Antenna Couplers
The antenna couplers supply these to the transceivers:
Key interlock
Tune in progress
Received RF
RF fault
Coupler fault.
The antenna coupler opens the key interlock discrete to stop the transceiver transmit mode. The coupler sends the tune in progress discrete to request tuning power from the transceiver. The RF fault is sent to the transceiver when the coupler detects a fault external to the coupler. The coupler sends the coupler fault discrete to the transceiver when it detects an internal failure.
Received RF from the antenna is sent to the transceiver during receive mode.
The antenna couplers share one common HF antenna. During the transmit mode,
only one coupler has an electrical interface with the antenna. The on-side coupler sends the off-side coupler an inhibit discrete to prevent the off-side radio from transmitting. The couplers supply transmitted RF to theantenna.
They receive push-to-talk (PTT) from the REU to enable the the coupler tune mode.
The HF transceiver supplies these to the antenna coupler:
Transmitted RF
RF carrier during tune mode
Rechannel pulse.
Modulated RF is sent to the antenna through the antenna coupler to be ransmitted. During tune mode, a low wattage RF carrier signal is sent to the coupler to match impedance between the transceiver and the antenna. The transceiver
sends the rechannel pulse to start the coupler home sequence mode.
Hf Antenna
The HF antenna receives an RF signal from the antenna coupler and transmits the RF signal to other airplane and ground HF communication systems. The antenna also receives incoming RF signals and sends the RF signals to the antenna coupler.
External Interfaces
The HF transceiver has an interface with these components from other airplane systems:
Remote electronics unit (REU)
Selective calling (SELCAL) decoder
Flight data acquisition unit
PSEU.
The remote electronics unit sends flight crew microphone (mic) audio to the transceiver to be transmitted. It also sends a PTT to start the transceivers transmit mode. The transceiver sends side tone and received audio to the REU for the flight interphone system.
The transceiver sends received audio to the SELCAL decoder.
The SELCAL decoder isolates the SELCAL code from voice audio.
The flight data acquisition unit receives a PTT from the transceiver for key event marking.
The PSEU tells the HF transceiver whether the airplane is on the ground or in the air.
Tuning interfaces General
The HF communication system uses data buses to share tuning information between the radio communication panels (RCPs) and the communication transceivers.
Tuning Bus
Each RCP has one ARINC 429 output bus.
The RCPs send tuning data to the communication transceivers.
Any RCP can tune any transceiver.
Each RCP sends tuning data and status to the other radio communication panels. This keeps the tuning data synchronized and lets any RCP tune any transceiver.
The RCP keeps the tuning data in memory. Usually, the RCP uses the tuning data from its memory to send on the output bus.
The RCP connects the CROSSTALK 1 bus directly to the output bus. This occurs for these RCP conditions:
RCP does not have power
RCP is OFF
RCP is failed.