757
MAINTENANCE MANUAL
CAPTAIN'S CAPTAIN'SFIRST OFFICER'S COCKPIT FIRST OFFICER'S COCKPIT
ATTENDANT SPEAKERS
(VIDEO) 23-32-00
Communication System Block Diagram Figure 1
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MAINTENANCE MANUAL
L. The voice recorder system (23-71) records flight compartment communications and conversations. The latest 30 or 120 minutes of recorded conversation is available on tape or from solid state memory. Erasing is accomplished only when the airplane is on the ground with the parking brake set.
3. Antenna Locations (Fig. 2)
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A. The VHF communication antennas are located on the upper and lower centerline of the fuselage at the following locations:
(1)
The left VHF Communication antenna is installed on the top forward centerline of the fuselage.
(2)
The right VHF Communication antenna is installed on the lower forward centerline of the fuselage.
B. The HF communications antenna is located in the leading edge of the vertical stabilizer.
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MAINTENANCE MANUAL
Figure 2
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757 MAINTENANCE MANUAL
HF COMMUNICATION SYSTEM - DESCRIPTION AND OPERATION
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1. General_______
A. Two HF (high frequency) communication systems (referred to as the HF systems) provide long-range air-to-ground or air-to-air communications.
B. The HF system consists of an HF communication transceiver, an HF communication control panel, an HF communication antenna coupler, and a HF communication antenna. The HF communication antenna is a slot-type, shunt-fed antenna. If two HF systems are installed, the HF systems share the single HF communication antenna.
C. The HF systems operate in the 2.800 to 23.999 megahertz (MHz) frequency range on 21,200 channels or in the 2.000 to 29.999 MHz frequency range on 28,000 channels in either amplitude modulated (AM) or upper side band (USB) modes.
D. The audio, microphone and PTT functions of the HF system are interfaced with the audio selector panels (ASP's) of the flight interphone system (AMM 23-51-00/001).
E. The left HF system utilizes 115v ac 400 Hz 3-phase power from the left bus. The right HF system (if installed) utilizes 115v ac 400 Hz 3-phase power from the right bus. The HF COMM LEFT and HF COMM RIGHT circuit breakers located on the overhead panel P11 control power to the HF systems.
2. Component Details (Fig. 1)_________________
A. HF Communication Control Panel
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