5.11.2 Mechanical Specifications

Assembled Length: 24 inches (61 cm)
Housing Diameter: 3.5 inches (8.9 cm).
Housing Material: PVC.
Assembled Weight: 1.3 lbs. (.60 kg).
Mounting: Hose clamps (furnished) on vent pipe.

1.5.12 Model 8226 Impulse Suppressor

Connectors: Type N Female.
Turn On Time: 4 nanoseconds for 2 kV/ns.
Turn On Voltage: +7 V, -1 VDC.
Frequency Range: 1.2 to 2.0 GHz.
VSWR: 1.1:1 or better.
Insertion Loss: 0.1 dB maximum.

1.5.13 Model 8227 Inline Amplifier

Connectors: Type N Female.

Gain: 20 ±3 dB.

VSWR: ≤1.5:1.
Power: 3 - 9 VDC, 7.5 ±1 milliamps.

1.5.14 MP10-0000-0001 Grounding Panel

Overall Size: 12.0 L x 18.0 W x 0.75 D inches

(305 H x 457 W x 19 D mm).

Ground Plate Size: 10.0 L x 15.0 W x 0.063 D inches

(254 H x 381 W x 1.6 D mm).

Ground Strap: 20 feet (6 m) of 1.5 inch (38 mm) wide copper strap.
Mounting: Mounting hardware, self-drilling screws, copper
clamps and copper paste are included.

1.5.15 CA07xxx GPS Antenna Coax

Connectors: Type N male both ends.

-FAA suffix changes one end to BNC male.
Cable Jacket: UV resistant, black non-contaminating PVC.

Temperature Range: -40° to 80° C (-40° to 176°F).
Min. Bend Radius: 5.0 inches (127 mm).

Page 1-8 NetClock/GTP Instruction Manual

SECTION 2: INSTALLATION

2.0 INTRODUCTION

2.1 MODEL 8225 GPS ANTENNA

2.2 ANTENNA CABLE

2.3 MODEL 8226 IMPULSE SUPPRESSOR

2.4 MP10-0000-0001 COPPER GRONDING PANEL

2.5 MODEL 8227 GPS INLINE AMPLIFIER

2.6 NETCLOCK/GPS PREPARATION FOR USE

2.7 INITIAL OPERATION

2.8 QUALIFYING THE INSTALLATION

INSTALLATION

2.0 INTRODUCTION

This section describes the installation of the Model 8225 GPS Antenna and related
accessories. This section also describes the NetClock/GTP preparation for use, initial
operation, installation, qualification and configuration. To ensure proper operation,
please read this section prior to equipment installation and usage.

2.1 MODEL 8225 GPS ANTENNA

The Model 8225 is an active antenna tuned to receive the GPS 1575.42 MHz L1 band
satellite broadcast. The received signals are passed through a narrow bandpass filter
and preamplifier within the antenna. The active antenna circuitry provides 30 dB of gain
and requires +5 VDC at 27 milliamps. This is provided by the NetClock/GTP receiver
over the antenna coax. Each antenna is terminated with a type “N” female connector.
The Model 8225 features a compact weatherproof design measuring 3.5 inches in
diameter.

2.1.1 Antenna Installation

The GPS antenna must be installed outdoors in a location where an unobstructed view
of the sky exists. Rooftops generally make good locations due to clear overhead sky
with views to the horizon. This type of location allows the antenna to see and track the
maximum number of satellites throughout the day. Installations with obstructed views
may prove operational, but can experience reduced reception quality and the inability to
simultaneously track the maximum number of satellites. In addition to clear sky
coverage, select a site that would not allow the antenna to become buried in drifted or
accumulated snow or ice. Avoid placing the GPS antenna in close proximity to
broadcast antennas whenever possible.

Each antenna includes a mating PVC mast assembly and two hose clamps to simplify
installation. The hose clamps can be used to affix the mast assembly to a vent pipe.
Spectracom offers an antenna base, Model 8213, for installations where vent pipe
mounting is not practical or desired. The Model 8213 is constructed of aluminum and is
furnished with ballast for stability. Both mounting methods are illustrated in Figure 2-1.

NetClock/GTP Instruction Manual Page 2-1

Section 2: Installation

FIGURE 2-1 ANTENNA INSTALLATION

2.2 ANTENNA CABLE

Spectracom recommends RG-213 type coax, such as Belden 8267, for the GPS
antenna cable. To simplify the installation process, Spectracom offers GPS cable
assemblies terminated with Type N male or BNC male connectors. Specify part number
CA07xxx, where xxx equals the length in feet, for a cable terminated with Type N
connectors. Adding the suffix –FAA changes one end of the antenna cable assembly to
a BNC male connector.

If the antenna cable is purchased locally, select coax suitable for outdoor use. Consider
the cable's weather resistance, temperature range, UV resistance, and attenuation
characteristics.

Do not allow the antenna cable to be placed in standing water, as water may permeate
through the coax jacket over time. On flat roof installations, the coax can be suspended
by cable hangers or placed in sealed PVC conduit. Apply a weather proofing sealant or
tape over all outdoor connections.

Installation of a surge protection device in the antenna line is recommended to protect
the NetClock/GTP receiver and connected devices from lightning damage. Spectracom
offers the Model 8226 Impulse Suppressor to shunt potentially damaging voltages on
the antenna coax to ground. Refer to Section 2.3 for a complete description of the
Model 8226.

Page 2-2 NetClock/GTP Instruction Manual

Section 2: Installation

2.2.1 Cable Lengths

Using Spectracom CA07xxx or Belden 8267 coax, the maximum antenna cable length
permitted is 200 feet. These cables attenuate the GPS signal by 10 dB per 100 feet of
coax. Installations requiring longer antenna cables may use the Model 8227 Inline
Amplifier, or lower loss cable. Refer to Section 2.5 for additional information on the
Model 8227.

When selecting alternate antenna cable sources, the attenuation characteristics at the
GPS frequency of 1575.42 MHz must be known. To ensure optimum receiver
performance, the total antenna cable attenuation must not exceed
20 dB. Cable attenuation of greater than 20 dB requires the use of a Model 8227 Inline
Amplifier.

2.3 MODEL 8226 IMPULSE SUPPRESSOR

Spectracom recommends the use of an inline coaxial protector for all products with an
outside antenna. Spectracom offers the Model 8226, Impulse Suppressor, to protect
the receiver from damaging voltages occurring on the antenna coax. Voltages
exceeding the impulse suppresser trip point are shunted to the system ground. The
Model 8226 is designed to withstand multiple surges.

Mount the suppressor indoors, preferably where the coax enters the building. Install the
suppressor on a grounding panel or bulkhead using the BF adapter bracket
(Spectracom part # MP10-0000-0002) as shown in Figure 2-2.

PART #: MP10-0000-0002

INSTALL RUBBER

WASHER

FIGURE 2-2 MODEL 8226 IMPULSE SUPPRESSOR

Refer to Section 2.4 for additional information on the copper grounding panel (part #
MP10-0000-0001) offered by Spectracom.

NetClock/GTP Instruction Manual Page 2-3

Section 2: Installation

Each Model 8226 includes two clamp type male N connectors. These connectors can
be used to splice the Model 8226 into the antenna coax. The connectors are
compatible with RG-213 type coax such as Spectracom CA07xxx or Belden 8267.
Connector assembly instructions are shown in Figure 2-3.

FIGURE 2-3 CONNECTOR ASSEMBLY INSTRUCTIONS

Page 2-4 NetClock/GTP Instruction Manual

Section 2: Installation

2.4 MP10-0000-0001 COPPER GROUNDING PANEL

A single point ground system is recommended to provide optimum protection from
lightning strikes. Spectracom offers a copper grounding panel, part number MP10­0000-0001, as a single point ground connection for the antenna surge suppressor,
equipment rack, GPS receiver and other surge protection devices to a perimeter ground
system.

Each grounding panel includes mounting hardware, hardware to secure protective
devices to the copper plate, 20 feet of 1.5 inch wide copper strap, two strap clamps and
copper paste.

Mount the grounding panel indoors, preferably close to where the antenna coax enters
the building and direct access to the system ground is available. Refer to Figure 2-4 for
installation guidelines. The ground panel must be connected to a low impedance (both
low resistance and low inductance) ground system to assure proper operation of the
surge protection equipment. To minimize the inductance between the ground plate and
system ground interconnection keep the copper grounding strap as straight as possible,
limit bends to a radius of 8 inches or larger. Thoroughly clean the copper panel to
remove any oxidation or contaminants prior to installation. Apply the supplied copper
paste to all junctions on the copper panel to maintain a low impedance connection.

FIGURE 2-4 GROUNDING PANEL INSTALLATION

NetClock/GTP Instruction Manual Page 2-5

Section 2: Installation

2.5 MODEL 8227 GPS INLINE AMPLIFIER

An inline amplifier is required whenever GPS antenna cable lengths cause greater than
20 dB attenuation. Using Spectracom CA07xxx or Belden 8267 coax, an amplifier is
needed whenever antenna cable lengths exceed 200 feet.

The Model 8227 GPS Inline Amplifier, shown in Figure 2-5, extends the maximum cable
length to 400 feet. The Model 8227 provides 20 dB of gain and is powered by the
NetClock/GTP receiver.

FIGURE 2-5 MODEL 8227 INLINE AMPLIFIER

Each Model 8227 includes two clamp type male N connectors. These connectors can
be used to splice the Model 8227 into the antenna coax. The connectors are
compatible with RG-213 type coax such as Spectracom CA07xxx or Belden 8267.
Refer to Figure 2-3 for connector assembly instructions.

A five-foot long coaxial cable is also provided with each Model 8227. This cable
connects the amplifier to the surge suppressor. This cable is rated for indoor usage
only.

Refer to Figure 2-6 for Model 8227 installation guidelines. The cable lengths shown in
Figure 2-6 represent Spectracom CA07xxx cable. The equivalent cable loss expressed
in dB, is provided for use with other cables.

Place the inline amplifier within 100 feet (10 dB cable loss) of the antenna to optimize
the signal to noise ratio. Whenever possible, install the inline amplifier indoors after the
impulse suppressor using the supplied 5-foot cable. The amplifier can be installed
outdoors, providing care is taken to weatherproof the connections. Due to unique
system dynamics of the antenna, amplifier and receiver, a minimum of cable length of
200 feet (20 dB cable loss) is required to prevent overloading the receiver.

Page 2-6 NetClock/GTP Instruction Manual

Section 2: Installation

FIGURE 2-6 CABLE GUIDELINES

2.6 NETCLOCK/GTP PREPARATION FOR USE

This section outlines the set-up procedure to prepare the NetClock/GTP for operation.

2.6.1 Antenna Connection

Install the Model 8225 Antenna as outlined previously in this section. Connect the
antenna cable to the rear panel GPS ANTENNA connector.

2.6.2 Power Connection

The NetClock/GTP can be powered from a 12 to 36 VDC power source. Power
consumption is 6 Watts. Power is applied to the rear panel banana jacks; Red is for
positive polarity and Black is negative. Place the front panel power switch in the OFF
position before applying power.

Note: The NetClock/GTP utilizes a locking toggle power
switch. To actuate the switch, first pull on the switch knob,
then move to the desired position ON or OFF, then release.

NetClock/GTP Instruction Manual Page 2-7

Section 2: Installation

2.6.3 Chassis Ground

The chassis ground lug allows the NetClock/GTP chassis to be connected to an earth
ground or single point ground. Connecting the chassis to a single point ground system
may be required in some installations to ensure optimum lightning protection. An earth
ground is also recommended in installations where excessive noise on the power line
degrades receiver performance.

2.6.4 Configuration

The NetClock/GTP time outputs and operational parameters are configurable to meet
the requirements of many applications. Baud rate and time data format selections of
the RS-232 and RS-485 ports, front panel display format, Daylight Saving Time and
time difference from UTC are just some of the configuration selections.

Most applications of the NetClock/GTP will set the clock display and time data outputs
to reflect local time. The default settings for all outputs are UTC time with no Daylight
Saving Time rule implemented.

Commands to configure the clock are entered through the RS-232 Serial Setup
Interface port. Connect a computer running a terminal emulation program
(HyperTerminal, ProComm, etc.) to the Serial Setup Interface port. Connect using a
straight through (1 to 1 pinning) RS-232 serial cable. Configure the terminal for ANSI
emulation, 9600 baud, 8 data, 1 stop, no parity and XON/OFF flow control.

To view the current configuration of the NetClock/GPS display and time data outputs
issue the configuration command, CONF as shown below:

Type: conf <ent>

Default Response:

FRONT PANEL FORMAT= 24 HOUR
TIME DIFF= +00:00 DST= 0

IRIG FORMAT= FAA
TIME DIFF= +00:00 DST= 0

SERIAL PORT 1
BAUD RATE= 9600 FORMAT #= 00 REQUEST CHAR= T
TIME DIFF= +00:00 DST= 0

SERIAL PORT 2
BAUD RATE= 9600 FORMAT #= 00 REQUEST CHAR= T
TIME DIFF= +00:00 DST= 0

REMOTE PORT 1
BAUD RATE= 9600 FORMAT #= 00
TIME DIFF= +00:00 DST= 0

Page 2-8 NetClock/GTP Instruction Manual

Section 2: Installation

The following paragraphs contain configuration examples of the front panel display,
IRIG, RS-232 serial communication ports and the RS-485 Remote Output.
Configuration entries or keystrokes are shown in BOLD ITALICS. Commands are
terminated or executed by the enter key <ent>. The responses from the NetClock/GTP
are shown in ITALICS.

