TM 1-1510-223-10
emission mode selector switch) allows the pilot to set
channels and frequencies, and serves as a clarifier
control in sideband mode. Depressing the control knob
causes the flashing cursor on the display to move to the
digit that the pilot desires to change. Each time the
control is depressed, the cursor moves forward to the
next digit. The digit at the cursor position is changed by
rotating the channel/ frequency selector knob.
(5) Emission mode selector switch. The
emission mode switch, placarded LSB, USB, AM, and
TEL (A3J) (concentric with the frequency/selector knob)
is used to select the operating mode of the HF
transceiver.
(6) Squelch control. A knob placarded SQ
(outer concentric with the off/volume control knob)
provides a variable squelch threshold control. This
control is used to help reduce background noise when a
signal is not being received
(7) On, off, volume control. A knob placarded
OFF, VOL (inner concentric with the squelch knob) is
used to turn the transceiver on and off, and adjust
volume. Clockwise rotation from the detent applies
power to the 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 pro-
grams 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 l) of
the frequency are displayed on the bottom of
the display.
4.
Frequency/channel selector switch - Turn
knob until desired number has been selected
The 0 in channel display will become blank
5.
Continue moving cursor and changing digits
until desired frequency appears in display.
6.
Frequency/channel selector switch - Stow
cursor by depressing repeatedly until no digit
is left flashing.
NOTE
Keying the microphone momentarily will also
stow the cursor.
7.
Antenna coupler - Tune by keying radio
momentarily. During antenna coupler tuning
process, IX on display will flash and frequency
numbers will be blank
8.
When TX annunciator stops flashing and
frequency reappears, antenna tuning cycle is
complete and radio is ready to transmit on the
selected frequency.
NOTE
Always key the radio after selecting a new frequency to
initiate antenna tuning. Otherwise poor reception or
failure to hear a ground station which is calling you may
be experienced.
(2) Programming simplex preset channels.
1.
Emission mode selector switch - USB or
AM
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