Specifications

4-10 888-2857-004 5/9/13
WARNING: Disconnect primary power prior to servicing.
Section 4 Theory of Operation
Platinum VAX-C Series
the +24V, +12V, +12Vosc, +5V, and -12V power supply interface board dc
outputs energized for one minute following a power failure. During this time
the PA assembly is not powered.
• It keeps the oscillator circuits and the internal GPS receiver operating for an
additional fifteen minutes following the one minute modulator controller
backup operation. It accomplishes this by de-energizing all but the +12Vosc
power supply outputs.
• During the last fifteen minutes of battery backup operation, the battery
backup maintains power to the 10MHz and 1PPS Input circuitry on the
Signal Processing board and the FPGA, OCXO and GPS circuitry on the
PFRU. By powering these circuits the modulator can maintain the 10MHz
OCXO discipline loop when the transmitter loses power. The OCXO can take
three minutes to stabilize from a cold start and the discipline loop itself can
take an hour to reach the maximum precision; having the discipline loop
active during a power outage enables the VAX-C transmitter to return to air
faster with greater frequency accuracy.
Figure 4-4 Battery Backup Block Diagram