6. Maintenance
6.1. Overview
The ptf 3203A GlobalTyme GPS receiver uses state-of-the art solid state
and semi-conductor components together with some specialty
components such as the internal OCXO (or Rubidium) oscillator, the
vacuum fluorescent display, and the membrane keypad (if fitted).
All of the components are selected for their inherent high reliability, and
as advanced techniques with highly sophisticated equipment, are used for
assembly and test of the unit.
Due to the above, very little periodic maintenance of the unit is required
and the units can be expected to deliver many years of trouble free
operation. The sections below describe the few items that may require
periodic maintenance.
Any maintenance or service of the unit should be performed at a Precise
Time and Frequency, Inc. authorized facility, to insure the appropriate
equipment and expertise is available.
6.2. Local Oscillator
Two fundamental technologies are available as the local oscillator within
the unit, namely a Crystal Oscillator (TCXO or OCXO) or a rubidium
atomic oscillator (Rb). Depending upon the requirement of the application,
either may be fitted upon request.
In normal operation, the ptf 3203A “disciplines” (phase locks) the local
oscillator to the received GPS one pulse per second signal, to maintain
the unit’s frequency to the exact frequency generated by the atomic clock
ensemble of the GPS system.
Due to aging characteristics of the local oscillator, over a period of time
the control voltage used for disciplining moves in one direction, and after
a very long period (>10 years) may reach the limit of it’s control voltage.
If this occurs, the unit will display a “Control Limit Reached” error
message and the unit should be returned for mechanical adjustment to
“center” the control voltage.
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