777 AMM 飞机维护手册 通讯 Communications 1(24)

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RF Assembly
The RF assembly receives RF signals from the radio frequency unit (RFU) and increases the signal level. The RF assembly sends the output to the HPR or to the top LNA/DIP.
The RF assembly also monitors the reflected power level, forward power level, and RF input power level. It sends this data to the I/O processor. The levels of these signals tell the I/O processor how to adjust the gain of the amplifier.
Input/Output Processor
The I/O processor controls all the functions of the HPA. It receives commands from the satellite data unit (SDU) on an ARINC 429 data bus. In the class A amplifier, the I/O processor also receives a mute signal from each beam steering unit (BSU). The HPA uses the mute signal to turn off its output when the SATCOM system switches from one high gain antenna to the other.
The processor monitors:
*
Reflected power

*
Forward power

*
RF power input

*
Amplifier temperature

*
Power supply operations.

The attenuator control adjusts the RF signal strength to the RF assembly. In the class A amplifier, the processor sends a mute signal to the RF assembly to shut down the RF transmit section.
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SATCOM SYSTEM -HIGH POWER AMPLIFIER FUNCTIONAL DESCRIPTION

In an over-temperature condition, the I/O processor sends output power control signals to the RF assembly. This decreases the output power and gives the amplifier circuits time to cool.
The processor sends HPA status to the SDU on an ARINC 429 data bus.
Thermal Monitor
The thermal monitor tells the I/O processor of high temperature conditions in the HPA.
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SATCOM SYSTEM -HIGH POWER AMPLIFIER FUNCTIONAL DESCRIPTION

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SATCOM SYSTEM -RADIO FREQUENCY COMBINER FUNCTIONAL DESCRIPTION
General
The radio frequency combiner (RFC) permits SATCOM to operate more than one antenna. The RFC gets the RF signal from the active low noise amplifier/diplexer and sends it to the RFU.
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SATCOM SYSTEM -RADIO FREQUENCY COMBINER FUNCTIONAL DESCRIPTION

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SATCOM SYSTEM -RADIO FREQUENCY SPLITTER FUNCTIONAL DESCRIPTION
General
The radio frequency splitter (RFS) permits SATCOM to send RF signals to more than one high power amplifier. The RFS divides the RF signal from the RFU and sends it to both high power amplifiers.
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SATCOM SYSTEM -RADIO FREQUENCY SPLITTER FUNCTIONAL DESCRIPTION

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SATCOM SYSTEM -CONTROL AND STATUS PAGES

General
The control display unit (CDU) has SATCOM pages that give control and status of the SATCOM system.
Satcom Main Menu
The SATCOM main menu shows:
*
The name selected for call on channel 1 or 2.

*
Call controls

*
SATCOM directory access

*
Access to SATCOM submenus.

For each channel, SATCOM shows these items:
*
Channel status

*
Call connection commands

*
Call disconnect commands

*
The call destination name chosen from the directory.

SATCOM Submenu
The submenu shows the current log-on status of SATCOM. It also has selections to let you control the log-on and log-off. Other selections let you see the status of each channel and check the configuration of LRUs.
SATCOM Directory
The SATCOM directory pages show the labels for each phone number in the directory.
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777 AIRCRAFT MAINTENANCE MANUAL

SATCOM SYSTEM -CONTROL AND STATUS PAGES

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SATCOM SYSTEM -LOG ON

General
To use the SATCOM system, the airplane must log-on to a communication service company.
Automatic Log-On
An automatic log-on occurs when the system powers up. The SATCOM system uses satellite frequencies in memory to find a satellite transmit signal. When the SATCOM system finds an active frequency from the satellite, it locks on to it. The system then uses the satellite as a relay to log-on to a ground station.
　
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