HF SYSTEM -RADIO TUNING PANEL
When you select an offside radio, two offside tuning lights come on. One light is on the RTP that the flight crew uses to make the selection. The other light is on the onside RTP of the selected radio.
The HF sensitivity control sets the RF sensitivity level of the onside HF transceiver. The left RTP sets the left HF sensitivity. The right RTP sets the right HF sensitivity. The center RTP HF sensitivity control does not connect to any transceiver.
Use the AM switch to operate the selected transceiver in the amplitude modulation (AM) mode. In the AM mode, the light in the AM switch comes on. If the AM switch is not selected, the HF communication transceiver operates in the upper side band (USB) mode.
When either HF transceiver is selected, the AM mode light indicates the last commanded mode of the selected transceiver. The mode of an HF transceiver will remain unchanged until the HF transceiver is selected by any RTP and commanded to change mode.
If the same HF transceiver is selected on more than one RTP, every RTP selecting that transceiver will show the same mode.
If either the left or right RTP is switched from HF to VHF, the AM light on that RTP will show the last commanded mode of the on-side transceiver.
When the center RTP is switched to VHF, the AM mode light will be off.
After an HF transceiver is commanded to the AM mode, the AM mode light remains ON to serve as a reminder that if the HF transceiver is selected on any audio control panel, the HF transmission will still be in AM mode. Deselecting an HF transceiver at an RTP will not change the HF mode. The HF transceiver remains in the last commanded mode even when the RTP is subsequently used to tune VHF transceivers. The AM mode light also remains on because the HF AM switching function is inhibited when the RTP is selected to a VHF radio.
Push the radio tuning panel off switch to stop the operation of the RTP. When the RTP is off, the radio tuning panel off light comes on and all functions stop except these three:
*
The frequency windows continue to show any current fault
*
The RTP continues to receive 28v dc
*
The RTP continues to send BITE information to the AIMS central maintenance computer function (CMCF).
BITE
The RTP tests itself continuously. The RTP shows PANEL FAIL in the two frequency windows if the RTP has an internal failure or if there is a system failure.
The two frequency display windows show all dashes if the flight crew selects a failed radio.
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HF SYSTEM -RADIO TUNING PANEL
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HF SYSTEM -AUDIO CONTROL PANEL
General
The audio control panel (ACP) supplies transmitter selection, receiver selection and volume control for the left and right HF transceivers.
The operator transmits on only one HF system at a time. The ACP permits the operator to listen to one or both HF systems at the same time.
Control and Indications
Push an HF receiver volume control to listen to an HF receiver. Rotate the receiver volume control for volume control. The receive light above the control shows green when a receiver volume control is on. Push both HF receiver volume controls to listen to both HF radios at the same time.
Push an HF transmitter select switch to select an HF transceiver for transmission. The mic light shows green to show the selected system. Push the mic/interphone switch to connect the microphone to the transceiver and to key the transceiver.
The call light comes on when the SELCAL system detects a call for the system.
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HF SYSTEM -NORMAL TUNING
General
The HF communication system uses three radio tuning panels (RTPs). The RTPs share tuning data on crosstalk buses. This allows any RTP to tune any transceiver.
Normal Tuning
Under normal conditions, all three RTPs are on.
When the left RTP is on, it sends a grounded port select discrete to the left HF transceiver. The left transceiver uses port A as its input port when its port select discrete is a ground. Port A of the left transceiver connects to the left RTP. The left RTP supplies tuning data to the left HF transceiver.
The interface between the right HF transceiver and the right RTP is the same as the left.
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