Frequency Reference Unit - Combination M-Code & SAASM Version

The FRU is a state of the art, high-precision frequency standard capable of outputting ten isolated precision 10MHz frequency reference outputs. The FRU uses an internal GPS receiver to control a precision oscillator with accuracy up to 1 x 10-12 and excellent short term stability. The FRU meets the frequency stability requirements of MIL-STD-188-164A for SHF terminals.

A particular feature of the FRU is the ultra-high isolation (>100dB) between the 10MHz outputs, eliminating interaction between 10MHz outputs when they are loaded/unloaded. The FRU incorporates a high-sensitivity 12 channel GPS Receiver.

Dual Ethernet ports are used for both monitoring/control of the FRU using Simple Network Monitoring Protocol (SNMP) as well as providing Network Time Protocol (NTP) to clients.

A Brandywine supplied user application may also be used to provide a Graphical User Interface to the FRU. The FRU is available is a number of configurations to support specific applications.

A Mobile Application version features a special vibration isolated oscillator that provides isolation of the reference source from portable generator induced phase noise. The High Performance version uses a rubidium oscillator.

A Combination SAASM & M-Code GPS receiver is available for military applications.


Model NumberDescriptionOscillator TypePower SupplyForm FactorPower TypeOutput FormatInput Format
TRU-SAASMTime Reference Generator with SAASM GPS Input - 1U Rack MountOCXOSingle AC1UACHQ, 10MHZ, IRIG, 1PPS, NTPGPS, 1PPS, HQ
FRU-SAASMFrequency Reference Generator with SAASM GPS Input - 1U Rack MountOCXOSingle AC1UACHQ, 10MHZ, 1PPS, NTPGPS, 1PPS, HQ


  • Ultra-stable GPS Disciplined Frequency Reference
  • 10 Independent 10MHz outputs
  • 1U chassis
  • Meets MIL-STD-188-164A stability requirements
  • Frequency accuracy to 1 x 10-12
  • Dual Port NTP Server


GPS Antenna Input
Connector Type BNC
1PPS Input
Connector Type DB-15
Input Level 0-10 Vpk
Input Impedance 50 Ω
Have Quick Input
Input Level 0-5 Vpk
Input Impedance 2 kΩ
10 MHz Output
Number of Outputs 10
Output Frequency 10 MHz
Accuracy 1E-12 (24hr avg.)
Output Amplitude +13 dBm
Harmonics <40 dBc
Non-Harmonic <90 dBc
Isolation <-100dBc when adjacent channel is opened or shorted
Phase Noise See datasheet for details.
Phase perturbation <5mdeg. in 0.2sec
1PPS Output
Accuracy ±50ns
Connector Type DB-15
Output Level 0-10 Vpk
Output Impedance 50 Ω
Have Quick Output
Connector Type DB-15
Output Level 0-5 Vpk
Power 90-265 VAC
Power Consumption <15 Watts
Control and Status
Connector Type 10/100 Base T Ethernet
Number of Ethernet Ports 2
Network Protocols IPV4, IPV6-ready, SNMP v1, NTP v3
Graphical Interface BWC Application
GPS Receiver
Receiver Type GB-GRAM
Frequency L1, L2 Dual Frequency
Satellite Code C/A, P(Y)
Receiver Type Parallel 12 Channel
Position Accuracy 14m SEP
Warm Start <120 seconds with Almanac, CV loaded
Mean Time Between Failures >70,000 hours
Dimensions 1U Rack mount: 19 in. x 1.72 in. x 14 in.
Humidity 95% Non-condensing
Operating 0 to +50ºC
Storage -45 to +85ºC
Temperature Shock -20 to +70 ºC 3 ºC/min
Vibration 1.5g peak. 50-2000Hz
Shock MIL-STD-188-164A para.

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