2.6.4.1 Front Panel Display Configuration

The command, FPF, reads and sets the front panel display configuration. Display
options include 12 or 24 hour display format, UTC or local time with or without DST
corrections.

To allow configuration changes, place the clock in Set Mode as shown below:

Type: SM ON <ent>
Response: SET MODE ON

The front panel display format is configured using the FPF. The command structure is
shown below:

Type: FPF [12:24] [±HH:MM] [DST] <ent>

Where: 12 = 12 Hour Display Format

24 = 24 Hour Display Format

±HH:MM = Time Difference from UTC, ±00:00...±12:00

Where: -00:00 = UTC

-04:00 = Atlantic

-05:00 = Eastern

-06:00 = Central

-07:00 = Mountain

-08:00 = Pacific
Refer to Figure 4-2, UTC Time Difference Map, for additional

offsets.

DST = DST rule number, 0...6.

Where: 0 = No DST, Always Standard Time

1 = North American

2 = United Kingdom
3 = Continental Europe
4 = China
5 = Australian 1
6 = Australian 2

NetClock/GTP Instruction Manual Page 2-9

Section 2: Installation

Example: Configure the front panel display for 24 hour format, Eastern Time with

Daylight Saving Time.
Type: SM ON <ent>
Response: SET MODE ON
Type: FPF 24 -05:00 1 <ent>
Response: FRONT PANEL FORMAT = 24 HOUR

TIME DIFF = -05:00 DST = 1

2.6.4.2 IRIG Configuration

Time data contained in the IRIG outputs can be configured to provide local time with or
without DST corrections using the command IRIG.

Note: The IRIG command programs all four IRIG outputs to the same configuration.

The IRIG command structure is shown below:

Type: IRIG [TD] [DST] <ent>

Where: TD = Time Difference from UTC, ±00:00...±12:00

Where: -00:00 = UTC

-04:00 = Atlantic

-05:00 = Eastern

-06:00 = Central

-07:00 = Mountain

-08:00 = Pacific
Refer to Figure 4-2, UTC Time Difference Map, for additional

offsets.

DST = DST rule number, 0...6.

Where: 0 = No DST, Always Standard Time

1 = North American

2 = United Kingdom
3 = Continental Europe
4 = China
5 = Australian 1
6 = Australian 2

Example: Configure the time contained in the IRIG outputs to reflect Pacific Time

with DST corrections.

Type: SM ON <ent> (Set Mode may already be enabled)
Response:

SET MODE ON

Type: IRIG -08:00 1 <ent>
Response:

IRIG FORMAT= FAA
TIME DIFF = -08:00 DST = 1

Page 2-10
NetClock/GTP Instruction Manual

Section 2: Installation

2.6.4.3 RS-232 Serial Comm and RS-485 Remote Output Configuration

The NetClock/GTP has several time data formats available to suit various applications.
Data Formats 0, 1 and 3 can be configured to provide local time with or without Daylight
Savings Time corrections. Data formats 2, 4, and 90 always reflect UTC time. Refer to
section 3.3 for a complete description of available data formats. Bit rate can be
programmed from 1200 to 9600 baud. In addition, the serial ports can be configured to
output the selected dated format upon receiving a time request character or
continuously once-per-second. The Remote Output always outputs the selected data
format once-per-second.

The two RS-232 Serial Comm ports are individually programmable. The command
SER1 reads or sets the Serial Comm 1 configuration and SER2 configures Serial
Comm 2. The command REM1 configures the RS-485 Remote Output port. The SER
and REM1 command structures are shown below:

SER[X] [BAUD] [FMT] [REQ] [TD] [DST] <ent>

REM1 [BAUD] [FMT] [TD] [DST] <ent>

Where: X = Serial Comm Number:1,2
BAUD = Baud Rate: 1200, 2400, 4800, 9600
FMT = Data Format: 00, 01, 02, 03, 04, 90. Most

applications use Format 00 or 02. Refer to Section 3.3
for a complete description of the data formats.

REQ = Request Character. Any symbol, number or letter can

be configured as the request character. The Serial
Comm port will output the selected data format upon
receiving this character.
Most applications use a capital letter "T". The
RS-232 Comm port can also be configured to output
continuously once-per-second by typing the word
NONE as the request character.

TD = Time Difference from UTC, ±00:00...±12:00

Where: -00:00 = UTC

-04:00 = Atlantic

-05:00 = Eastern

-06:00 = Central

-07:00 = Mountain

-08:00 = Pacific
Refer to Figure 4-2, UTC Time Difference Map, for additional

offsets.

DST = DST rule number, 0...6.

NetClock/GTP Instruction Manual Page 2-11

Section 2: Installation

Where: 0 = No DST, always Standard Time
1 = North America
2 = United Kingdom
3 = Continental Europe
4 = China
5 = Australian 1
6 = Australian 2

Example: Set the Serial Comm 1 to respond with Data Format 02 whenever a T is

received. Set the bit rate at 9600 Baud and time reflecting UTC time
without DST corrections.

Type: SM ON <ent> (Set Mode may already be enabled)
Response:

Type: SER1 9600 02 T -00:00 0 <ent>

SET MODE ON

Response: SERIAL PORT 1

BAUD RATE = 9600 FORMAT # = 02 REQUEST CHAR = T

TIME DIFF = -00:00 DST = 0

Example: Set the Remote Output to provide Format 00 at 9600 baud and time

reflecting Central Time with DST corrections.

Type: SM ON <ent> (Set Mode may already be enabled)
Response: SET MODE ON

Type: REM1 9600 00 -06:00 1 <ent>

Response: REMOTE PORT 1

BAUD RATE = 9600 FORMAT # = 00

TIME DIFF = -06:00 DST = 1

2.7 INITIAL OPERATION

During initial operation, the GPS LOCK and TIME SYNC lamps are red. The initial clock
time is derived from the nonvolatile RAM/Timekeeping integrated circuit. The receiver
will now acquire and lock to GPS satellites currently in view of the antenna. If the
receiver is unable to acquire a satellite within 15 minutes a GPS Lock Alarm is asserted
causing an RS-232 alarm log entry.

The GPS LOCK lamp turns green after tracking at least one satellite for one minute.
The TIME SYNC lamp remains red until the receiver has acquired the complete system
almanac from at least one satellite. Typically, the entire process of acquiring satellites
and retrieving the almanac requires 20 minutes to accomplish. Once the GPS LOCK
and TIME SYNC lamps turn green the NetClock/GTP shall operate in accordance with
the specifications published in this manual.

Page 2-12
NetClock/GTP Instruction Manual

Section 2: Installation

2.8 QUALIFYING THE INSTALLATION

Typically, the front panel TIME SYNC lamp turns green within 20 minutes of power on.
This lamp indicates that receiver is tracking at least one qualified satellite. If the GPS
LOCK lamp does not change from red to green, a cable or reception problem may exist.
Refer to Section 5.1 for troubleshooting assistance.

Reception quality can be evaluated using the performance and status logs provided by
the receiver. Commands to retrieve operational information are issued through the rear
panel RS-232 Serial Setup Interface port. To communicate with the receiver, a terminal
or computer with terminal emulation software (i.e. ProComm Plus, Hyper-Terminal, etc.)
is required. Configure the terminal for ANSI emulation, 9600 baud and a character
structure of 1 start, 8 data, 1 stop and no parity. XON/XOFF flow control is supported.

2.8.1 GPS Signal Status

The GPS Signal Status command, GSS, provides an instantaneous view of the GPS
reception quality. This command is used to verify proper antenna placement and
receiver performance of an installation. The GSS response indicates the number of
satellites the receiver is currently tracking and their relative signal strength. The
resulting GPS quality and Position Fix Status are also included. A complete description
of the GSS command can be found in Section 4 of this manual.

Issue the GSS command as shown below.

Type: GSS <ent>

An example response is shown below:

TRACKING 4 SATELLITES

GPS STATE= 3D-FIX DOP= 03.7
LATITUDE= N 43 06 59.746 LONGITUDE= W 077 29 15.242 HEIGHT= +00110 METERS
QUALITY= PASSED

CHAN VID MODE STREN STAT
01 24 08 043 A2
02 04 08 029 A2
03 10 00 000 00
04 05 08 053 A2
05 18 00 000 00
06 30 00 000 00
07 01 08 047 A2
08 06 00 000 00

NetClock/GTP Instruction Manual Page 2-13

Section 2: Installation

Tracking: The receiver must track at least one qualified satellite to operate. Typically,

the receiver shall track 6 or more satellites with the Model 8225 GPS Antenna. If the
Model 8228 indoor window mount antenna is used, the receiver will typically track 4
or more satellites.

GPS State: Under normal operation the receiver will indicate 3-D Fix. A Searching or

2-D Fix message indicates that fewer than 4 qualified satellites are currently tracked.

DOP: Dilution of Precision indicates the degree of uncertainty of a Position Fix. The

DOP value shall be 0≤DOP<10 when in 3-D Fix mode.

Quality: A PASSED message indicates the receiver is tracking at least one qualified

satellite. A FAILED message indicates the received GPS signals did not meet
minimum requirements.

Satellite Data: Data on each satellite currently tracked is provided in table form.

The CHAN column represents the GPS Receiver Channel Number, 1 through 8.

VID is the Vehicle (satellite) Identification Number, 1 through 37.

The MODE column provides the Channel Tracking Mode for each satellite. The GPS
qualifying algorithm accepts only satellites having a Mode value of 08.

The relative signal strength of each satellite currently tracked is found in the STREN
column. The maximum signal level is 55.

The satellite status flag code is found in the STAT column. Typically, the STAT value is
A2.

If the receiver does not meet the minimum requirements described above, refer to
Section 5, Service Information, for troubleshooting assistance.

2.8.2 Tracking Histogram

The D

isplay Tracking Histogram command, DH, is used to evaluate the long term
reception quality. The tracking histogram records the number of satellites tracked and
qualified every second. At the end of the hour, a log is created and the counters are
restarted. The command responds with the last four hourly entries and the histogram
currently in process. A complete description of the DH command is found in Section 4
of this manual.

Allow the receiver to operate for at least 5 hours before evaluating the tracking
histogram. Issue the DH command as shown below:

Type: DH <ent>

Page 2-14
NetClock/GTP Instruction Manual

Section 2: Installation

An example response is shown below:

TIME= 16:00:00 DATE= 2000-05-11 QUALIFIED HISTOGRAM
0= 00000 1= 00026 2= 00287 3= 03287 4= 00000
5= 00000 6= 00000 7= 00000 8= 00000 Q= 03600

TIME= 17:00:00 DATE= 2000-05-11 QUALIFIED HISTOGRAM
0= 00000 1= 00000 2= 00429 3= 02292 4= 00879
5= 00000 6= 00000 7= 00000 8= 00000 Q= 03600

TIME= 18:00:00 DATE= 2000-05-11 QUALIFIED HISTOGRAM
0= 00000 1= 00087 2= 00693 3= 02761 4= 00059
5= 00000 6= 00000 7= 00000 8= 00000 Q= 03600

TIME= 19:00:00 DATE= 2000-05-11 QUALIFIED HISTOGRAM
0= 00026 1= 00382 2= 00947 3= 02245 4= 00000
5= 00000 6= 00000 7= 00000 8= 00000 Q= 03574

TIME= 19:49:45 DATE= 2000-05-11 QUALIFIED HISTOGRAM
0= 00000 1= 00267 2= 01374 3= 01344 4= 00000
5= 00000 6= 00000 7= 00000 8= 00000 Q= 02985

In this example, the receiver tracked one satellite for 26 seconds, two satellites for 287
seconds and three satellites for 3287 seconds for the hour ending 16:00:00. The "Q"
value of 3600 indicates the receiver had tracked at least one qualified satellite for the
entire hour (3600 seconds). Note the partial histogram shown in the time stamp of
19:49:45.

For optimum performance, the receiver should consistently track three or more
satellites. The Q value should typically be 3600 for most entries. Occasional drops
below 3600 are considered acceptable. If the majority of the histograms show tracking
less than three satellites or Q values less than 3000, the receiver may not provide
reliable operation. Refer to Section 5.1, Reception Troubleshooting, for
recommendations.

NetClock/GTP Instruction Manual Page 2-15

SECTION 3: OPERATION

3.0 INTRODUCTION

3.1 FRONT PANEL FUNCTIONS

3.2 REAR PANEL FUNCTIONS

3.3 DATA FORMAT DESCRIPTION

3.4 REMOTE OUTPUT USAGE

OPERATION

3.0 INTRODUCTION

This section describes the front and rear panel functions and operational
information for the NetClock/GTP.

3.1 FRONT PANEL FUNCTIONS

Refer to Figure 3-1, NetClock/GTP Front Panel, and the following paragraphs for
front panel functions.

3.1.1 Display

The front panel display provides GPS synchronized time. The display characters
are red LED digits measuring 0.8 inches high for the day of year, hours and
minutes, and 0.56 inches for the seconds. The display area features a red filter
with an anti-glare surface for optimum viewing.

