Specifications

5/9/13 888-2857-001 3-89
WARNING: Disconnect primary power prior to servicing.
Section 3 Operation
Platinum VAX-C Series
Readiness (Holdover
Readiness bar graph)
Green if the graph indicates 90% or higher, red if below 90%, and gray if
the 1 PPS reference is lost.
This indicates the lock status of the OCXO (Oven Controlled crystal (X)
Oscillator). If the graph is Green, the 10MHz OCXO PLL is locked to the
1PPS reference and is capable of holdover (free running) for 24 hours.
This means that the oscillator frequency will remain within tolerance and
allow transmitter operation for 24 hours without being synchronized to its
reference.
OCXO Holdover Readiness bargraph percentage represents the difference
between the maximum and minimum oscillator control value over a 20
minute window, and is the indication of how well disciplined the
oscillator is. If the holdover status value is above 90%, then the oscillator
is only changing +/- 0.0003 Hz, and is good enough to use. The value will
never reach 100%, but when well disciplined should be 90% or greater.
The 10MHz OCXO is divided down to a 1Hz frequency and locked, via a
phase locked loop, to a GPS 1PPS (Pulse Per Second) reference signal.
The purpose is to create a synthesized 1PPS signal which is used as a
timing signal, for example, to synchronize a single frequency network.
The 10 MHz OCXO signal is also used as a reference for the local
oscillator, which determines the RF output frequency of the exciter.
The synthesized 1PPS signal will be present even when the GPS 1PPS
reference is missing. In that case, the 10 MHz OCXO holdover oscillator
will be free running.
Time Remaining When the 1PPS reference is lost, the OCXO Holdover Readiness graph
turns gray, and the 10 MHz OCXO is free running. The Holdover Time
Remaining indication starts to count down from 24 hours. When its time
reaches zero, the transmitter will mute if it is in the SFN mode
When the reference is restored and the oscillator starts to lock, the OCXO
Holdover Readiness graph indication will start to increase. While it is
below 90%, the graph is Red. The exciter, if in the SFN mode, will be
muted. When the graph reaches 90% or higher, it will turn Green, and the
exciter, if in the SFN mode, will unmute.
Softkeys
Status Displays Status screen.
Exciter Home Displays Exciter Home screen.
Table 3-59 Xmtr Home> Exciter Home> Status >PFRU Status