Model 1084B/C GPS Satellite Clock (40 ns)

Model 1084B/C GPS Satellite Clock (40 ns)

Value driven version of Model 1088B, featuring the same high accuracy, reliability and many of the same feature-extending options.

Model 1084A/B/C User Manual
Download PDF(4 MB) »

Model 1084B/C Quick Setup Guide
Download PDF(593 kB) »

Model 1084A/B/C User Manual Español
Download PDF(1017 kB) »

Model 1084B/C Data Sheet
Download PDF(2 MB) »

Model 1084A/B/C Data Sheet Español
Download PDF(501 kB) »

GPS Antenna Data Sheet
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Focused on high performance and maximum value, the Model 1084B/C delivers many of the same high end performance, features and flexibility of the 1088B precision time clock, but at lower cost.

Three BNC connectors deliver several output options supporting IRIG-B modulated, and various combinations of IRIG-B unmodulated, Programmable Pulse (supporting multiple output modes) and 1 PPS. All are high drive outputs capable of driving multiple loads wired in parallel.

Like the 1088B but with a single option slot, Model 1084B/C supports options for an internal Network Time Protocol (NTP), four configurable fiber optic outputs, COMTRADE Sample Rate Generator, Power System Time, Frequency and Phase Monitor, a second RS-232 port and more.

Model 1084B/C is available with three front panel configurations. See Key Features for more information.

  • Highest accuracy, < ± 40 ns typical; < ± 100 ns worst case
  • Three BNC connectors (optional terminal strip connector available)
  • Optional Fiber Optic support
  • NTP compatible
  • Two Form C (SPDT) fail-safe relays, locked and jumper selectable
  • Event input support

Versions B/C offer various interface options (see photos):

  • 1084B has four LEDs to monitor operating status, an LCD display and keypad, providing easy access to setup and system status information.
  • 1084C includes the 1084B features and adds a a large LED time display.
  • IEEE C37.118.1-2005 compliant for Synchrophasor use.

Receiver Characteristics

Timing Accuracy

Accuracy Note

Specifications apply at the 1 PPS output, in the presence of Selective Availability (SA), as of date of publication.

Accuracy UTC/USNO

± 100 ns rms, 1 PPS output


< ± 40 ns rms, in Position-Hold Mode


  • CMOS output signals are synchronized to the 1 PPS output, ± 50 ns, maximum.
  • IRIG-B modulated, ± 1 µs, maximum
  • The leading edge of the start bit of a received RS-232 data message may be selected to trigger the Event A input, providing synchronization with 100 ns resolution.

Position Accuracy

10 meters, rms, 90 % confidence

Satellite Tracking

Twelve (12) channel, C/A code (1575.42 MHz). Receiver simultaneously tracks up to twelve satellites. Results from all tracked satellites are averaged in Position-Hold Mode or, with Position-Hold Mode off, using least-squares estimation.


  • 150 seconds typical, cold start
  • 15 minutes, 90 % confidence, cold start
  • 40 seconds, with almanac less than 1 month old
  • 15 seconds, with ephemeris less than 4 hours old

The GPS Data Backup Battery is included in all Model 1084s. This feature improves acquisition time by supplying constant power to the real-time clock and RAM in the GPS receiver module.



DCXO, 1x10-7, unlocked

Allan Variance

(locked to GPS, in Position-Hold Mode)

1 second: 5x10-10 (2x10-10, typical)
1 day: 5x10-13

I/O Configuration

Output Connectors

Three BNC, one IRIG-B Modulated and two user-configurable:

  • IRIG-B Modulated, bus driver, 4 Vpp, 20 ohms source impedance, drives a 50-ohm load at 3 Vpp
  • IRIG-B unmodulated or Programmable Pulse; jumper-selectable
  • 1 PPS, IRIG-B unmodulated or IRIG-B modified Manchester; jumper-selectable

Jumper-selectable outputs are 5 V CMOS bus drivers with 10 ohms source impedance and ± 75 mA drive capability.