Day of the year value is displayed in the three left-hand digits. The day values
range from 001 to 366 for leap years. Leading zeroes are not suppressed.

The time display can be configured for 12 or 24 hour format, Coordinated
Universal Time (UTC) or local time with or without Daylight Saving Time
corrections. The command FPF configures the front panel display format
options. Refer to Section 4, Software Commands, for a complete description of
this command.

In addition to providing time, the display communicates when an adjust oscillator
alarm is activated by displaying all 8’s every three seconds. This alarm warns
that the GPS disciplined TCXO time base requires an adjustment to ensure
proper operation. The adjustment compensates for crystal aging and centers the
TCXO within its control range. Typically, this adjustment is not necessary until
after many years of operation. Refer to Section 5, Service Information, for the
TCXO adjustment procedure.

3.1.2 GPS Lock Lamp

This bi-color LED indicates the receiver lock status to GPS. At power on this
lamp is red. The lamp turns green after the receiver has tracked and qualified at
least one satellite for one minute.

NetClock/GPS Instruction Manual Page 3-1

Section 3: Operation

FIGURE 3-1 NETCLOCK/GTP FRONT PANEL

Page 3-2 NetClock/GTP Instruction Manual

Section 3: Operation

The lamp remains green if the receiver continues to track, or has tracked, at least
one qualified satellite within the period allotted for the GPS Lock Alarm. The
default period is set for 15 minutes. The GPS Lock Alarm period can be
configured up to 24 hours using the LOCK command. Refer to Section 4 for a
complete description of the LOCK command.

The lamp turns red when the receiver is unable to track any satellites and the
GPS Lock period has expired. At this point a GPS Lock Alarm message is output
on the Serial Setup port.

After the receiver reacquires at least one qualified satellite for one minute, the
GPS Lock lamp turns green. Another status message is sent to the Serial Setup
port that the GPS Lock Alarm has been cleared.

Refer to Section 3.2.8 for additional information on the GPS Lock Alarm.

3.1.3 Time Sync Lamp

This bi-color LED indicates the time synchronization status to GPS. At power on
this lamp is red, indicating that the clock is not synchronized and time data
accuracy does not meet specification.

The lamp turns green when the receiver has acquired at least one satellite and
has recovered the GPS system almanac. The entire GPS system almanac takes

12.5 minutes to transmit. The time data accuracy shall now conform to
specifications. The lamp remains green if the receiver continues to track, or has
tracked, at least one qualified satellite within the period allotted for the Time Sync
Alarm. The default period is two hours. The duration of the Time Sync Alarm
period is dependent on the accuracy requirement of the application. The Time
Sync Alarm period can be configured up to 24 hours using the SYNC command.
Refer to Section 4 for a complete description of the SYNC command.

The lamp turns red when the receiver is unable to track any satellites and the
Time Sync Alarm period has expired. At this point, a Time Sync Alarm message
is output on the Serial Setup port to warn that time data accuracy may be
compromised.

The lamp returns to green only upon acquiring and qualifying at least one
satellite for 1 minute if the almanac data is still valid. If the almanac is invalid or
lost due to a power failure, the clock will have to again recover the complete
almanac (12.5 minutes). When the receiver reacquires Time Sync, a status
message is sent to the Serial Setup port that the Time Sync Alarm has been
cleared and timing accuracy shall meet specification. Refer to Section 3.2.8 for
additional information on the Time Sync Alarm.

NetClock/GTP Instruction Manual Page 3-3

Section 3: Operation

3.2 REAR PANEL FUNCTIONS

Refer to Figure 3-2, NetClock/GTP Rear Panel, and the following paragraphs for
rear panel functions.

3.2.1 GPS Antenna

This BNC connector is the antenna input to the GPS receiver. The Model 8225
GPS Antenna and the Model 8227 Inline Preamplifier receive operational power,
+5 VDC, from this connector.

3.2.2 Standard 10 MHz Output

The STD 10 MHz Output BNC connector provides a 10 MHz sinewave derived
from the GPS disciplined TCXO time base. Frequency accuracy is better than 1

-8

x 10

(±0.1 Hz). Signal level is 350 mVrms into 50 ohms. The 10 MHz output
may be used as a time base for signal generators, frequency counters or other
devices accepting an external reference frequency.

3.2.3 1PPS Output

This BNC connector provides a GPS derived one pulse-per-second output. The
leading edge of this TTL compatible signal is within ± 500 nanoseconds of UTC
with selective availability (SA) on. The leading edge can be adjusted to
compensate for antenna cable delays using the command ACD.

Refer to Section 4, Software Commands, for additional information on the ACD
command.

Page 3-4 NetClock/GTP Instruction Manual

Section 3: Operation

FIGURE 3-2 NETCLOCK/GTP REAR PANEL

NetClock/GTP Instruction Manual Page 3-5

Section 3: Operation

3.2.4 FAA IRIG-B Outputs

IRIG is an acronym for Inter-Range Instrumentation Group. In the late 1950’s
this group created a series of time code standards suitable for use with recording
oscillographs, magnetic tape and real time transmission. Each IRIG code
specifies a carrier frequency that is modulated to encode date and time, as well
as control bits to time stamp events. Initially, IRIG applications were primarily
military and government associated. Today, IRIG is commonly used to
synchronize voice loggers, Mode-S radar and sequential event loggers found in
emergency dispatch centers, air traffic control towers and power utilities.

The NetClock/GTP provides four pulse-width-coded FAA modified IRIG B in RS­422/485 levels. FAA IRIG B modifications include satellite lock indicator and
error flags between Position Identifiers P5 and P6 and removal of the straight
binary seconds data. Refer Appendix A of this manual for detailed information on
the FAA modified IRIG B code.

The IRIG time data can be configured to reflect local time using the command
IRIG. UTC time zone offset and DST rule selections are applied to all four IRIG
outputs. Refer to Section 4, Software Commands, for a complete description of
this command.

The four FAA modified IRIG B signals are output on the 25-pin series D male
connector. Connector pin numbering is shown in Figure 3-3. Pin assignments
are listed in Table 3-1.

FIGURE 3-3 IRIG CONNECTOR

OUTPUT # IRIG + IRIG -

Output 1 Pin 2 Pin 9

Output 2 Pin 3 Pin 10

Output 3 Pin 4 Pin 11

Output 4 Pin 5 Pin 12

Pins 1, 7, 24 and 25 are grounded.

Page 3-6 NetClock/GTP Instruction Manual

TABLE 3-1 IRIG PIN OUT

Section 3: Operation

3.2.5 RS-232 Serial Communication Ports

The NetClock/GTP has two serial communication ports labeled Serial Comm 1
and Serial Comm 2. These ports provide an ASCII RS-232 data stream in the
selected data format. There are five time data format selections and one position
data stream in NMEA 0183 format available. Refer to Section 3.3 for a complete
description of each data format. In addition to data formats, baud rate, UTC time
difference and operation mode of both ports are selectable. A port may be
enabled to output when interrogated by the connected device or continuously
every second.

When using the Serial Comm ports in the interrogation mode, any keyboard
symbol, number or upper case letter may be configured to request the time. The
factory default request character is a capital letter T. NetClock/GTP responds
with an asterisk (*) to all invalid commands or characters received. Do not follow
a time request character with a line terminator (carriage return, enter, etc.).

The serial communication ports are configured by the commands SER1 and
SER2. Refer to Section 4, Software Commands, for a complete description of
these commands.

The Serial Comm connectors are 9-pin series D females. Connector pin
numbering is shown in Figure 3-4. Serial Comm pin assignments are listed in
Table 3-2.

FIGURE 3-4 SERIAL COMM PIN NUMBERING

PIN SIGNAL I/O DESCRIPTION

2 RXD O Receive Data

3 TXD I Transmit Data

5 GND - Signal Common

6 DSR O Data Set Ready

7 RTS * Request to Send

8 CTS * Clear to Send

*Pins 7 and 8 are connected together internally.

TABLE 3-2 SERIAL COMM PIN ASSIGNMENTS

NetClock/GTP Instruction Manual Page 3-7

Section 3: Operation

Per EIA/TIA-574 standard, the NetClock/GTP Serial Comm ports are classified a
data circuit-terminating equipment or DCE. Data is output on Pin 2, RXD and
time commands are input on Pin 3, TXD. When connecting to data terminal
equipment, DTE, (i.e. a personal computer) a one-to-one cable is used.
Interfacing to a DCE requires reversing Pins 2 and 3 or a null modem. The Serial
Comm ports require no flow control. The Request to Send and Clear to Send
signals are internally connected together, and the DSR signal is held high
through a pull-up resistor. The character structure is set for no parity, 8 data bits
and 1 stop bit.

3.2.6 RS-485 Remote Output

The NetClock/GTP Remote Output provides a continuous RS-485 once-per­second time data stream in the selected data format. There are five time data
format selections and one position data stream in NMEA 0183 format available.
Refer to Section 3.3 for a complete description of the data format structures.

In addition to data formats, baud rate and UTC time difference of each output is
selectable. The command REM1 configures the port setup. Refer to Section 4
for a complete description of this command.

The mating 3-position terminal block is supplied in the ancillary kit. Connector
pin assignments are shown in Figure 3-5.

RS-485

-

+

12

FIGURE 3-5 REMOTE OUTPUT

G

3

Page 3-8 NetClock/GTP Instruction Manual

Section 3: Operation

RS-485 is a balanced differential transmission requiring twisted pair cabling.
RS-485 characteristics make it ideal to distribute time data throughout a facility.
The Remote Output can provide time to 32 devices at cable lengths up to 4000
feet. Refer to Figure 3-6 for a schematic representation of the RS-485 output
driver. Relative to RS-485 specifications, the A terminal (Pin 2) is negative with
respect to the B terminal (Pin 1) for a mark or binary 1. The A terminal is positive
to the B terminal for a space or binary 0.

Shield

B

1

B Terminal (+)

A Terminal (-)

2

A

3

FIGURE 3-6 RS-485 OUTPUT

Spectracom offers many devices that accept the RS-485 data stream as an input
reference. These products include display clocks, RS-485 to RS-232 converters,
NTP time provider, talking clocks and radio link products to meet various time
applications and requirements. For information on Remote Output usage refer to
Section 3.4 of this chapter.

3.2.7 Serial Setup Interface

The Serial Setup Interface is an RS-232 communication port. Commands to
configure output signal options, set operational parameters, perform test
functions, view receiver performance and clock configuration are entered here.
Refer to Section 4, Software Commands, for a complete description of the
NetClock/GTP command set.

The Serial Setup Interface connector is a 9-pin series D female. Connector pin
numbering is shown in Figure 3-7. Pin assignments are listed in Table 3-3.

NetClock/GTP Instruction Manual Page 3-9

FIGURE 3-7 PIN NUMBERING

Section 3: Operation

PIN SIGNAL I/O DESCRIPTION

2 RXD O Receive Data

3 TXD I Transmit Data

5 GND - Signal Common

6 DSR O Data Set Ready

7 RTS * Request to Send

8 CTS * Clear to Send

*Pins 7 and 8 are connected together internally.

TABLE 3-3 PIN ASSIGNMENTS

The Serial Setup Interface communicates at 9600 baud with a character structure
of 8 data bits, no parity, and 1 stop bit. Per EIA/TIA 574 standard, the setup port
is classified as a data circuit-terminating equipment or DCE. Data is output on
Pin 2, RXD and commands are input on Pin 3, TXD. When connecting to data
terminal equipment, DTE, (i.e. a personal computer) a one to one cable is used.
Interfacing to another DCE device (i.e. a modem) requires a null modem
connection. Flow control is not required, though XON/XOFF is supported. The
Request to Send (RTS) and Clear to Send (CTS) lines are internally connected
together. Data Set Ready, DSR, is continuously held high by a pull up resistor.

The Serial Setup Interface is also used to update the flash memory with new
code. This feature allows implementation of new features or code changes into
field installed units. Upgrade announcements are posted on the Spectracom
WEB page as they become available. The Internet address is
www.spectracomcorp.com. A read me file is included in the batch file to provide
the necessary instructions. Upgrades may also be provided on disk on a request
basis only. Contact Spectracom customer service for upgrade requests and
information.

3.2.8 Status Messages

Changes in operational status messages are automatically provided to the Serial
Setup port. The NetClock/GTP divides alarm conditions into two categories,
Major and Minor. A Major Alarm is asserted when fault conditions exist which
affect the operation or accuracy of the unit. A Minor Alarm warns of conditions
having no immediate effect on total operation, but may require corrective action.

In addition to the automatic status messages, operational status and alarm log
history can be monitored using the Serial Setup Interface commands STAT and
DAL. These commands are described in Section 4 of this manual.

Page 3-10 NetClock/GTP Instruction Manual

Section 3: Operation

A status message classified as a Major Alarm is output when the following
alarms and conditions exist:

Frequency Alarm: Measured oscillator frequency error exceeds 1 x 10

-7

.

Time Sync Alarm: The period of time allotted for operation without tracking a

satellite has expired. Factory default period is 2 hours. The
time sync period is programmable from 1 minute to 23 hours:
59 minutes: 59 seconds using the SYNC command
described in Section 4, Software Commands.

CPU Fault: The CPU is unable to communicate with the GPS receiver.

Test Mode: Unit is placed in Test Mode operation.

