HF COMMUNICATION SYSTEM (for 542)

General

The high frequency (HF) communication system supplies voice communication over long distances. It gives communication between airplanes or between ground stations and airplanes.

The HF system operates in the aeronautical frequency range of

2 MHz to 29.999 MHz. The system uses the surface of the earth

and an ionized layer to cause a reflection (skip) of the

communication signal. The distance between skips changes

due to the time of day, radio frequency, and airplane altitude.

Abbreviations and Acronyms

• ACARS - aircraft communications addressing and reporting system

• ACP - audio control panel

• AM - amplitude modulated

• AME - amplitude modulation equivalent

• ARINC - Aeronautical Radio Incorporated

• BITE - built-in test equipment

• comm - communication

• EE - electronic equipment

• EEC - electronic equipment compartment

• FDR - flight data recorder

• FDRS - flight data recorder system

• freq - frequency

• HF - high frequency

• I/C - interphone communication

• LCD - liquid crystal display

• LED - light emitting diode

• LRU - line replaceable unit

• mic - microphone

• PSEU - proximity switch electronics unit

• PTT - push-to-talk

• RCP - radio communication panel

• REU - remote electronics unit --дистанционный, отдельн.

• RF - radio frequency

• R/T - receive/transmit

• SELCAL - selective calling

• sq – squelch ------- сх.бесшумной настройки

• sql - squelch

• SSB - single side band

• USB - upper side band

• VSWR - voltage standing wave ratio -----КСВ

• xmit – transmit

General

The HF communication system supplies the flight crew with long range voice communication. The HF communication system can be used to communicate between airplanes and between airplanes and ground stations.

The HF communication radio uses frequency select and control signals to transmit and receive voice communication. The HF radio modulates an RF carrier signal with voice audio from the flight interphone system. During the receive mode, the HF radio demodulates the RF carrier signal. This isolates the voice audio from the RF signal. The HF transceiver sends the audio to the flight interphone system.

System Components

ILF 401, 410, 412, 424-429, 451, 501-506, 511-517, 519, 520, 524,

536, 541, 542, 551

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. ----------- Общая или раздельная

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.