System Components

The HF communication system has two HF radios. These are

the components:

· Radio communication panel

· HF transceiver

· HF antenna coupler

· Common or shared HF antenna.

The radio communication panel (RCP) supplies selected frequency information and control signals to tune the HF transceivers and make radio selections. You can use the RCP to select amplitude modulated (AM) or upper side-band (USB) operation. Use the RF sensitivity control to improve HF reception. The RCPs can select and control the frequency of any HF communication radio. The HF transceiver transmits and receives information. The transceiver transmit circuits use flight interphone audio to modulate an RF carrier signal. This voice information goes to other airplanes and ground stations.

The receive circuits demodulate the received RF carrier signal to isolate the audio. The received audio is used by the flight crew or other airplane systems.

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).

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.

Дата добавления: 2015-10-23