Symmetricom 5401 User Manual

PN 8500-0150, Rev. A, May 2005

1

Operating Manual

Introduction

The purpose of the Symmetricom 5401 Airborne Disciplined Rubidium and 5402 Disciplined 
Rubidium Oscillator (DRO) is to provide a precise time and frequency reference for other 
equipment. The DRO will base this reference on a precise 1 PPS input, typically from a GPS 
Receiver. At the 1 PPS time signal input rollover, the DRO will measure the time difference 
between it and the internal Rubidium oscillator. It will continuously correct the oscillator error, 
smooth the GPS Receiver noise due to ephemeris and time switching errors, and provide 
smoothed, coherent 1 PPS time reference and a 10 MHz frequency reference signal outputs. 

The DRO contains a Low Profile Rubidium Oscillator (LPRO) that is controlled by a High 
Resolution Disciplining assembly along with the necessary Power Supply, Buffers and 
Distribution Amplifiers. 

The High Resolution Disciplining assembly contains the logic to discipline the Rubidium 
oscillator to an external 1 PPS input. This assembly also contains a 10 MHz oven oscillator 
that is phase locked to the Rubidium. This provides a source for low noise 10 MHz sine wave 
outputs. 

Two 3 Channel Distribution Amplifiers are provided to output six (6) 10 MHz sine wave 
outputs. A 1 PPS Buffer generates six (6) 1 PPS outputs. 

The DRO also has an RS232 I/O port that is used for setup, control, and to output the unit's 
status. 

Except for the power supplies, the 5401 and 5402 are electrically identical. The power and 
serial RS-232 connectors are different as are the signal input and output connectors. Refer to 

 and 

 for illustrations of the two configurations of the DRO. Details are given 

in 

In this Operating Manual, the term "DRO" is used when the information applies equally to 
both the Symmetricom 5401 and the Symmetricom 5402.