Connection Requirements
78 X72 Desiger’s Reference and User’s Guide 097-10603-01 Rev. A – November 2004
Connection Requirements
The following connections are required for 1PPS setup:
Power
GPS antenna
1PPS from the source to the X72
No serial port communication is required for initial setup unless you want to make
changes from the factory default settings. Information on setup, operation, and
integration is provided.
This document applies to X72s manufactured after November 2003 with customer
firmware versions 5.02 or higher (see Table D-2 for applicable versions).
Background
GPS technology has made possible time and frequency synchronization world wide.
Connecting the 1PPS output from a commercial (civilian) GPS receiver to an X72
provides a cost effective system that maintains highly accurate time and frequency
even when GPS signals become unavailable, for example jamming and during
antenna maintenance.
The GPS system provides worldwide 1PPS signals with extremely good long term
stability (i.e. < 1 x E
–12
averaged over 24 hours). However, the short term stability
of this signal is often compromised by various noise sources, for example
man-made, atmospheric conditions, crosstalk, RF multi-path or inter-symbol
interference, and GPS receiver oscillator limitations.
Symmetricom has pioneered the use of rubidium oscillators in telecommunications
applications. Telecommunications applications often require long term and short
term stability beyond the range of free running quartz oscillators. For example,
cellular CDMA systems often require 1PPS signals to be synchronized within 2 µs
over very long periods of time even when GPS signals are not available. To achieve
this performance, system designers must combine the benefits of short term
stability (from a rubidium or low noise OCXO) with long term stability (from GPS,
Loran-C, Glonass, or Cesium). Symmetricom is the leader in system products with
microprocessor driven circuitry that uses the GPS 1PPS system to steer various
oscillators (Cesium, Rubidium, and Quartz). These products make it possible to
combine the short term with long term stability. Now, with X72, the solution can be
even more cost effective. When used with a GPS receiver the X72 provides
telecommunications system performance levels that rival levels obtained using
Cesium oscillators.
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