Power Failure: The NetClock/GTP has lost power.

A status message classified as a Minor Alarm is output when the following
alarms and conditions exist:

Oscillator Adjust: Warns that oscillator is operating within 10% of the

minimum or maximum control setting. The oscillator
requires manual adjustment.

GPS Lock Alarm: The period of time allotted for operation without

tracking a satellite has expired. Factory default is 15
minutes. The GPS lock period is programmable from
1 minute to 23 hours: 59 minutes: 59 seconds using
the LOCK command described in Section 4, Software
Commands.

Antenna Problem: The antenna sense circuitry warns when the antenna

SmartWatch Invalid: A failure has been detected with the non-volatile

Test Mode: Unit is placed in Test Mode operation.

NetClock/GTP Instruction Manual Page 3-11

is not connected or a cable short or open is detected.

RAM/Timekeeping integrated circuit. Memory is
retained using lithium batteries having a minimum life
expectancy of ten years. Contact Spectracom for IC
replacement.

Section 3: Operation

3.2.9 DC Power

The NetClock/GTP can be powered from a 12 to 36 VDC power source. Power
consumption is 6 Watts. Connect the positive power connection to the red
bannana jack and the negative to the black.

The unit is fuse protected and controlled by the front panel locking toggle power
switch.

3.2.10 Chassis Ground

The chassis ground lug allows the clock chassis to be connected to a single point
grounding system. Connecting the chassis to a single point ground system may
be required in some installations to ensure optimum lightning protection. A
separate earth ground is also recommended in installations where excessive
noise on the power line degrades the GPS receiver performance.

3.3 DATA FORMAT DESCRIPTION

This section describes each of the data format selections available on the
NetClock/GTP Serial Comm and RS-485 Outputs. Format selection is made as
part of the Serial Comm and Remote port configuration. Most applications utilize
Data Format 0 or Data Format 2.

Page 3-12 NetClock/GTP Instruction Manual

Section 3: Operation

3.3.1 Format 0

Format 0 includes a time sync status character, day of year, time reflecting time
zone offset and DST corrections when enabled. Format 0 also includes the
DST/Standard Time indicator, and the time zone offset value. Format 0 data
structure is shown below:

CR LF I ^ ^ DDD ^ HH:MM:SS ^ DTZ=XX CR LF

where:
CR = Carriage Return

LF = Line Feed
I = Time Sync Status (space, ?, *)
^ = space separator
DDD = Day of Year (001 - 366)
HH = Hours (00-23)
: = Colon separator
MM = Minutes (00-59)
SS = Seconds (00- 60)
D = Daylight Savings Time indicator (S,I,D,O)
TZ = Time Zone
XX = Time Zone offset (00-23)

The leading edge of the first character (CR) marks the on-time point of the data
stream.

The time sync status character I is defined as described below:

(Space) = Whenever the front panel Time Sync lamp is green.
? = When the receiver is unable to track any satellites and the Time

Sync lamp is red.

* = When the receiver time is derived from the battery backed clock

or set manually through the Serial Setup Interface.

The Daylight Saving Time indicator D is defined as:

S = During periods of Standard time for the selected DST schedule.
I = During the 24-hour period preceding the change into DST
D = During periods of Daylight Saving Time for the selected DST

schedule

O = During the 24-hour period preceding the change out of DST

NetClock/GTP Instruction Manual Page 3-13

Section 3: Operation

Example: 271 12:45:36 DTZ=08

The example data stream provides the following information:

Sync Status: Time synchronized to GPS
Date: Day 271
Time: 12:45:36 Pacific Daylight Time

D = DST, Time Zone 08 = Pacific Time

Page 3-14 NetClock/GTP Instruction Manual

Section 3: Operation

3.3.2 Format 1

This format provides the fully decoded time data stream. Format 1 converts the
received day of year data (001-366) to a date consisting of day of week, month,
and day of the month. Format 1 also contains a time sync status character, year,
and time reflecting time zone offset and DST correction when enabled. Format 1
data structure is shown below:

CR LF I ^ WWW ^ DDMMMYY ^ HH:MM:SS CR LF
where:

CR = Carriage Return
LF = Line Feed
I = Time Sync Status (space, ?, *)
^ = space separator
WWW = Day of Week (SUN, MON, TUE, WED, THU, FRI, SAT)
DD = Numerical Day of Month (^1-31)
MMM = Month (JAN, FEB, MAR, APR, MAY, JUN, JUL, AUG, SEP, OCT,

NOV, DEC)
YY = Year without century (99, 00, 01 etc.)
HH = Hours (00-23)
: = Colon separator
MM = Minutes (00-59)
SS = Seconds (00 - 60)
The leading edge of the first character (CR) marks the on-time point of the data

stream.

The time sync status character I is defined as described below:

(Space) = Whenever the front panel Time Sync lamp is green.
? = When the receiver is unable to track any satellites and the Time

Sync lamp is red.
* = When the receiver time is derived from the battery backed clock

or set manually through the Serial Setup Interface.

Example: * FRI 20APR01 12:45:36

The example data stream provides the following information:

Sync Status: The clock is not time synchronized to GPS. Time is derived

from the battery backed clock or set manually
Date: Friday, April 20, 2001
Time: 12:45:36

NetClock/GTP Instruction Manual Page 3-15

Section 3: Operation

3.3.3 Format 2

This format provides a time data stream with millisecond resolution. The Format
2 data stream consists of indicators for time sync status, time quality, leap
second and Daylight Saving Time. Time data reflects UTC time and is in the
24-hour format. Format 2 data structure is shown below:

CR LF IQYY ^ DDD ^ HH:MM:SS.

SSS ^ LD

where:

CR = Carriage Return
LF = Line Feed
I = Time Sync Status (space, ?, *)
Q = Quality Indicator (space, A, B, C, D)
YY = Year without century (99, 00, 01 etc.)
^ = space separator
DDD = Day of Year (001 - 366)
HH = Hours (00-23 UTC time)
: = Colon separator
MM = Minutes (00-59)
SS = Seconds (00-60)
. = Decimal Separator
SSS = Milliseconds (000-999)
L = Leap Second Indicator (space, L)
D = Daylight Saving Time Indicator (S,I,D,O)

The leading edge of the first character (CR) marks the on-time point of the data
stream.

The time sync status character I is defined as described below:

(Space) = Whenever the front panel Time Sync lamp is green.
? = When the receiver is unable to track any satellites and the Time

Sync lamp is red.

* = When the receiver time is derived from the battery backed clock

or set manually through the Serial Setup Interface.

The quality indicator Q provides an inaccuracy estimate of the output data
stream. When the receiver is unable to track any GPS satellites, a timer is
started. Table 3-4 lists the quality indicators and the corresponding error
estimates based upon the GPS receiver 1 PPS stability and the time elapsed
tracking no satellites. The Tracking Zero Satellites timer and the quality indicator
reset when the receiver reacquires a satellite.

Page 3-16 NetClock/GTP Instruction Manual

Section 3: Operation

Inaccuracy

Code

Time Error

(mSec)

Time Since

Unlock (Hours)

Space <1 Locked

A <10 <10

B <100 <100

C <500 <500

D >500 >500

TABLE 3-4 QUALITY INDICATORS

The leap second indicator L is defined as:

(Space) = When a leap second correction is not scheduled for the end of the

month.

L = When a leap second correction is scheduled for the end of the

month.

The Daylight Saving Time indicator D is defined as:

S = During periods of Standard time for the selected DST schedule.
I = During the 24-hour period preceding the change into DST.
D = During periods of Daylight Saving Time for the selected DST

schedule.

O = During the 24-hour period preceding the change out of DST.

Example: ?A01 271 12:45:36.123 S

The example data stream provides the following information:

Sync Status: The clock has lost GPS time sync. The inaccuracy code of “A”

indicates the expected time error is <10 milliseconds.

Date: Day 271 of year 2001.

Time: 12:45:36 UTC time, Standard time is in effect.

NetClock/GTP Instruction Manual Page 3-17

Section 3: Operation

3.3.4 Format 3

Format 3 provides a format identifier, time sync status character, year, month,
day, time with time zone and DST corrections, time difference from UTC,
Standard time/DST indicator, leap second indicator and on-time marker. Format
3 data structure is shown below:

FFFFI^YYYY

MMDD^HHMMSS±HHMMD L # CR LF

where:
FFFF = Format Identifier (0003)
I = Time Sync Status (Space, ? *)
^ = space separator
YYYY = Year (1999, 2000, 2001 etc.)
MM = Month Number (01-12)
DD = Day of the Month (01-31)
HH = Hours (00-23)
MM = Minutes (00-59)
SS = Seconds (00-60)
± = Positive or Negative UTC offset (+,-) Time Difference from UTC
HHMM = UTC Time Difference Hours, Minutes (00:00-23:00)
D = Daylight Saving Time Indicator (S,I,D,O)
L = Leap Second Indicator (space, L)
# = On time point
CR = Carriage Return
LF = Line Feed

The time sync status character I is defined as:

(Space) = Whenever the front panel Time Sync lamp is green.
? = When the receiver is unable to track any satellites and the Time

Sync lamp is red.

* = When the receiver time is derived from the battery backed clock

or set manually through the Serial Setup Interface.

The time difference from UTC, ±HHMM, is selected when the Serial Comm or
Remote port is configured. A time difference of -0500 represents Eastern Time.
UTC is represented by +0000.

The Daylight Saving Time indicator D is defined as:

Page 3-18 NetClock/GTP Instruction Manual

Section 3: Operation

S = During periods of standard time for the selected DST schedule.
I = During the 24-hour period preceding the change into DST.
D = During periods of Daylight Saving Time for the selected DST

schedule.

O = During the 24-hour period preceding the change out of DST.

The leap second indicator L is defined as:
(Space) = When a leap second correction is not scheduled at the end of the

month.

L = When a leap second correction is scheduled at the months end.

Example: 0003 20010415 124536-0500D #

The example data stream provides the following information:

Data Format: 3

Sync Status: Time Synchronized to GPS.

Date: April 15, 2001.

Time: 12:45:36 EDT (Eastern Daylight Time), The time difference

is 5 hours behind UTC.

Leap Second: No leap second is scheduled for this month.

NetClock/GTP Instruction Manual Page 3-19

Section 3: Operation

3.3.5 Format 4

Format 4 provides a format indicator, time sync status character, modified Julian
date, time reflecting UTC with 0.1 millisecond resolution and a leap second
indicator. Format 4 data structure is shown below:

FFFFIMJDXX^HHMMSS.SSSS^L CR LF

where:
FFFF = Format Identifier (0004)
I = Time Sync Status (Space, ? *)
MJDXX = Modified Julian Date
HH = Hours (00-23 UTC time)
MM = Minutes (00-59)
SS.SSSS = Seconds (00.0000-60.0000)
L = Leap Second Indicator (^, L)
CR = Carriage Return
LF = Line Feed

The start bit of the first character marks the on-time point of the data stream.

The time sync status character I is defined as:

(Space) = Whenever the front panel Time Sync lamp is green.
? = When the receiver is unable to track any satellites and the Time

Sync lamp is red.

* = When the receiver time is derived from the battery backed clock

or set manually through the Serial Setup Interface.

The leap second indicator L is defined as:

(Space) = When a leap second correction is not scheduled at the end of the

month.

L = when a leap second correction is scheduled at the months end.

Example: 0004 50085 124536.1942 L
The example data stream provides the following information:

Data format: 4
Sync Status: Time synchronized to GPS.
Modified Julian Date: 50085
Time: 12:45:36.1942 UTC
Leap Second: A leap second is scheduled at the end of the month.

Page 3-20 NetClock/GTP Instruction Manual

Section 3: Operation

3.3.6 Format 90

Format 90 provides a position data stream in NMEA 0183 GPGGA GPS Fix data
format. The Format 90 data structure is shown below:

$GPGGA,HHMMSS.SS,ddmm.mmmm,n,dddmm.mmmm,e,Q,SS,YY.y,+AAAAA.a,M,,,,*CC CR LF

where:
$GP = GPS System Talker
GGA = GPS Fix Data Message
HHMMSS.SS = Latest time of Position Fix, UTC. This field is blank until a

3D fix is acquired
ddmm.mmmm,n = Latitude
dd = degress, 00...90

mm.mmmm = minutes, 00.0000....59.9999

n = direction, N = North, S = South
dddmm.mmmm,e = Longitude
ddd = degress, 000...180

mm.mmmm = minutes, 00.0000....59.9999

e = direction, E = East, W = West
Q = Quality Indicator,
0 = No 3D fix
1 = 3D fix
SS = Number of satellites tracked, 0...8
YY.Y = Dilution of precision, 00.0...99.9
+AAAAA.a,M = Antenna height in meters, referenced to mean sea level
,,,, = Fields for geoidal separation and differential GPS not

supported
cc = Check sum message, HEX 00...7F

Check sum calculated by Xoring all bytes between $

and *.
CR = Carriage Return
LF = Line Feed

NetClock/GTP Instruction Manual Page 3-21

Section 3: Operation

Example:
$GPGAA,151119.00,4307.0241,N,07729.2249,W,1,06,03.2,+00125.5,M,,,,*3F

The example data stream provides the following information:

Time of Position Fix: 15:11:19.00 UTC
Latitude: 43° 07.0241’ North
Longitude: 77° 29.2249’ West
Quality: 3D fix
Satellites Used: 6
Dilution of Precision: 3.2
Antenna Height: +125.5 meters above sea level
Check Sum: 3F

Page 3-22 NetClock/GTP Instruction Manual

Section 3: Operation

3.4 REMOTE OUTPUT USAGE

The Remote Output provide a continuous once-per-second time data stream in
RS-485 levels. RS-485 is a balanced differential transmission, which offers
exceptional noise immunity, long cable runs and multiple loading. These
characteristics make RS-485 ideal for distributing time data throughout a facility.
The Remote Output can drive 32 devices over cable lengths up to 4000 feet.
Spectracom manufactures wall clocks, talking clocks, NTP time providers, RS­485 to RS-232 converters and radio link products that utilize the RS-485 data
stream as an input. Figures 3-8 and 3-9 illustrate typical RS-485 time data bus
interconnections. Follow the guidelines listed below when constructing the RS­485 data bus.