Event Inputs

Event A Input:

One input is available as an alternate function, with a simple hardware modification to the 1 PPS configurable output. The input may be configured to accept an external 1 PPS signal, and measure the deviation from 1 PPS/GPS with 100 ns resolution. Each input may also be configured to record up to 500 sequential events with 100 ns resolution, provided that the events are separated by 11 ms. Event data is stored in battery-backed RAM.

Programmable Pulse Output

Four modes:

  • Every 1 second to 60,000 seconds, starts top of the minute
  • Hourly at a specified offset
  • Daily at a specified time of day
  • One-shot at a specified time of year

Pulse duration is programmable from 0.01 seconds to 600 seconds, except in one-shot mode, where the output is Low prior to the specified time and High thereafter.

Relay Contacts

Two (2) sets, Form C (SPDT) fail-safe, 0.3A at 130 Vdc; one is Locked function; the second one is jumper-selectable and may be Fault, 1 PPH, or Programmable Pulse



  • 2 character x 20 character supertwist LCD - (Models 1084B/C only)
  • 20 mm (0.8 in) LED; 9 digits - (Model 1084C only)

  • Time: UTC or local
  • Position: latitude, longitude, altitude
  • Receiver and clock status
  • 1 PPS (input) deviation
  • Event time

Status LEDs
  • Operate (green)
  • On Line (green)
  • Unlocked (red)
  • Fault (red)

Eight keys (Models 1084B/C only)

  • Local time offset
  • Output code select: Local/UTC
  • Recorder output A
  • Daylight Saving Time: On/Off/Automatic
  • Backlight control: On/Off/Automatic
  • Event input: Event/1 PPS
  • Programmable Pulse setup
  • Antenna delay
  • Clock offset
  • Out-of-Lock time: 1 minute to 99 minutes, Off, or Zero Delay
  • Auto-Survey: On/Off, Survey duration
  • Position Hold: On/Off, Position Auto/Manual
  • Option Configuration and Setup
  • Serial port: RS-232


  • 1200 baud to 19,200 baud; 7 or 8 data bits; 1 or 2 stop bits; even/odd/no parity
  • Broadcast modes include ASCII, Extended ASCII, ASCII with Time Quality, and Vorne (output once every second), Status (output onchange of Status) and Event (outputon an Event)
  • Male 9-pin D-sub; Second port available (order number 1084opt19)

Transmit Only

Power Requirements



(Option 07) 85 Vac to 264 Vac, 47 Hz to 440 Hz, 20 VA maximum or 110 Vdc to 370 Vdc, 15 W maximum


(Option 07) IEC-320 with fuse and mating cordset. Specify option P01 - P10

Available cordset plug style and specifications are described in the Options and Accessories section.




1 RU rack mount or tabletop, 260 mm deep FMS, Rack mounts included.
635 mm x 381 mm x 229 mm (25 in x 15 in x 9 in), shipping


2 kg (4.5 lbs), net
5.5 kg (12 lbs), shipping


0.75 in pipe (1 in - 14 marine) thread

Cable Connection: F-type
Size: 80 mm hex (across flats) x 84 mm tall (3.2 in x 3.3 in), including connector
Weight: 170 g (6 oz)

Antenna Cable

Type: RG-6, 15 m (50 ft) provided
Weight: 0.69 kg (1.52 lbs) per 15 m

Antenna Mounting

0.75 in pipe (1 in - 14 marine) thread



Operating: 0 °C to + 50 °C (- 20 °C to + 70 °C typical)
Nonoperating: - 40 °C to + 75 °C




Radiated susceptibility: passes walkie-talkie test.

Conducted emissions: power supply complies with FCC 20780, Class A and VDE 0871/6.78 Class A.

Surge withstand capability (SWC), power inlet: designed to meet ANSI/IEEE C37.90-1 and IEC 801-4

Certificates and Approvals

CE mark/label and certificate

Except as noted otherwise, only one I/O Option may be installed. Click on the Option of interest for more information.

