The hf antenna coupler matches the antenna impedance to the transceiver output over the hf frequency range. During the transmit mode, the antenna coupler receives modulated rf

from the transceiver and sends it to the antenna. During the receive mode, the antenna coupler receives modulated RF from the antenna and sends it to the transceiver.

The HF antenna transmits and receives audio modulated RF signals.

External Interface

The HF communication system connects with these

components/systems:

• Remote electronics unit (REU)

• SELCAL decoder unit

• Air/ground relay

• Flight data acquisition unit (FDAU). -------приобретение

System Operation

The control panel sends selected frequency information and control signals to the transceiver. The audio control panel sends these signals to the REU:

• HF radio select signal

• Receive volume control

• Push-to-talk (PTT).

During transmit, microphone audio and PTT signals go to the

HF transceiver through the REU. The transceiver uses the

microphone audio to modulate an RF carrier signal generated

in the transceiver. The transceiver sends the modulated RF

signal through the antenna coupler to the antenna for

transmission to other airplanes and ground stations.

Also during transmit, the flight data acquisition unit receives a

PTT signal from the transceiver. The flight data acquisition unit

uses the PTT for key event marking to record the transmit event.

During receive, the antenna receives a modulated RF signal

and sends it through the antenna coupler to the transceiver. The

transceiver demodulates or isolates the audio from the RF

carrier. The received audio goes from the HF transceiver to the

flight interphone speakers and headsets through the REU.

The SELCAL decoder unit receives audio from the HF transceiver. The SELCAL decoder unit monitors the audio for SELCAL calls that come from the ground station.

The HF transceiver receives an air/ground discrete. The HF

transceiver uses the discrete to calculate flight legs for internal fault memory.

Flight Compartment

The radio communication panels are on the P8 aft electronics panel.

The audio control panels (ACPs) are part of the flight interphone

system. The ACPs have an interface with the HF communication

system through the REU. The captain and first officer ACPs are

on the P8 aft electronics panel. The first observer ACP is on the

P5 aft overhead panel.

The HF transceivers are on the E6-2 shelf.

ANTENNA COMPONENT LOCATIONS

General

The antenna couplers are inside the vertical stabilizer.

WARNING: MAKE SURE PERSONNEL STAY A MINIMUM OF SIX FEET (TWO METERS) AWAY FROM THE VERTICAL STABILIZER WHEN THE HF SYSTEM TRANSMITS.

RF ENERGY FROM THE HF COMMUNICATION ANTENNA CAN CAUSE INJURIES TO PERSONNEL.

HF COMMUNICATION SYSTEM – INTERFACES

Power

The 115v ac transfer (XFR) bus supplies three-phase power to the HF transceiver.

The transceiver supplies 115v ac and 28v dc power to the HF

antenna coupler.

HF Transceiver

The HF transceiver has an interface with these components:

• RCP 1, 2, and 3

• Selective calling (SELCAL) decoder

• Remote electronics unit (REU)

• HF antenna coupler

• Flight data acquisition unit ------------------------приобретение

• Proximity switch electronics unit (PSEU). –---выключатель сближения с землей

Radio Communication Panel

RCP 1 supplies frequency information to the HF 1 transceiver on an ARINC 429 bus to port A and to the HF 2 transceiver on port B. RCP 2 supplies frequency information to the HF 1 transceiver on an ARINC 429 bus to port B and to the HF 2 transceiver on port A. For more information about tuning interfaces, see HF Communication System - Tuning Interfaces.

The HF transceiver supplies the condition of the transceiver to the radio communication panels. The condition of the transceiver is one of the two: OK or FAILED.

The radio communication panel supplies these to the HF transceiver:

• Amplitude modulated or single side-band control

• Tuning data

• Port select discrete.

RADIO COMMUNICATION PANEL