3.4.1 RS-485 Guidelines

Cable selection: Low capacitance, shielded twisted pair cable is recommended
for installations where the RS-485 cable length is expected to exceed 1500 feet.
Table 3-5 suggests some manufacturers and part numbers for extended distance
cables. These cables are specifically designed for RS-422 or RS-485
applications; they have a braided copper shield, nominal impedance of 120
ohms, and a capacitance of 12 to 16 picofarads per foot.

RS-485 cable may be purchased from Spectracom. Specify part number
CW04xxx, where xxx equals the length in feet.

MANUFACTURER PART NUMBER

Belden Wire and Cable Company

9841

1-800-BELDEN-1

Carol Cable Company

C0841

606-572-8000

National Wire and Cable Corp.

D-210-1

232-225-5611

TABLE 3-5 CABLE SOURCES FOR RS-485 LINES OVER 1500 FEET

NetClock/GTP Instruction Manual Page 3-23

Section 3: Operation

For cable runs less than 1500 feet, a lower-cost twisted pair cable may be used.
Refer to Table 3-6 for possible sources.

MANUFACTURER PART NUMBER

Alpha Wire Corporation

5471

1-800-52ALPHA

Belden Wire and Cable Company

9501

1-800-BELDEN-1

Carol Cable Company

C0600

606-572-8000

TABLE 3-6 CABLE SOURCES FOR RS-485 LINES UNDER 1500 FEET

3.4.2 Connection Method

The RS-485 transmission line must be connected in a daisy chain configuration
as shown in Figure 3-8. In a daisy chain configuration, the transmission line
connects from one RS-485 receiver to the next. The transmission line appears
as one continuous line to the RS-485 driver.

A branched or star configuration is not recommended. This method of
connection appears as stubs to the RS-485 transmission line. Stub lengths
affect the bus impedance and capacitive loading which could result in reflections
and signal distortion.

FIGURE 3-8 ONE-WAY BUS INSTALLATION

Page 3-24 NetClock/GTP Instruction Manual

Section 3: Operation

The RS-485 Output can be split in two directions as shown in Figure 3-9. This allows
the NetClock/GTP to be centrally located. Connecting in this method can simplify
installation and possibly reduce the amount of cable required.

FIGURE 3-9 SPLIT BUS CONFIGURATION

Most RS-485 connections found on Spectracom equipment are made using a
removable terminal strip. Wires are secured by a jaw that compresses the wires
when tightened. When using small diameter wire, 22-26 gauge, a strain relief
can be fashioned by wrapping the stripped wire over the insulating jacket as
shown in Figure 3-10. Wrapping the wires in this manner prevents smaller gauge
wires from breaking off when exposed to handling or movement.

NetClock/GTP Instruction Manual Page 3-25

Section 3: Operation

INSULATING JACKET

STRIP

WIRE

WRAP WIRE OVER

INSERT AND

TIGHTEN

FIGURE 3-10 WIRE STRAIN RELIEF

Page 3-26 NetClock/GTP Instruction Manual

Section 3: Operation

The Spectracom Model 8175, TimeView 230, is a display clock with 2.3 inch high
digits. The Model 8177 TimeView 400 features 4.0 inch display digits. TimeView
display clocks use a 6-position terminal block to connect to the RS-485 data bus.
Connect the TimeView to the NetClock/GTP RS-485 Output as shown in Figure
3-11. The TimeView display clocks accept only Data Formats 0 or 1.

FIGURE 3-11 TIMEVIEW RS-485 INTERFACE

The Model 8179T, TimeTap, is an RS-485 to RS-232 converter. The Model
8179T has a DB9 RS-232 interface that receives operational power from the RS­232 flow control pins RTS or DTR. Connect the TimeTap to the RS-485 data bus
as shown in Figure 3-12.

FIGURE 3-12 MODEL 8179T TIMETAP RS-485 INTERFACE

NetClock/GTP Instruction Manual Page 3-27

Section 3: Operation

Spectracom Model 8188 is an Ethernet Time Server that supports NTP and
SNTP time protocols. The Model 8188 accepts either Format 0 or Format 2 and
connects to the RS-485 data bus through a terminal block to DB25 adapter.
Connect the Model 8188 to the NetClock/GTP as shown in Figure 3-13.

FIGURE 3-13 MODEL 8188 RS-485 INTERFACE

The Model 8180 TimeTalk provides an audio time of day announcement to time
stamp voice recorders or for broadcast over radio transmitters. The TimeTalk
accepts only Data Formats 0 or 1. Connect the TimeTalk to the RS-485 time
data bus as shown in Figure 3-14. The synchronizing data stream is input on the
TimeTalk Remote Input connector (DB9 male) and passed through to the
Remote Output connector (DB9 female).

TimeTalk

8 3 9 9 3 8

Input

Remote
Output

1

2

3

Remote

+BDATA

-BDATA

GND

FIGURE 3-14 TIMETALK RS-485 INTERFACE

+BDATA

-BDATA

GND

Page 3-28 NetClock/GTP Instruction Manual

Section 3: Operation

The Model 8185, TimeBurst, provides a digital time-of-day data burst to a radio
transmitter. The TimeBurst, when used with the Spectracom Model 8186
TimeBridge, provides community-wide time synchronization from a single
NetClock/GTP. The TimeBurst accepts only Format 0. Connect the TimeBurst
to the RS-485 data bus using a 3-position terminal block as shown in Figure 3-

15.

FIGURE 3-15 TIMEBURST RS-485 INTERFACE

3.4.3 Termination

A termination resistor is required on devices located at the ends of the RS-485
transmission line. Terminating the cable end preserves data integrity by
preventing signal reflections.

For a one-way bus installation (shown in Figure 3-8), terminate the last device on
the bus. The RS-485 data bus can be split in two directions as shown in
Figure 3-9. In a split bus configuration, terminate the devices installed on each
end of the bus. Most Spectracom products include a built in termination switch to
terminate the RS-485 bus when required.

NetClock/GTP Instruction Manual Page 3-29

SECTION 4: SOFTWARE COMMANDS

4.0 INTRODUCTION

4.1...4.22 RS-232 COMMAND SET

SOFTWARE COMMANDS

4.0 INTRODUCTION

From the rear panel Serial Setup Interface port the user may configure, control and
monitor the NetClock/GTP. Table 4-1 provides a listing of the command set in
alphabetical order. These commands contain a hierarchy of Read, Set and Test
Modes. Figure 4-1 illustrates the command structure. Read Mode is the base level, this
mode the user may only view responses to commands. From Read Mode, the user
may select to enter Test or Set Mode. Set Mode allows the user to not only view
command responses, but configure changes to certain NetClock/GTP functions. Test

Mode allows the user access to special test commands, as well as all Read and Set
Mode commands. After entering Set Mode or Test Mode, the unit will “time out” and
return to Read Mode after 15 minutes of inactivity.

Set Mode On

Set Mode:

Read or Set Standard

Information

FIGURE 4-1 COMMAND STRUCTURE

Set Mode Off

Read Mode:

Read Standard

Information

Test Mode On

Test Mode On

Test Mode Off

Time OutTime Out

Test Mode:

Read or Set Standard
Plus Test Information

NetClock/GPS Instruction Manual Page 4-1

Section 4: Software Commands

COMMAND Description Mode Section

ACD

CONF

DAL

DATE

DEF

DH

DST

FPF

GSS

HELP

IRIG

LOC

LOCK

REMx

RGPS

SERx

SM

Antenna Cable Delay Set 4.1

Display Output Configuration Read 4.2

Display Alarm Log Read 4.3

Date Set 4.4

Set to Factory Defaults Test 4.5

Display Tracking Histogram Read 4.6

Display DST rules Read 4.7

Front Panel Display format Set 4.8

GPS Signal Strength Read 4.9

Help Display Read 4.10

IRIG Output Setup Set 4.11

Location Set 4.12

GPS Lock time-out Set 4.13

Setup Remote Outputs Set 4.14

Reset GPS receiver Test 4.15

Setup Serial Comm Ports Set 4.16

Set Mode 4.17

STAT

SYNC

TIME

TM

VER

Display Status Read 4.18

Time Sync time-out Set 4.19

Time Set 4.20

Test Mode 4.21

Version Read 4.22

TABLE 4-1 ALPHABETICAL LIST OF COMMANDS

Page 4-2 NetClock/GTP Instruction Manual

Section 4: Software Commands

4.1 ANTENNA CABLE DELAY

The command, ACD, reads or sets the antenna cable delay value expressed in
microseconds. The on-time point is offset by the delay value entered to compensate for
antenna cable and in-line amplifier delays. The expected cable and amplifier delays are
typically negligible. The ACD command is intended for advanced user setup. The
advanced user can calculate the delay based upon the cable manufacturer’s
specifications.

Range: 0.000 to 999.999 microseconds
Default Value: 0.000 microseconds
Resolution: 1 nanosecond

To read the antenna cable delay, issue the ACD command as shown below:

Type: ACD <ent>
Response: ANT CABLE DELAY = XXXXXX.XXX MICROSECONDS
Where: XXXXXX.XXX = 000000.000 to 000999.999 microseconds.

To enter a cable delay, place the clock in Set Mode operation, issue the ACD command
as follows:

Type: ACD XXXXXX.XXX <ent>

Where: XXXXXX.XXX = 000000.000 to 000999.999 microseconds.

NOTE: It is not necessary to fill every digit space when entering a
delay value. The delay value can range from 1 to 9 digits long.

The clock then responds with the antenna cable delay value entered.

Example, the calculated cable delay for 140 feet of RG-213 cable is 216 nanoseconds.
Follow the example below to compensate the on-time point by the antenna cable delay.

Type: SM ON <ent>
Response:

SET MODE ON

Type: ACD 0.216 <ent>
Response:

ANT CABLE DELAY = 000000.216 MICROSECONDS

Cable delay can be calculated using the formula:
D = LxC

Where: D = Cable delay in nanoseconds.
V L = Cable length in feet.
C = Constant derived from velocity of light; 1.016.
V = Nominal velocity of propagation expressed as a decimal,

i.e. 66% = .66, value is provided by cable manufacturer.

NetClock/GTP Instruction Manual Page 4-3

Section 4: Software Commands

4.2 DISPLAY OUTPUT CONFIGURATION

The command, CONF, displays the current settings for the clocks outputs. To view the
output configurations, issue the CONF command as shown below:

Type: CONF<ent>

Default response:

FRONT PANEL FORMAT= 24 HOUR
TIME DIFF= +00:00 DST= 0

IRIG FORMAT= FAA
TIME DIFF= +00:00 DST= 0

SERIAL PORT 1
BAUD RATE= 9600 FORMAT #= 00 REQUEST CHAR= T
TIME DIFF= +00:00 DST= 0

SERIAL PORT 2
BAUD RATE= 9600 FORMAT #= 00 REQUEST CHAR= T
TIME DIFF= +00:00 DST= 0

REMOTE PORT 1
BAUD RATE= 9600 FORMAT #= 00
TIME DIFF= +00:00 DST= 0

Page 4-4 NetClock/GTP Instruction Manual

Section 4: Software Commands

4.3 DISPLAY ALARM LOG

The command, DAL, causes the clock to output the alarm history log. Each time a
change in alarm status occurs, an alarm log is created. An alarm log includes the UTC
time and date of the log, event relay status, alarm relay status and lists the conditions
causing the alarms. The alarm log can be displayed a page at a time by adding the
letter P to the command. At the end of each page the option to display more or quit will
be given.

Type: DAL <ent>

- OR ­ DAL P <ent> (paged output)
An example of a paged alarm log is shown below:

TIME = 14:01:03 DATE = 2001-04-12 STATUS CHANGE
ACTIVE ALARMS: MAJOR AND MINOR
FREQUENCY
IN TEST MODE
ADJUST OSCILLATOR
TIME = 14:01:11 DATE = 2001-04-12 STATUS CHANGE
ACTIVE ALARMS: MAJOR AND MINOR
FREQUENCY
IN TEST MODE
TIME = 14:02:13 DATE = 2001-04-12 STATUS CHANGE
ACTIVE ALARMS: MAJOR
FREQUENCY
TIME = 14:03:39 DATE = 2001-04-12 STATUS CHANGE
ACTIVE ALARMS: NONE
MORE <ANY KEY> QUIT <ESC>
TIME = 14:09:50 DATE = 2001-04-12 STATUS CHANGE
ACTIVE ALARMS: MINOR
ANTENNA PROBLEM

END OF LOG

NetClock/GTP Instruction Manual Page 4-5

Section 4: Software Commands

4.4 DATE

The DATE command reads or sets the date of the NetClock/GTP. To retrieve the
current UTC date, issue the DATE command as shown below:

Type: DATE <ent>

Response: DATE = YYYY - MM - DD

Where: YYYY = Year value, 1999, 2000, 2001, etc.
MM = Month value, 01 to 12, 01= January, 04= April
DD = Day of the month, 01 to 31

- = Hyphen

To set the date, place the clock in Set Mode, then issue the DATE command as follows:

Type: DATE YYYY-MM-DD <ent>
Where: YYYY-MM-DD = As defined above.