1084opt06 Parallel BCD Output, 1 ms Resolution
1084opt17 Parallel BCD with Second RS-232 Port
1084opt19 1 Second RS-232 Port
1084opt20 2 Fiber-Optic, Type ST 820 nm
1084opt20A Four Configurable Fiber-Optic Outputs
1084opt23 COMTRADE Sample Rate Generator
1084opt27 8-Channel High Drive IRIG-B Output
1084opt28 Power System Time, Frequency, and Phase Monitor
1084opt29 Four Additional Outputs with Dry Contact and + 25/50 Vdc
1084opt34 Network Time Protocol (NTP) / Precision Time Protocol (PTP) Server
1084opt36 Four Configurable Outputs
1084opt01 LCD Backlight
1084opt04 On/Off Switch (1084B/1093B)
1084opt07 IEC-320 Power Inlet 85 Vac to 264 Vac RMS, 110 Vdc to 370 Vdc
1084opt08 10 Vdc to 60 Vdc Terminal Power Strip and Surge Withstand
1084opt10 85 Vac to 250 Vac RMS, 110 Vdc to 350 Vdc Terminal Power Strip and Surge Withstand

1 May be combined with other I/O options that do not include an additional RS-232 port
2 May be combined with other I/O options

AS0028200 19 Inch Rack Mount Kit
AS0087800 Arbiter GPS Active Timing Antenna
CA0021315 1 15 m (50 ft) RG-6 Antenna Cable, RoHS
P01 - P10 2 Country specific power cord with straight female end
PD0052500 Quick Setup Guide (1084)
AP0003400 3 BNC (Male) Breakout to 100 mm Wires
AP0007700 4 Modular DB-9 to RJ-11 Adapter, Preconfigured
AP0008900 3 BNC (Female) Breakout to 100 mm Wires
AP0013400 GPS Antenna Cable Splitter, F-Type, 950-2150 MHz, One Port Pass DC
AP0014900 3 BNC (Female) Breakout to Screw Terminal
AP0015000 3 BNC (Male) Breakout to Screw Terminal
AS0031000 Operation Manual (1084)
AS0033100 Rack Slide Kit
AS0044600 Antenna Mounting Kit
AS0044700 5 21 dB In-Line Pre-amplifier
AS0048900 Antenna Grounding Block Kit, RoHS
AS0056600 24 Inch Rack Mount Kit
AS0067200 4 Programming Port Cable with adapter
AS0094500 GNSS Surge Protector
CA0019806 RS-232 Null Modem Cable, DB9F-DB9F, 2 m (6 ft) length
CA0021302 1 2 m (6 ft) RG-6 Antenna Cable, RoHS
CA0021306 1 6 m (20 ft) RG-6 Antenna Cable, RoHS
CA0021330 1 30 m (100 ft) RG-6 Antenna Cable, RoHS
CA0021345 1 45 m (150 ft) RG-6 Antenna Cable, RoHS
CA0021360 1 60 m (200 ft) RG-6 Antenna Cable, RoHS
CA0021375 1 75 m (250 ft) RG-6 Antenna Cable, RoHS
CA0022500 6 Option 28 System Frequency Reference Cable, 6 m (20 ft)
CA0023600 4 RJ-11 Cable Four-Pin Crossed, 2 m (7 ft)
CA0026000 7 Power Cord IEC-320 to Bare Leads
CN0010550 8 50-Pin Parallel BCD Mating Connector
CN0027800 Type F, Male, RG-11 Antenna Cable Crimp-on Connector
CN0050700 Type F, Male, RG-6 Antenna Cable Compression Connector, RoHS
CN0050800 9 Type F, Male, RG-6 Plenum Rated Antenna Cable Compression Connector, RoHS
TF0006000 Type F, RG-11 Antenna Cable Crimp Tool
TF0013200 Antenna Cable Stripping Tool, RG-6
TF0013300 Antenna Cable Stripping Tool, RG-11
TF0024000 Type F, RG-6 Antenna Cable Compression Tool
WC0004900 1 300 m (1000 ft) Roll RG-11 Cable
WC0005000 1 300 m (1000 ft) Roll RG-6 Cable
WC0005200 10 300 m (1000 ft) Roll RG-6 Plenum Rated Cable

1 Stocked length. Custom lengths available from 0.3 m (1 ft) to 300 m (1000 ft). Contact factory.
2 Only applies if Power Option 07 is ordered
3 Converts pair of wires to BNC.
4 Used with retired options: Option 32 or Option 33.
5 Used for cable lengths greater than: RG-6 75 m (250 ft) ; RG-11 120 m (400 ft)
6 Used with Option 28.
7 Used with Option 07.
8 Used with Option 06.
9 Indoor use only. Not weather resistant. Not UV radiation protected.
10 Stocked length. Custom lengths available from 0.3 m (1 ft) to 300 m (1000 ft). Contact factory. Indoor use only. Not weather resistant. Not UV radiation protected.

