panel to the left of the tuning knobs is used to store in
memory the displayed data when programming preset
(8) OFF / VOLUME Control. A knob,
placarded OFF / VOLUME, located on the HF control
panel turns the system off and on and controls volume.
Clockwise rotation from the detent applies power to
the system. Further clockwise rotation increases
audio output level.
(9) SQUELCH Control. A knob placarded
SQUELCH on the HF control unit provides a variable
squelch threshold control.
(10) CLARIFIER Control. A knob placarded
CLARIFIER PULL ON located on the lower left corner
of the HF control unit is used to eliminate unnatural
audio quality when operating in the Single Sideband
(SSB) mode by slightly shifting the receiver generated
frequency to match the frequency of the signal being
received. To operate the clarifier, the knob is pulled
out and rotated in either direction from the index mark
(which is located directly above the clarifier knob) until
the audio quality is optimized. When the voice quality
is natural the clarifier knob should be pushed in.
Turning the clarifier knob has no effect when it is
c. Frequency Selection. The HF system has
two methods of frequency selection, frequency mode
and channel mode. In the frequency mode,
frequencies are tuned directly on the display using the
tuning knobs. In the channel mode, preset channels
are programmed with an assigned channel number (1
through 99) and stored in memory.
(1) Frequency Mode. In the frequency
mode, the desired frequency is set into the display
using the tuning knobs. Only simplex operation is
allowed while operating in the frequency mode.
(2) Channel Mode. When the HF control unit
is in the channel mode, channels and their respective
frequencies are changed using the tuning knobs. To
place the unit into the channel mode, press the
FREQ/CHAN switch. This allows access to existing
programmed channels. Frequencies in the channel
mode are stored with channel number, emission mode
(USB, LSB, or AM), and transmit and receive
(3) Program Mode. When the HF control unit
is in the program mode, channel numbers, emission
mode (USB, LSB, or AM), and transmit and receive
frequency are set up and stored in memory. The
program mode is entered from the channel mode by
pressing the PGM switch with a pencil or other pointed
object. When in the program mode, channel number,
emission mode, and transmit frequency are all
displayed. Transmitter operation is inhibited. The
transmit frequency may be examined by keying the
microphone. Channels may be programmed for the
following types of operation.
programs a frequency in the receive portion of transmit
frequency. The transmitter is locked out when a
channel has been programmed for receive only
operation. The receive-only function is used for
listening to weather, time, omega status, frequency
standard, and geophysical alert broadcasts.
(b) Simplex Operation. The operator
programs the same frequency in receive and transmit,
and assigns an operating mode (USB, LSB, or AM).
The simplex function is used by air traffic control,
ARINC, and others.
frequencies, one for transmit and one for receive.
The semi-duplex function is used by maritime
(a) Frequency/Channel Switch FREQ
emission mode (USB, LSB, or AM).
frequency, then stow cursor.
(d) Antenna Coupler Tune, press
(2) Programming Preset Channels.
(a) Receive Only.
1. Cursor Stow if a frequency digit
2. Tuning Knobs Select channel to
be preset and desired frequency.