The clock responds with the date message reflecting the date entered.

NOTE: The date can not be set on clocks tracking GPS satellites.
The set date is overwritten with the received date information.

Example: Set the date for May 9, 2001.

Type: SM ON <ent>
Response: SET MODE ON
Type: DATE 2001-05-09 <ent>
Response:

DATE =2001-05-09

Page 4-6 NetClock/GTP Instruction Manual

Section 4: Software Commands

4.5 RESTORE FACTORY DEFAULTS

The DEF command returns all selectable parameters to the factory default settings.
The clock must be placed in Test Mode to execute the DEF command. The factory
default settings are listed below:

FRONT PANEL FORMAT= 24 HOUR
TIME DIFF= +00:00 DST= 0

IRIG FORMAT= FAA
TIME DIFF= +00:00 DST= 0

SERIAL PORT 1
BAUD RATE= 9600 FORMAT #= 00 REQUEST CHAR= T
TIME DIFF= +00:00 DST= 0

SERIAL PORT 2
BAUD RATE= 9600 FORMAT #= 00 REQUEST CHAR= T
TIME DIFF= +00:00 DST= 0

REMOTE PORT 1
BAUD RATE= 9600 FORMAT #= 00
TIME DIFF= +00:00 DST= 0

LOCK TIME OUT= 00:15:00
SYNC TIME OUT= 02:00:00

To restore the clock to factory default settings enter the following:

Type: TM ON <ent>
Sample response: TIME= 15:31:57 DATE= 2001-04-18 STATUS CHANGE

ACTIVE ALARMS: MAJOR AND MINOR
IN TEST MODE

Type: DEF <ent>
Response:

ALL PARAMETERS SET TO FACTORY DEFAULTS

NetClock/GTP Instruction Manual Page 4-7

Section 4: Software Commands

4.6 DISPLAY TRACKING HISTOGRAM

This command outputs the tracking histogram. The histogram records the number of
qualified satellites tracked each second. At the end of every hour, a log entry is created
and the counters start again. The command responds with the last four hourly entries of
the histogram and current histogram in process. The tracking histogram is useful in
verifying receiver and antenna performance.

Type: DH <ent>

The tracking histogram is output in the following format:

TIME= HH:MM:SS DATE= YYYY-MM-DD QUALIFIED HISTOGRAM

0= XXXXX 1= XXXXX 2= XXXXX 3= XXXXX 4= XXXXX
5= XXXXX 6= XXXXX 7= XXXXX 8= XXXXX Q=QQQQQ

Where: HH:MM:SS = UTC time log was created.
YYYY-MM-DD = Date log was created.
XXXXX = Number of seconds the receiver tracked the

listed quantity of satellites since the beginning
of the hour, 0...3600.

QQQQQ = Number of seconds since the beginning of the

hour the GPS signal was qualified, 0…3600.

Typically, the receiver tracks two to three satellites when using a Model 8228 Window
Mount GPS Antenna. When using the Model 8225 Outdoor antenna, the receiver will
typically track five or more satellites. The NetClock/GTP needs to track only one
qualified satellite to provide accurate and traceable time.

Occasionally, there may be periods when the receiver is unable to track satellites.
When this occurs, the Time Sync alarm count down timer is started. The Sync Alarm
Timer resets whenever the receiver reacquires and qualifies at least one satellite for
one minute. If a receiver is unable to receive and qualify any satellites within the SYNC
alarm period (default is two hours), a Time Sync Alarm is asserted.

Satellites are qualified as valid when the received vehicle ID number is greater than 1
and the satellite is available for Position Fix usage. The qualification count "Q" is
incremented for each second these conditions are met. Typically, the Q value for each
hour should exceed 3000.

Page 4-8 NetClock/GTP Instruction Manual

Section 4: Software Commands

Example: To view the satellite tracking histogram type the following:

Type: DH <ent>
Typical response:

TIME= 16:00:00 DATE= 2001-04-08 QUALIFIED HISTOGRAM

0= 00000 1= 00000 2= 00000 3= 00000 4= 00000
5= 00000 6= 00000 7= 01109 8= 02491 Q= 03600

TIME= 17:00:00 DATE= 2001-04-08 QUALIFIED HISTOGRAM
0= 00000 1= 00000 2= 00000 3= 00000 4= 00000
5= 00000 6= 00414 7= 03186 8= 00000 Q= 03600

TIME= 18:00:00 DATE= 2001-04-08 QUALIFIED HISTOGRAM
0= 00000 1= 00000 2= 00000 3= 00000 4= 00000
5= 00000 6= 00067 7= 02919 8= 00614 Q= 03600

TIME= 19:00:00 DATE= 2001-04-08 QUALIFIED HISTOGRAM

0= 00000 1= 00000 2= 00000 3= 00000 4= 00000
5= 00000 6= 00000 7= 00254 8= 03346 Q= 03600

TIME= 19:18:50 DATE= 2001-04-08 QUALIFIED HISTOGRAM
0= 00000 1= 00000 2= 00000 3= 00000 4= 00000
5= 00000 6= 00000 7= 00000 8= 01130 Q= 01130

END OF LOG

NetClock/GTP Instruction Manual Page 4-9

Section 4: Software Commands

4.7 DAYLIGHT SAVING TIME

Daylight Saving Time corrections can be implemented on the NetClock/GTP display,
IRIG, Serial Comm and Remote Outputs. Each output has a configuration command
that allows selection of a DST rule applied to that output. There are six DST rules to
choose from numbered 1 through 6.

Note: To select always Standard Time place a 0 (zero) in the

command space reserved for the DST rule number.

The factory default rules are as follows:

North America - DST RULE #1

INTO DATE= 1RST SUN APR TIME= 02:00 ADJ= 01:00
OUT-OF DATE= LAST SUN OCT TIME= 02:00

United Kingdom - DST RULE #2

INTO DATE= LAST SUN MAR TIME= 02:00 ADJ= 01:00
OUT-OF DATE= LAST SUN OCT TIME= 02:00

Continental Europe - DST RULE #3

INTO DATE= LAST SUN MAR TIME= 02:00 ADJ= 01:00
OUT-OF DATE= LAST SUN SEP TIME= 02:00

China - DST RULE #4

INTO DATE= 04-12 TIME= 02:00 ADJ= 01:00
OUT-OF DATE= 09-12 TIME= 02:00

Australian 1 - DST RULE #5

INTO DATE= LAST SUN OCT TIME= 02:00 ADJ= 01:00
OUT-OF DATE= LAST SAT MAR TIME= 02:00

Australian 2 - DST RULE #6

INTO DATE= LAST SUN OCT TIME= 02:00 ADJ= 01:00
OUT-OF DATE= 1ST SAT MAR TIME= 02:00

To review the current list of DST rules, issue the DST command as shown below:
Type: DST <ent>

Specific rules can be viewed by adding the DST rule number to the command as shown
below:

Type: DST# <ent>

Where: # = DST rule, 1...6

Page 4-10 NetClock/GTP Instruction Manual

Section 4: Software Commands

Any of the six DST rules can be modified to keep up with changes in DST
implementation. Rules are structured in a week # - day of week - month or a
month - day format.

To change when DST begins (into date), issue the following command:

Type: DSTX IN WWWW DDD MMM HH:MM

HH:MM <ent>

Where: X = Rule number, 1...6
WWWW = Week number, 1rst, 2nd, 3rd, 4th, LAST
DDD = Day of week, SUN, MON, TUE, WED, THU, FRI,

SAT

MMM = Month, JAN, FEB, MAR, APR, JUN, JUL, AUG,

SEP, OCT, NOV, DEC.

HH:MM = Time of change hours:minutes

HH:MM = Amount of change hours:minutes

- OR -

Type: DSTX IN MM DD HH:MM

HH:MM <ent>

Where: X = Rule number, 1...6
MM = Month 01...12
DD = Day of month 01...31
HH:MM = Time change, hours:minutes

HH:MM = Amount of change, hours:minutes

To change when DST ends (out-of date), issue the following command:

Type: DSTX OUT WWWW DDD MMM HH:MM <ent>

Where: X = Rule number, 1...6
WWWW = Week number, 1rst, 2nd, 3rd, 4th, LAST
DDD = Day of week, SUN, MON, TUE, WED, THU, FRI,

SAT

MMM = Month, JAN, FEB, MAR, APR, MAY, JUN, JUL,

AUG, SEP, OCT, NOV, DEC.

HH:MM = Time of change, hours:minutes

- OR -

Type: DSTX OUT MM DD HH:MM <ent>

Where: X = Rule number, 1...6
MM = Month, 01...12
DD = Day of month, 01...31
HH:MM = Time of change hours:minutes

NetClock/GTP Instruction Manual Page 4-11

Section 4: Software Commands

Example: Congress has decided to extend Daylight Saving time by 2 weeks. DST will
now start the last Sunday in March and end on the first Sunday in November. The time
of the change (2:00am), and the amount of the change (1 hour) remains unchanged.

Follow the steps below to implement the new North American DST rule.
Type: SM ON <ent>
Response: SET MODE ON

Type: DST1 IN LAST SUN MAR 02:00 01:00
Response: DST RULE #1

INTO DATE = LAST SUN MAR TIME = 02:00 ADJ = 01:00
OUT-OF-DATE = LAST SUN OCT TIME = 02:00

Type: DST1 OUT 1RST SUN NOV 02:00
Response: DST RULE #1

INTO DATE = LAST SUN MAR TIME = 02:00 ADJ = 01:00
OUT-OF-DATE = 1RST SUN NOV TIME = 02:00

Page 4-12 NetClock/GTP Instruction Manual

Section 4: Software Commands

4.8 FRONT PANEL FORMAT

The command, FPF, reads and sets the front panel display configuration. Display
options include 12 or 24 hour display format, UTC or local time with or without DST
corrections.

To view the current display configuration, issue the FPF command as shown below:

Type: FPF <ent>
Default Response: FRONT PANEL FORMAT= 24 HOUR

TIME DIFF= +00:00 DST= 0

To change the front panel display format, place the clock in Set Mode and issue the

FPF command as follows:

Type: FPF [12:24] [±HH:MM] [#] <ent>

Where: 12 = 12 Hour Display Format

24 = 24 Hour Display Format

±HH:MM = Time Difference from UTC, ±00:00...±12:00; Refer to

Figure 4-2 for UTC time difference map.

# = DST rule number, 0...6.

Where: 0 = No DST, Always Standard Time

1 = North American

2 = United Kingdom
3 = Continental Europe
4 = China
5 = Australian 1
6 = Australian 2

Example, configure the front panel display for 12 hour format, Eastern Time with
Daylight Saving Time.

Type: SM ON <ent>
Response: SET MODE ON
Type: FPF 12 -05:00 1 <ent>
Response:

FRONT PANEL FORMAT = 12 HOUR
TIME DIFF = -05:00 DST = 1

NetClock/GTP Instruction Manual Page 4-13

Section 4: Software Commands

+ 10:00

+ 09:00

+ 08:00

+ 07:00

+ 06:00

+ 11:00

- 11:00

+ 12:00

- 12:00

- 09:00

- 10:00

- 07:00

- 08:00

- 05:00

- 06:00

- 03:00

- 04:00

- 01:00

- 02:00

+ 01:00

+ 00:00

+ 03:00

+ 02:00

+ 04:00

+ 06:00

+ 05:00

FIGURE 4-2 TIME DIFFERENCE MAP

Page 4-14 NetClock/GTP Instruction Manual

Section 4: Software Commands

4.9 GPS SIGNAL STATUS

The GPS Signal Strength command, GSS, provides an indication of receiver operation
and quality of the received GPS signal. This command is useful in verifying proper
antenna placement and receiver performance during installation.

The GSS response provides overall tracking status, position solution and a table
containing individual satellite data.

Issue the GSS command as shown below:

Type: GSS <ent>

Example Response is shown below:

Tracking 3 Satellites
GPS State= 2D-FIX DOP= 04.3
Latitude= N 43 07 01.541 Longitude= W 077 29 15.136 Height= +00102.85 meters
Quality= PASSED
CHAN VID MODE STREN STAT

01 09 08 048 A2

02 00 00 000 00
03 00 00 000 00
04 00 00 000 00
05 00 00 000 00
06 24 08 038 A2
07 02 08 022 A2
08 00 00 000 00

The overall tracking status and position information is presented in the format shown
below:

TRACKING X SATELLITES

GPS STATE= SSSS DOP = 33.3

LATITUDE=[N:S][DD MM SS.SSSS] LONGITUDE=[E:W][DDD MM SS.SSSS] HEIGHT=+HHHH.HH METERS

QUALITY= QQQQQ

Where: X = Number of satellites currently tracking; 0…8.