Click to Download Latest Version of Software
Arbiter Time Service_01Jan2010_1500 PC Clock Synchronization Service for WIN NT/2000/XP/Vista/7. Not compatible with WIN 8.
Tera Term_01Jan2010_23 This is a very good HyperTerminal replacement. Able to capture data from Models 930A and 931A. Also able to program the GPS Satellite Controlled Clocks via serial commands.
TimeRC_3.0 NTP Server Test Utility. Screen Capture Utility.


Software Version and Related Information

Arbiter Time Service Tool (Arbiter Time Service)

PC Clock Synchronization Service for WIN NT/2000/XP/Vista/7. Not compatible with WIN 8. The Arbiter Time Service installs on Microsoft® Windows NT/2000/XP and runs as a service to keep the PC clock synchronized to an Arbiter GPS clock. The Arbiter Time Service connects with an RS-232 cable and interrogates the clock for the time signal

VersionRev LevelVersion Notes

Terminal Emulation Program (Tera Term)

Free software terminal emulator (communications program) for Microsoft Windows.

  • Tera Term (Pro) is a free software terminal emulator (communication program) for MS-Windows.
  • Supports VT100 emulation, telnet connection, serial port connection, etc.
  • Compatible with Windows 98, Windows NT, Windows 2000, Windows XP, Vista, Windows 7


Used as a test tool for NTP servers, synchronizes computer time over a network. Also used to save screen captures from the Model 930A, Model 931A, and Model 933A.

VersionRev LevelVersion Notes
Firmware Information (EPROM based firmware is not available for download)
1084_Firmware_21Mar2017 Requires an EPROM update from Arbiter.
NTP/PTP Firmware_2.08_update-00.10 Downloadable. UNZIP, read instructions, and use the web/SSH interface to import apf file(s) into unit.
Power System Time, Frequency, and Phase Monitor Firmware_05Apr2012 Requires an EPROM update from Arbiter.


Firmware Version and Related Information

EPROM Update (1084_Firmware)

VersionRev LevelVersion Notes

Updates are not security related.

  1. Fixed serial output menu to correctly integrate settings for the Option 28 Power System Time, Frequency, and Phase Monitor.
  2. Added serial command to enable/disable the vernier circuit data. This allows more control over the internal time keeping mechanisms.

Updates are not security related.

  1. Fixed the overlap of the serial commands to set the longitude and configure the event index.

Updates are not security related.

  1. Fix leap second operation to properly warn and implement the leap second.
  2. Changed the IRIG-B Daylight Saving Time (DST) pending bit to change state at xx:59:01 (was starting at xx:59:00). Now it is consistent with Leap Second Pending bit operation.
  1. Baseline code alignment with other legacy clock models. Does not affect clock operation at the outputs (BZ734).
  1. DST stop error. Not exiting DST mode properly when "day of week" value matches the first day of the following month (BZ733). Example: DST will not properly stop if DST stop was set to Last Sunday of October and November 1 is also on a Sunday.
  2. Add Option 36 as a Slot B selection

Option 34 and Option 35 updates:

