TM 1-1510-224-10
system. Further clockwise rotation increases audio
output level.
c.
Frequency Selection. The HF system has
two methods of frequency selection: direct tuning mode
and channel mode.
(1)
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.
(2)
Channel mode. When the HF
control unit is in the channel mode, channels and their
respective
frequencies
are
changed
using
the
frequency/channel selector knob. Frequencies in the
channel mode are stored with channel number, emission
mode (USB or AM), and transmit and receive frequency.
(a)
Simplex
operation.
The
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
operation
the
operator
programs
two
different
frequencies, one for transmit and one for receive. The
semi-duplex function is
used
by
maritime
radiotelephone
network
(public
correspondence) stations.
d.
HF Communications Transceiver Operation.
(1)
Direct
frequency
tuning
operation
(simplex only).
1.
Emission mode selector switch - USB or
AM.
2.
Frequency/channel selector switch Turn
knob until a flashing 0 appears in the
display. HF system is now in direct tuning
mode.
3.
Frequency/channel
selector
switch
Depress repeatedly until cursor is at digit
to be changed.
NOTE
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
frequency
are
displayed
on
the
bottom of the display.
4.
Frequency/channel selector switch - Turn
knob until desired number has
1.
Digital Display
2.
Light Sensor
3.
Store Switch
4.
Frequency/Channel Selector Knob
5.
Emission Mode Selector Switch
6.
Squelch Control
7.
On, Off, Volume Control
A93FE0D0099 C
Figure 3-5. HF Communications Transceiver Control Unit
3-12
