system. Further clockwise rotation increases audio
Frequency Selection. The HF system has
two methods of frequency selection: direct tuning mode
and channel mode.
Direct tuning mode. In the direct
tuning mode the desired frequency is set into the display
using the frequency/channel selector knob, and stored in
memory. Only simplex operation is allowed while
operating in the direct tuning mode.
Channel mode. When the HF
control unit is in the channel mode, channels and their
frequency/channel selector knob. Frequencies in the
channel mode are stored with channel number, emission
mode (USB or AM), and transmit and receive frequency.
operator programs the same frequency for receive and
transmit. The simplex function is used by air traffic
control, ARINC, and others.
(b) Semi-duplex. In semi-duplex
frequencies, one for transmit and one for receive. The
semi-duplex function is
HF Communications Transceiver Operation.
Emission mode selector switch - USB or
Frequency/channel selector switch Turn
knob until a flashing 0 appears in the
display. HF system is now in direct tuning
Depress repeatedly until cursor is at digit
to be changed.
The first one or two digits (MHz) of
the frequency are shown on the
upper right portion of the display,
while the last four digits (kHz) of the
bottom of the display.
Frequency/channel selector switch - Turn
knob until desired number has
Frequency/Channel Selector Knob
Emission Mode Selector Switch
On, Off, Volume Control
Figure 3-5. HF Communications Transceiver Control Unit