777 AIRCRAFT MAINTENANCE MANUAL
HF SYSTEM -E6 RACK COMPONENT LOCATIONS
HF System Component Locations
The HF communication transceivers are in the E6 rack.
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777 AIRCRAFT MAINTENANCE MANUAL
HF SYSTEM -E6 RACK COMPONENT LOCATIONS
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HF SYSTEM -VERTICAL STABILIZER COMPONENT LOCATION
HF System Component Locations
These are the three HF system components in the vertical stabilizer:
*
HF communication antenna
*
Two HF antenna couplers.
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HF SYSTEM -VERTICAL STABILIZER COMPONENT LOCATION
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HF SYSTEM -POWER INTERFACE
General
The left transfer bus sends 115v ac three-phase power to the left HF communication transceiver.
The left HF communication transceiver supplies 115v ac single phase to the left HF antenna coupler for operational power. It also supplies 28v dc for the key interlock function.
The right HF communication system is the same as the left, except that it uses power from the right ac sec 2 bus.
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777 AIRCRAFT MAINTENANCE MANUAL
HF SYSTEM -POWER INTERFACE
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HF SYSTEM -TUNING INTERFACE
General
The HF communication system uses data buses to share tuning information between these:
*
Radio tuning panels (RTPs)
*
HF communication transceivers
*
Airplane information management system (AIMS) cabinets.
Tuning Buses
The RTPs send tuning data to the HF communication transceivers. Any RTP can tune any transceiver.
Each RTP has these two ARINC 429 output buses:
*
Tuning bus
*
Crosstalk bus.
Both the left and right RTPs send tuning data to both HF communication transceivers and to the left and right AIMS cabinets.
The center RTP sends its tuning bus output to the left and right RTPs in case of failure.
Port Select Discrete
Each HF communication transceiver has two tuning data input ports, port A and port B. The transceiver uses the port select discrete to select its input port. A grounded port select discrete causes the transceiver to use port A. An open port select discrete causes the transceiver to use port B.
The port select discrete for the left HF communication transceiver comes from the left RTP. The port select discrete for the right HF transceiver comes from the right RTP.
Crosstalk Buses
Each RTP sends tuning data to the other RTPs on crosstalk buses. Synchronized tuning data allows any RTP to tune any transceiver.
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777 AIRCRAFT MAINTENANCE MANUAL
HF SYSTEM -TUNING INTERFACE
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HF SYSTEM -RECEIVE/TRANSMIT INTERFACES
General
You use an audio control panel (ACP) to select an HF communication transceiver for voice communication. You use a radio tuning panel (RTP) to select a frequency or adjust HF sensitivity of the transceiver. A push-to-talk (PTT) signal from any mic switch activates the selected transceiver.
Signal Flow -Transmit
You select a transmit switch on any ACP and push a mic switch to transmit. The audio management unit (AMU) sends the mic audio and the PTT signal to the selected HF transceiver. The PTT also goes to the applicable antenna coupler. When the transceiver gets a key interlock from the antenna coupler, it changes the mic audio to an RF signal. The transceiver sends the RF signal to the antenna coupler. Only one antenna coupler can transmit at a time. The antenna coupler sends the RF signal to the HF antenna. The HF antenna transmits the signal.
WARNING: DO NOT TRANSMIT WITH THE HF COMMUNICATION SYSTEM WHILE THE AIRPLANE IS REFUELED OR DEFUELED. AN EXPLOSION CAN CAUSE INJURIES TO PERSONNEL AND DAMAGE TO THE AIRPLANE.
WARNING: MAKE SURE PERSONNEL STAY A MINIMUM OF 6 FEET AWAY FROM THE VERTICAL STABILIZER WHEN THE HF SYSTEM TRANSMITS. RF ENERGY FROM THE HF COMMUNICATION ANTENNA CAN CAUSE INJURIES TO PERSONNEL.
The antenna coupler tunes itself to match the output impedance
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