  1. PTP enable/disable now shows on front panel display.
  2. Enabled leap second flags, leap second application time (seconds of year), and UTC-GPS seconds offset.
  3. Fixed formatting related to the version strings.
  1. Event Input: Add legacy support for "xxxA" command response. Can select "Index not active" or "NO DATA" using the new "nRT" command. (BZ 687)
  1. Fixed Event Input where the start index was not properly set after events were erased. This is related to the new "EN" command that starts the event count at zero or one.
  1. Added the ability to count events starting from zero (0) or one (1). Controlled by "EN" serial command. Default configuration will be 0.
  1. Update to time quality functionality. Time quality no longer displays locked, maximum accuracy immediately after reacquiring satellites.
  1. Fix IP command buffer and non-response issue.
  2. Fix IP address display to use periods (.) instead of colons (:).
  3. Fix IR serial command. Was timing out.
  1. Add Option 34/35 support.
  2. Add "IP" serial command to return Option 34/35 IP addresses.
  3. Add display of Option 34/35 MAC addresses
  4. Add bit to indicate if unit has ever been locked to GPS.
  5. Update NTP status screens.
  1. Option-28 "PS" command doesn't return correct value. (Reference BZ637)
  2. Broadcasting from main and optional serial port problem at 19200 baud. (Reference BZ641)
  1. Update serial "RD" output to be consistent with 1092/3. (BZ 489)
  2. Fix Option 28 XI configuration command. (BZ 490)
  3. Will randomly acquire time when powered up with no antenna. (BZ 558)
  4. Leap second pending always 0 for Motorola 8-channel receiver. (BZ 632 and 558)
  5. NMEA GLL Broadcast needs more detail. (BZ 633)
  1. Fix power-up set defaults: Incorrectly had to wait until "SETUP" key released.
  2. Complete "Position Hold ID" (user or survey position flag)
  3. Block user from changing user position or position hold setting while survey active.
  4. Add 3D mode qualification for routine that calculates the survey position.

Downloadable Firmware (NTP/PTP Firmware)

The zip file contains all files and PDF instructions necessary to update the Network Time Protocol (NTP) / Precision Time Protocol (PTP) firmware. Reminder: Unzip the downloaded file to access the PDF instructions and individual update files.

VersionRev LevelVersion Notes

Updates are not security related.

Released 01Nov2017

1. Enhancement to allow an additional port in the future. Version tab does not change. Support > Update Log

Support  > Version
Core: 2.4
Auth01: 2.2
TPS UI Content: 2.2
Startup App: 1.3
System Monitor: 1.5
CLOI: 1.11

Support > Update Log should have the following entry:

sparky-01.07       Compiled Wed Oct 25 06:52:40 PDT 2017

Reminder: Unzip the downloaded file to access the PDF instructions and individual apf update files.


Updates are not security related.

Released 23May2017

1. Updates CLOI to 1.11. The new CLOI reduces the load on the option board CPU which allows it to serve more PTP clients.

Support  > Version
Core: 2.4
Auth01: 2.2
TPS UI Content: 2.2
Startup App: 1.3
System Monitor: 1.5
CLOI: 1.11

Reminder: Unzip the downloaded file to access the PDF instructions and individual apf update files.


Updates are not security related.

Released: 11Jan2017

1. Updates sys_monitor-01.05. The new sys_monitor corrects a bug in the frequency tuning algorithm that results in high system time offsets on some units. Whether or not a system is susceptible to this bug depends on the initial frequency of the on-board oscillator prior to tuning. It is likely that a system showing low offset now will continue to work. However, to be safe, the update is recommended.

Support  > Version
Core: 2.4
Auth01: 2.2
TPS UI Content: 2.2
Startup App: 1.3
System Monitor: 1.5
CLOI: 1.10

Reminder: Unzip the downloaded file to access the PDF instructions and individual apf update files.



Released: 17Aug2016

  1. Update NTP to latest release (4.2.8p8) to protect against a known vulnerability.
  2. Modified the NTP server configuration to allow correct responses to queries at a rate higher than once every 4 seconds.
  3. Fixed a bug that prevents the proper network filter configuration for vlan interfaces resulting in vlans not functioning.
  4. Fixed a bug preventing getting the OS version from the serial port
  5. Improved robustness of the update process.

EPROM Update (Power System Time, Frequency, and Phase Monitor Firmware)

VersionRev LevelVersion Notes
  1. The frequency was unstable off nominal frequency with an error proportional to frequency deviation. Fixed a conversion factor in the calculation. (BZ 692)
  1. Improved compatibility during transfer of correction values to option 28.

