351804-1 Rev. 100
COM5000-8 TECHNICAL MANUAL
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4.4
COMBINER MODULE
The Combiner module receives signals from the four 1.25kW PA modules and combines the signals,
in-phase, to yield the 5kW output signal. The output signal is routed through a VSWR Detector (located
inside the combiner module) to provide forward and reflected power information for the System Controller.
4.5
SYSTEM CONTROLLER MODULE
A block diagram of the System Controller module is shown in figure 4.5.
The System Controller contains a Linear Power Supply, the Splitter/ALC PCB Assembly and the System
Controller PCB Assembly. Together they control and protect the various modules comprising the
Transmitter system.
The Splitter/ALC PCB circuitry comprises a 4-way, in-phase, splitter that divides the RF input signal from the
Exciter into four signals that each drives a PA module. The RF input signal is rectified to provide a DC
voltage to the Input Drive monitoring circuitry. The detected input drive level is read by the microprocessor
and provides information to prevent input overdrive.
The System Controller PCB contains the following functional groups:
A) Combiner Control and monitoring circuitry provides ON/OFF switching of the Combiner FAN and
receives information on the Combiner heatsink temperature.
Voltages proportional to the forward (VF) and reflected (VR) power are routed to the Fault Sensing
circuitry and to the Meter Drivers. VF and VR are also applied to the automatic level control (ALC)
circuitry to maintain constant output power as well as protection against excessive antenna VSWR.
With an antenna VSWR of 2:1, output power is reduced to approximately 2500-3500 watts. With a 3:1
antenna VSWR, output power is reduced to approximately 1500-2000 watts. These are typical values
only and are not guaranteed under all possible antenna impedances.
VF and VR voltages are read by the microprocessor and used in calculation of system gain and VSWR.
B) PA module control and monitoring circuitry communicates with the PA Controller inside each PA
module. Filter select information is transmitted to and status information is received from the PA
modules.
The PTT (Key) output from the microprocessor is hard-wired to the PA modules.
C) The Power Supply control and monitoring circuitry turns the Power Supply ON and OFF and monitors
the supply voltage.
D) Cabinet Interlock information is processed by the microprocessor.
