4-42
888-2586-001
9/15/06
WARNING: Disconnect primary power prior to servicing.
Platinum Z16HD+
Section 4 Overall System Theory
•
Forward Factor - 0.015393
•
Reflect Factor - 0.000613
•
Cal Frequency - 98MHz
•
Operating Frequency - 98MHz
•
Cal APC Factor - 15.15
•
TPO 100% - 07.00kW
•
Max High - 07.30kW
•
Max Low - User Settable
•
UPS Setting - User Settable
•
Low Power Alarm - User Settable
•
VSWR Foldback - 1.3:1
•
VSWR Fault - 1.7:1
4.8.1.2
APC, Automatic Power Control
One important function of the Master Controller is transmitter power control, which is
accomplished via the APC Loop. In addition to transmitter power level control, the
APC Loop also adjusts for slight power deviations by varying the control voltage to the
RF source, via the Life Support board, indirectly proportionate with the forward power.
In other words, if the forward power output goes up slightly, the RF source output will
be reduced, which will in turn reduce the PA RF output. If the forward power output
goes down, the RF Source output will be increased, which will increase the PA RF
output to compensate for power fluctuations.
The APC loop starts at the forward power directional coupler. The forward sample is
connected to the Life Support Board where it is calibrated with R127 for about 8.9V@
100% TPO at TP9. This voltage sample is then sent to the Master Controller (schematic
sheet 7) where it is squared by multiplier chip U1 (to make the voltage from the coupler
proportional to power) and divided by 10. This is then sent to U5-6 where it is
compared to APC_REF voltage (APC Reference).
APC_REF is the DC output of a D/A Converter or DAC whose input is called
DAC_APC_REF and is controlled by the RAISE and LOWER buttons on the front of
the controller (or by the remote control inputs) or can be varied automatically by the
Master Controller’s foldback routines. Pressing RAISE increases the APC_REF voltage
and pressing LOWER decreases it. The DAC_APC_REF is responsible for all
transmitter power control functions including power level, foldbacks and mute. This
makes it a very important number to know and understand for troubleshooting.
Содержание Platinum Z16HD+
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