Typically the window antenna tracks two to three
satellites. The NetClock/GTP requires only one
satellite to provide accurate and traceable time.

NetClock/GTP Instruction Manual Page 4-15

Section 4: Software Commands

SSSS = Fix Mode; SEARCHING, 2D-FIX, 3D-FIX. Searching

is the typical mode when using the window mount
antenna.
2D-FIX is possible if the receiver is tracking at least
three qualified satellites. The receiver latitude and
longitude can be determined from a 2D-Fix.
3D-FIX is possible if the receiver is tracking at least
four qualified satellites. The receiver location and
elevation can be solved from a 3D-Fix.

##.# = Dilution of precision; 00.0…99.9.

This value indicates the degree of uncertainty of a
Position Fix due to the geometry of the satellites used
in the solution. The lower the DOP value, except 00.0,

the lower the degree of uncertainty.
N = North Latitude
S = South Latitude
DDD MM SS.SSS = Latitude Degrees:Minutes:Seconds
E = East Longitude
W = West Longitude
DD MM SS.SSS = Longitude Degrees:Minutes:Seconds

HHHH.HH = Height of GPS antenna expressed in meters. The

height solution is relative to the GPS reference

ellipsoid and not sea level.

QQQQQ = Results of GPS qualification, Passed, Failed. The

GPS signal is considered qualified when at least one

satellite is received having a vehicle ID greater than 1

and is available for Position Fix usage.

NOTE: Position data contained in this response shall

be all zeroes until a 2D-Fix is acquired. Elevation data

is available when a 3D-Fix is acquired.

Page 4-16 NetClock/GTP Instruction Manual

Section 4: Software Commands

Information on each satellite currently being tracking is presented in table form. The
table columns are described below:

CHAN = Channel Number of the GPS receiver, 01...08
VID = Vehicle (satellite) Identification Number, 01...37
MODE = Channel Tracking Mode, 01...08.

Where: 00 - Code Search 05 - Message Sync Detect
01 - Code Acquire 06 - Satellite Time Avail
02 - AGC Set 07 - Ephemeris Acquire
03 - Freq Acquire 08 - Avail for Position
04 - Bit Sync Detect

STREN = Signal strength value relative to SNR, 000... 55. The higher the

number, the greater the received signal.

STAT = Channel status flag. Convert the hexadecimal code word to

binary to find the status flags set.
(MSB) Bit 7: Using for Position Fix
Bit 6: Satellite Momentum Alert Flag
Bit 5: Satellite Anti-Spoof Flag Set
Bit 4: Satellite Reported Unhealthy
Bit 3: Satellite Reported Inaccurate (>16 meters)
Bit 2: Spare
Bit 1: Spare
(LSB) Bit 0: Parity Error

Example: HEX code word A0 translates to the following flags set.
Bit 7: Using for Position Fix

Bit 5: Satellite Anti-Spoof Flag Set

NetClock/GTP Instruction Manual Page 4-17

Section 4: Software Commands

4.10 HELP DISPLAY

The HELP command lists the commonly used commands and command structure.
HELP is available by using the following commands:

Type: HELP <ent>

- OR ­ ? <ent>
Response:

SPECTRACOM CORPORATION NETCLOCK/GTP
COMMAND LIST FOLLOWS (SET MODE MUST BE ON TO CHANGE PARAMETERS)
TIME [HH:MM:SS] = CURRENT UTC TIME
DATE [YYYY-MM-DD] = CURRENT UTC DATE
LOC [D DD MM SS.sss D DDD MM SS.sss] = CURRENT LOCATION
STAT= DISPLAY STATUS INFORMATION
GSS= GPS SIGNAL STRENGTH
CONF= SHOW SETUP INFO FOR ALL OUTPUTS
SERx [BAUD FMT REQ TD DST]= SET UP SERIAL PORT
REMx [BAUD FMT TD DST]= SET UP REMOTE PORT
IRIG [TD DST]= SET UP IRIG
FPF [FMT TD DST]= FRONT PANEL SET UP
LOCK [HH:MM:SS]= GPS LOCK ALARM TIME OUT
SYNC [HH:MM:SS]= TIME SYNC ALARM TIME OUT
DSTx [RULE PARAMETERS] = SET UP DST RULES
EVNT [# CMD PARAM] = SET UP THE EVENT TIMER
ACD [XXXXXX.XXX]= ANTENNA CABLE DELAY
DAL [P] = DISPLAY ALARM LOG
DH [P] = DISPLAY HISTOGRAM LOG
SM [ON:OFF]= SET MODE
FOR FURTHER INFORMATION PLEASE CONSULT YOUR MANUAL

Additional information on the command structure is found by retrieving the command
usage message. To obtain the usage message, type the command followed by a
question mark (?). The IRIG usage message is shown below.

Type: IRIG ?<ent>
Response: USAGE>

IRIG [TD] [DST]

Page 4-18 NetClock/GTP Instruction Manual

Section 4: Software Commands

4.11 IRIG CONFIGURATION

The command, IRIG, reads and sets the IRIG output configuration. IRIG time can be
set for UTC or local time with or with DST corrections. The current IRIG output
configuration can be viewed using the IRIG command as shown below:

Type: IRIG <ent>
Default Response: IRIG FORMAT= FAA

TIME DIFF= +00:00 DST= 0

To change the IRIG output configuration, place the clock in Set Mode and issue the
appropriate IRIG command shown below.

Type: IRIG [TD] [DST] <ent>

Where: TD = Time difference from UTC, ± 00:00...±12:00, refer to

Figure 4-2, UTC Time Difference Map.

DST = DST Rule Number, 0...6.

Where: 0 = No DST, always Standard Time
1 = North America
2 = United Kingdom
3 = Continental Europe
4 = China
5 = Australian 1
6 = Australian 2

Example: Set the IRIG port for Eastern time with automatic DST corrections.

Type: SM ON <ent>
Response: SET MODE ON
Type: IRIG -05:00 1

Response:

IRIG FORMAT = FAA
TIME DIFF = -05:00 DST = 1

NetClock/GTP Instruction Manual Page 4-19

Section 4: Software Commands

4.12 LOCATION

The command, LOC, is for reading or setting the current location of the receiver. This
command displays the current latitude and longitude calculated by the GPS receiver.
During initial installation, time to first fix may be decreased if the user inputs an
approximate position using this command. The GPS receiver constantly calculates its
position based on the satellites it is receiving. Once the unit has acquired its first fix,
entering a new position using this command has no effect. Also, after initial installation
the receiver will keep its current position in Non-Volatile RAM so that on subsequent
power cycles the unit will reach first fix much faster than at initial installation.

To view the current receiver location, issue the LOC command as shown below:

Type: LOC <ent>
Example Response:

To enter a new location place the clock in Set Mode and issue the LOC command as
follows:

CURRENT LOCATION:LATITUDE = N 43 07 00.407 LONGITUDE = W 077 29 13.442

Type: LOC [N:S] [DD MM SS.SSS][E:W] [DDD MM SS.SSS] <ent>

Where: N = North Latitude
S = South Latitude
DD MM SS.SSS = Latitude Degrees:Minutes:Seconds
E = East Longitude
W = West Longitude
DD MM SS.SSS = Longitude Degrees:Minutes:Seconds

Page 4-20 NetClock/GTP Instruction Manual

Section 4: Software Commands

4.13 GPS LOCK TIME OUT

The LOCK command reads or sets the GPS lock time out period. A timer is started
whenever the receiver is not tracking any satellites. The timer is reset when the
receiver reacquires a satellite. A GPS lock alarm is asserted if the receiver fails to
reacquire satellites within the allotted time out period. A GPS Lock alarm actuates the
Minor Alarm relay and removes outputs placed under Lock Signature Control.

To view the current GPS lock time out period issue the LOCK command as shown
below:

Type: LOCK <ent>
Default Response: GPS LOCK TIME OUT= 00:15:00

To change the lock time out value, place the clock in Set Mode and issue the LOCK
command as follows:

Type: LOCK [HH:MM:SS] <ent>

Where: HH:MM:SS = Hours:Minutes:Seconds

NOTE: Due to alarm sequencing, Minor escalating to Major, the
LOCK time out period must be shorter than the SYNC time out
period.

Example: Change the lock time out period to 1 Hour and 30 Minutes.

Type: SM ON <ent>
Response: SET MODE ON
Type: LOCK 01:30:00 <ent>
Response: GPS LOCK TIME OUT= 01:30:00

NetClock/GTP Instruction Manual Page 4-21

Section 4: Software Commands

4.14 REMOTE OUTPUT CONFIGURATION

The command REM 1 reads or sets the configuration of the RS-485 Remote Output.
Remote Output configuration options include: baud rate, data format, UTC or local time
with or without DST corrections.

To view the current Remote Output configurations, issue the command REM1 as shown
below:

Type: REM1 <ent>
Default Response: REMOTE PORT 1

BAUD RATE= 9600 FORMAT #= 00
TIME DIFF= +00:00 DST= 0

To change the Remote Output configuration, place the clock in Set Mode and issue

the REM1 command as follows:

Type: REM1 [BAUD] [FMT] [TD] [DST] <ent>

Where: BAUD = Baud Rate: 1200, 2400, 4800, 9600
FMT = Data Format: 00, 01, 02, 03, 04, 90: Refer to Section

3.3 for a complete description of the data formats
available.

TD = Time Difference from UTC , ±00:00...±12:00; Refer to

Figure 4-2, UTC Time Difference Map.

DST = DST rule number, 0...6.

Where: 0 = No DST, always Standard Time
1 = North America
2 = United Kingdom
3 = Continental Europe
4 = China
5 = Australian 1
6 = Australian 2

Example: Configure the Remote Output port for data format 1, 1200 baud, Mountain

time with DST corrections.

Type: SM ON <ent>
Response: SET MODE ON

Response:

TIME DIFF = -07:00 HOURS DST = 1

Type: REM1 1200 01 -07:00 1 <ent>

BAUD RATE = 1200 FORMAT # = 01

Page 4-22 NetClock/GTP Instruction Manual

Section 4: Software Commands

4.15 RESET GPS RECEIVER

The command, RGPS, completely resets the GPS receiver. This is a radical procedure
and should only be done if the receiver fails to acquire satellites. The RGPS command
returns the receiver to default values. Next, a self-test is performed on the receiver. If
the self-test is successful, a pass message is included in the response. An
unsuccessful self-test will provide a numeric code in the self-test status message. The
entire process takes about 10-12 seconds. At this point, the receiver will perform as if it
has just arrived from the factory. It may take 20 to 30 minutes to achieve first fix. This
command is only available in Test Mode. To issue a GPS reset, follow the example
below:

Type: TM ON <ent>
Response:

TIME = 20:42:11 DATE = 2001-04-21

Type: RGPS <ent>
Response: TIME= 20:42:32 DATE= 2001-04-21 RESET GPS RECEIVER

SELF-TEST= PASS

TEST MODE ON

- OR -

ACTIVE ALARMS: MAJOR AND MINOR
IN TEST MODE

NetClock/GTP Instruction Manual Page 4-23

Section 4: Software Commands

4.16 SERIAL COMM CONFIGURATION

The commands, SER1 and SER2, read or set the configuration of the Serial Comm
outputs. Serial Comm configuration options include baud rate, data format, request
character, UTC or local time with or without DST corrections.

To view the current Serial Comm configurations issue the SERx command as shown
below:

Type: SERX <ent>
Default Response: SERIAL PORT x

BAUD RATE = 9600 FORMAT# = 00 REQUEST CHAR = T
TIME DIFF = +00:00 DST = 0

Where: X = Serial Comm Number 1, 2

To change a Serial Comm port configuration, place the clock in Set Mode and issue the
SERx command as follows:

Type: SERX [BAUD] [FMT] [REQ] [TD] [DST] <ent>

Where: X = Serial Comm Number 1,2
BAUD = Baud Rate: 1200, 2400, 4800, 9600
FMT = Data Format: 00, 01, 02, 03, 04, 90: Refer to Section

3.3 for a complete description of the data formats
available.

REQ = Request Character. Any symbol, number or

uppercase letter can be configured as the request
character. The Serial Comm port will output the
selected data format upon receiving this character.
The Serial Comm port can also be configured to output
continuously once-per-second by typing the word
NONE as the request character.

TD = Time Difference from UTC, ±00:00...±12:00; Refer to

Figure 4-2, UTC Time Difference Map.

DST = DST rule number, 0...6.

Where: 0 = No DST, always Standard Time
1 = North America
2 = United Kingdom
3 = Continental Europe
4 = China
5 = Australian 1
6 = Australian 2

Page 4-24 NetClock/GTP Instruction Manual

Section 4: Software Commands

NOTES: A once-per-second output is enabled when the request
character is set for NONE.
The time contained in data formats 02, 04, and 90 always reflect
UTC time. The time difference parameter in the Serial Comm
configuration command has no effect on output time.

Example: Configure Serial Comm 1 to respond with data format 03 whenever a ? is

received. Set the bit rate at 4800 Baud and time reflecting Pacific
Standard time (no DST corrections).