GPS Substation Clock Requirements
Download gps_substation_clock_requirements.pdf (25 kB) »

IRIG-B Time Code Accuracy, IED and System Design Issues
Download irig_accuracy_and_connection_requirements.pdf (31 kB) »

NERC PRC-08 Compliance Statement
Download pd0042900a_NERC_PRC-018_compliance_statement.pdf (75 kB) »

Time in the Power Industry: How and Why We Use It
Download TimeInThePowerIndustry.pdf (407 kB) »

Why GPS Clocks Are Not Free
Download why_gps_clocks_arent_free.pdf (12 kB) »

App Note 101: Distributing Timing Signals in a High-EMI Environment
Download application_note_101.pdf (90 kB) »

App Note 102: Synchronizing End-to End Relay Testing with Model 1088B
Download application_note_102.pdf (18 kB) »

App Note 103: Large Format Displays with Arbiter products
Download application_note_103.pdf (16 kB) »

COMTRADE Sample Rate Generator
Download ds_comt.pdf (27 kB) »

Continual Self Calibration with Power System Time, Frequency and Phase Monitor Option 28
Download power_system_time_freq_phase_monitor_continually_cal.pdf (12 kB) »

GPS Antenna Mounting Bracket
Download antenna_mnt_bracket_brief.pdf (462 kB) »

GPS Antenna Mounting Bracket Instructions
Download pd0024700_gps_antenna_mounting_bracket.pdf (580 kB) »

GNSS Antenna Preamplifier Installation Instructions
Download pd0025300_gnss_antenna_preamplifier.pdf (3 MB) »

IRIG Standard 200-16
Download irig-b_200-16.pdf (857 kB) »

IRIG-B Specifications
Download irig_b_spec_brief.pdf (488 kB) »

Internal Network Time Protocol (NTP) Server -DISCONTINUED-
Download ntp.pdf (22 kB) »

Internal Network Time Protocol (NTP) Server Español -DISCONTINUED-
Download ntp_option32_espanol.pdf (129 kB) »

Option 32: Internal NTP Server Setup and Operation Guidelines -DISCONTINUED-
Download ntp_option32_english.pdf (279 kB) »

Option 33: Dual Internal NTP Server Setup and Operation Guidelines -DISCONTINUED-
Download ntp_option33_english.pdf (301 kB) »

Option 34: Network Time Protocol (NTP)/Precision Time Protocol (PTP) Server Data Sheet
Download Option34_NTP_PTP.pdf (22 kB) »

Power System Time, Frequency and Phase Monitor
Download power_system_time_freq_phase_monitor.pdf (152 kB) »

Windows® Time Service Configuration
Download w32time.pdf (14 kB) »

Arbiter Time Service Installation Instructions
Download pd0041300_ArbiterTimeServiceInstall.pdf (382 kB) »

Chassis Dimensions
Download chassis.pdf (27 kB) »

Clock Option Selection Guide
Download clock_option_selection_guide.pdf (98 kB) »

Clock Selection Guide
Download clock_selection_guide.pdf (120 kB) »

Model 1084A/B/C Option List Español
Download 1084_optionlist_espanol.pdf (1 MB) »

Timing Products Options and Accessories
Download timing_and_frequency_options.pdf (36 kB) »

Model 1084A/B/C Firmware Upgrade Instructions
Download 1084_DST_ROM_instructions.pdf (646 kB) »

Option 28 Firmware Upgrade Instructions
Download Option28_DST_ROM_instructions.pdf (154 B) »

GPS Surge Protector Installation Instructions
Download pd0045800_surge_protector_installation_instructions.pdf (80 kB) »

Timing Signals, IRIG-B and Pulses
Download pd0043200_timing_signals_overview.pdf (197 kB) »

Catalogo de Productos de Sincronizacion y Frecuencia
Download catalogo_de_productos_de_sincronizacion_y_frecuencia.pdf (216 kB) »

Press Release: Leap Second Anomaly December 2016
Download PD0054900_LeapSecondPressRelease.pdf (70 kB) »

Antenna Cable Assemblies RoHS2 Declaration of Conformity
Download Antenna_Cable_Assemblies_RoHS2_DoC.pdf (286 kB) »

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