Type: SM ON <ent>
Response:

Type: SER1 4800 03 ? -08:00 0 <ent>

SET MODE ON

Response: SERIAL PORT 1

BAUD RATE = 4800 FORMAT # = 03 REQUEST CHAR = ?

TIME DIFF = -08:00 DST = 0

NetClock/GTP Instruction Manual Page 4-25

Section 4: Software Commands

4.17 SET MODE

This command is used to read or enter Set Mode operation. As a safeguard, the unit
must be placed into Set Mode whenever operational parameters are entered. The unit
“times out” of Set Mode and returns to Read Mode operations if no commands are
issued for 15 minutes. To read the Set Mode status ( ON or OFF), issue the SM
command as shown below:

Type: SM <ent>
Response: SET MODE ON

or
SET MODE OFF

To place the unit into Set Mode:

Type: SM ON <ent>
Response: SET MODE ON

To return the unit to Read Mode:

Type: SM OFF <ent>
Response: SET MODE OFF

Page 4-26 NetClock/GTP Instruction Manual

Section 4: Software Commands

4.18 STATUS COMMAND

The STAT command provides the current UTC time and date, Time Sync status, GPS
Lock status, time remaining in GPS Lock and Time Sync timers and Oscillator Lock
status.

To retrieve the operational status, issue the STAT command as follows:

Type: STAT <ent>
The sample response below is from a clock currently Time Synchronized and receiving

a qualified GPS signal:

TIME= 18:29:44 DATE= 2000-05-05
TIME SYNC STATUS= OK GPS LOCK STATUS= OK
GPS SIGNAL= QUALIFIED
OSCILLATOR STATUS= LOCKED

The response below is from a clock that is currently not receiving any qualified
satellites. Note that the GPS Lock and Time Sync Alarm count down timers have
started but no alarms are yet asserted.

TIME= 18:47:51 DATE= 2000-05-05
TIME SYNC STATUS= OK GPS LOCK STATUS= OK
GPS SIGNAL= NOT QUALIFIED
TIME REMAINING: GPS LOCK= 00:10:53 TIME SYNC= 01:55:53
OSCILLATOR STATUS= LOCKED

The response below is from a clock that has lost GPS Lock and Time Sync. Note that
both counters have expired and a GPS Lock and Time Sync has changed to “NONE”.
The Oscillator Status is changed to “Not Locked” whenever a loss of Time Sync occurs.

TIME= 20:37:41 DATE= 2000-05-05
TIME SYNC STATUS= NONE GPS LOCK STATUS= NONE
GPS SIGNAL= NOT QUALIFIED
TIME REMAINING: GPS LOCK= 00:00:00 TIME SYNC= 00:00:00
OSCILLATOR STATUS= NOT LOCKED

NetClock/GTP Instruction Manual Page 4-27

Section 4: Software Commands

4.19 SYNC TIME OUT

The SYNC command reads or sets the Sync Time Out period. A timer is started
whenever the receiver is not tracking any satellites. The timer is reset when the
receiver reacquires a satellite. A Time Sync Alarm is asserted if the receiver fails to
reacquire satellites within the allotted time out period. A Time Sync Alarm causes a
Major Alarm and removes outputs placed under SYNC Signature Control. To view the
current sync time out period, issue the SYNC command as shown below:

Type: SYNC <ent>
Default Response: TIME SYNC TIME OUT= 02:00:00

To change the sync time out value, place the clock in Set Mode and issue the SYNC
command as follows:

Type: SYNC HH:MM:SS <ent>
Where: HH:MM:SS = Hours:Minutes:Seconds

NOTE: Due to alarm sequencing, Minor elevating to Major, the
SYNC time out period must be longer than the LOCK time out
period.

Example: Change the SYNC time out period to 8 hours.

Type: SM ON <ent>
Response: SET MODE ON

Type: SYNC 08:00:00 <ent>

Response: TIME SYNC TIME OUT= 08:00:00

Page 4-28 NetClock/GTP Instruction Manual

Section 4: Software Commands

4.20 TIME

The command, TIME, reads or sets the time of the NetClock/GTP.

To retrieve the current UTC time, issue the TIME command as shown below:

Type: TIME <ent>

Response: TIME = HH:MM:SS
Where: HH = UTC hours 00...23
MM = Minutes 00...59
SS = Seconds 00...60

To set the time, place the clock in Set Mode and issue the TIME command as follows:

Type: TIME HH:MM:SS <ent>

Where: HH:MM:SS = As defined above.
Response: Time message reflecting the time entered.

NOTE: Clocks tracking GPS satellites can not be set using this
command. The received time data overwrites the set time.

Example: Manually set the TIME 13:45:00.

Type: SM ON <ent>
Response: SET MODE ON

Type: TIME 13:45:00 <ent>

Response: TIME = 13:45:00

NetClock/GTP Instruction Manual Page 4-29

Section 4: Software Commands

4.21 TEST MODE

This command is used to read or enter Test Mode operation. Test Mode commands are
used in factory testing and field troubleshooting. The unit “times out” of Test Mode and
returns to Read Mode if no commands are issued for 15 minutes. Major and Minor
alarms are asserted whenever the clock is in Test Mode.

To read the Test Mode status (ON or OFF), issue the TM command as shown below:

Type: TM <ent>
Response: TEST MODE ON

- OR -

TEST MODE OFF

To place the clock into Test Mode operation, issue the TM command as follows:

Type: TM ON <ent>
Response: TIME = HH:MM:SS DATE = YYYY-MM-DD STATUS CHANGE

ACTIVE ALARMS: MAJOR AND MINOR
IN TEST MODE

- OR -

TEST MODE ON

Page 4-30 NetClock/GTP Instruction Manual

Section 4: Software Commands

4.22 VERSION COMMAND

This command provides all the software version levels of the programs contained in the
clock. The time and date the unit was first powered ON is recorded. To retrieve version
information, issue the VER command as shown below:

Type: VER <ent>
Example Response:

Spectracom Corporation NetClock/GTP Model 8183A
Software Version 1.0.0 Date: May 18, 2001 09:14:48
Unit Started 20:42:39 2001-05-15
Front Panel Version 2.00
IRIG Version 9.01
Serial Port 1 Version 2.03
Serial Port 2 Version 2.03
Remote Port 1 Version 2.03
GPS Receiver = 8 Channel GT Version 2

NetClock/GTP Instruction Manual Page 4-31

SECTION 5: SERVICE INFORMATION

5.0 INTRODUCTION

5.1 RECEPTION TROUBLESHOOTING

5.2 TCXO ADJUSTMENT

SERVICE INFORMATION

5.0 INTRODUCTION

This section provides information on troubleshooting GPS reception problems
and instructions for adjusting the TCXO oscillator.

5.1 RECEPTION TROUBLESHOOTING

Please review this section prior to calling the Spectracom Customer Service
Department. If the reception problem can not be solved by following the
guidelines outlined in this section, please call for Customer Service at
585-321-5800.

5.1.1 No Reception

Cable or connector problem: Measure the antenna cable resistance to verify

the integrity of the cable and connectors. Remove the antenna cable from the
rear panel of the receiver and measure the resistance from the coax center to
shield. Refer to Table 5-1 for typical resistance values of the antenna and inline
amplifier alone and when combined.

DEVICE DESCRIPTION RESISTANCE

8225 Outdoor Antenna 180 ohms

8227 In-line Amplifier 165 ohms

8225 and 8227 Antenna/Amplifier 85 ohms

TABLE 5-1 TYPICAL ANTENNA CABLE RESISTANCE VALUES

Failed impulse suppressor: The Model 8226 provides lightning protection
when the outdoor GPS antenna is used. The Model 8226 has a high impedance
when measuring from the center conductor to ground and a low throughput
resistance. A failing impulse suppressor may be tripping prematurely. The
easiest way to test the Model 8226 is to temporarily replace it with a Type N
barrel connector. If the receiver begins tracking satellites within 20 minutes, the
impulse suppressor has failed and must be replaced.

Cable length: Excessively long or improper cable type may prevent the receiver
from tracking satellites. Refer to Section 2.2 for cable recommendations when
using the Model 8225 GPS Antenna

Antenna location: The antenna must have a good view of the sky. Refer to
Section 2.1 for antenna location guidelines.

NetClock/GTP Instruction Manual Page 5-1

Section 5: Service Information

GPS reset: In rare occasions, the GPS receiver may require a reset to set the

receiver to default values. The receiver must be placed in Test Mode to issue
the GPS Reset command. Issue the GPS Reset command, RGPS, as shown
below:

Type: TM ON <ent>

The unit will respond with a message stating Test Mode has been enabled.
During Test Mode operation, the Major and Minor alarms are asserted.

Type: RGPS <ent>

After an approximate 10 second delay, the receiver responds with a reset status
message. Allow 20 minutes for the receiver to begin tracking satellites.

Receiver location: Setting the current receiver position may assist in obtaining
a satellite fix. To enter a new location, place the clock in Set Mode and issue the
LOC command as follows:

Type: SM ON <ent>

Response: SET MODE = ON

Type: LOC [N:S] [DD MM SS.SSS][E:W] [DD MM SSS.SSS]<ent>

where: N = North Latitude
S = South Latitude
DD MM SS.SSS = Latitude Degrees:Minutes:Seconds
E = East Longitude
W = West Longitude
DDD MM SS.SSS = Longitude Degrees:Minutes:Seconds

NOTE: The approximate location is adequate, zeros
may be used for the seconds values.

Allow 20 minutes for the receiver to begin tracking satellites.

5.1.2 Low GPS Quality

Cable Length: Excessively long or improper cable type may cause low GPS

quality due to cable attenuation. Long GPS antenna lengths may require an
inline amplifier or lower loss cable. Refer to Section 2.2 for GPS cable
recommendations and Section 2.4 for inline amplifier information when using the
Model 8225 Antenna

Antenna location: The antenna must have a view of the sky with views to the
horizon. Nearby obstructions can reduce the receiver's ability to track the
maximum number of satellites available.

Local Interference: Another reason for poor reception is harmonics from a
local broadcast interfering with the GPS L1 carrier of 1575.42 MHz. Certain
television or FM radio broadcasts, while operating within their frequency
allocation, can cause GPS jamming due to harmonics of the carrier. Television

Page 5-2 NetClock/GTP Instruction Manual

Section 5: Service Information

interference presents a greater challenge due to higher output power, typically 2­3 MW. Table 5-2 lists the potentially problem television stations and their
respective GPS harmonic.

CHANNEL HARMONIC

66 2nd

23 3rd

10 8th

7 9th

6 18th & 19th

5 20th

TABLE 5-2 TELEVISION STATIONS WITH GPS JAMMING POTENTIAL

FM radio stations, while lower in radiated power, can cause GPS jamming also.
Table 5-3 lists the potentially problem radio frequencies and their respective GPS
harmonic.

FREQUENCY HARMONIC

104.8 - 105.2 15th

98.3 - 98.7 16th

92.5 - 92.9 17th

87.3 - 87.7 18th

TABLE 5-3 FM RADIO FREQUENCIES WITH GPS JAMMING POTENTIAL

If relocating the antenna away from the interfering source does not solve the
problem or if relocation is not possible contact Spectracom Tech Support for
assistance.

NetClock/GTP Instruction Manual Page 5-3

Section 5: Service Information

5.2 OSCILLATOR ADJUSTMENT

Over time the NetClock/GTP TCXO oscillator may require an adjustment to
compensate for crystal aging. The NetClock/GTP warns when this adjustment is
needed by asserting an Adjust Oscillator Alarm. This condition causes the front
panel display to flash all 8’s every three seconds and activates the Minor Alarm
relay. An Adjust Oscillator Alarm is asserted when the frequency controlling D/A
converter approaches a control range limit. Typically, this alarm provides a two
to three month warning before a control range end is reached.

On rare occasions, an oscillator may experience a sudden shift in frequency,
causing an Adjust Oscillator and a Frequency Alarm. When this occurs, both
Major and Minor alarms are activated. The D/A is set to a control range end
unable to correct the oscillator frequency. Frequency error shall exceed 1 x 10-7

This section describes the oscillator adjustment procedure using a frequency
counter and an RS-232 terminal. The frequency counter must have a time base
accuracy and measurement resolution of at least 1 x 10-7 (1.0 Hz at 10 MHz).

A PC running terminal emulation software (HyperTerminal, ProComm Plus, etc.)
can be used as an RS-232 terminal. Configure the terminal for ANSI emulation,
9600 baud and a character structure of 1 start, 8 data, 1 stop and no parity. Flow
control is not required, although XON/XOFF is supported.

5.2.1 Adjustment Procedure

Perform the steps listed below to adjust the TCXO oscillator.

1. If the unit is rack mounted, remove it from the rack.

2. Disconnect the GPS antenna.

3. Remove the top cover.

4. Connect the terminal to the Serial Setup Interface port.

5. Place the NetClock/GTP in Test Mode by sending the TM command as
follows:

Type: TM ON <ent>

Response: TIME= 19:22:03 DATE= 2001-04-08 STATUS CHANGE

ACTIVE ALARMS: MAJOR AND MINOR
IN TEST MODE
ADJUST OSCILLATOR

6. Set the D/A to the center of it’s control range by setting the D/A to 8000 as
shown below:
Type: DA 8000<ent>

Page 5-4 NetClock/GTP Instruction Manual