(3) Tuning Knobs. Two concentric tuning
knobs, located on the right side of the NAV receiver
control panel, are used to set the frequency or channel
shown on the digital display, depending upon the
mode of operation being used.
(a) Frequency Standby Entry Mode.
When the unit is in the frequency standby entry mode,
the larger concentric knob is used to increase or
decrease the first two digits to the left of the decimal
point (08 to 17), of the standby digital display. When
the larger concentric knob is turned to increase the
digits above 17, the display will start over at 08.
Conversely, when the knob is turned to decrease the
digits below 08, the display will start over at 17. The
smaller concentric knob is used to set frequencies with
50 kHz spacing (i.e., .75, .80, .85, .90, etc.).
When in the active entry mode, the tuning knobs
operate the same as they do in the standby entry
mode, but will change the active digital display
frequency, rather than the standby frequency.
(c) Channel Mode. When the unit is in
the channel mode, turning either tuning knob will
change the channel number in the upper display and
the corresponding frequency in the lower display.
(d) Program Mode. When the unit is in
the program mode, the tuning knobs are used to select
the channel number in the upper display (when
flashing) or the channel frequency in the lower display
(4) CHAN Switch. A momentary push-button
switch, placarded CHAN, located on the lower portion
of the NAV control unit, is used to put the unit into the
channel and program modes. Momentarily pressing
the channel switch while in a frequency mode puts the
unit into the channel mode. Holding the channel
switch for longer than 2 seconds puts the unit into the
(5) OFF / VOL Control. A control knob on
the front of the VHF control unit, placarded OFF / VOL,
controls the operation of the unit. Turning the knob in
the clockwise direction from the OFF position (detent)
applies power to the unit, and audio volume output is
increased as the knob is turned further to the right.
f. Modes of Operation. The NAV receiver
control unit may be operated in the frequency mode
(either standby entry or active entry), channel mode, or
(1) Frequency Modes. The NAV receiver
control unit may be operated in standby entry and
(a) Standby Entry. When the unit is
operated in the standby entry frequency mode, a new
frequency is set on the standby digital display using
the tuning knobs. When the operator is ready, the
frequency is then transferred to the active display by
pressing the frequency transfer switch.
(b) Active Entry. When the unit is
operated in the active entry frequency mode, a new
frequency is set on the active digital display using the
tuning knobs. The active entry mode is entered from
the standby entry mode by pressing the transfer switch
for longer than 2 seconds. The standby digital display
will be blank while the unit is in the active mode.
(2) Channel Mode. When the NAV receiver
control unit is in the channel mode, the upper digital
display will show a channel number (1 through 9) and
the lower digital display will show the frequency
assigned to the channel number in the upper digital
display. The tuning knobs will change the channel
number and corresponding frequency shown on the
displays. The channel mode is entered by
momentarily pressing the CHAN button located on the
VHF transceiver control unit. If there are no valid
frequencies programmed, the unit will display a CH 1
in the upper display and dashes in the lower display.
The unit can be changed from the channel mode to the
frequency mode in three ways.
(a) Momentarily pressing the transfer
switch will return the unit to the frequency mode,
placing the channel frequency in the active display and
the previous active frequency in the standby display.
(b) Momentarily pressing the
switch will return the unit to the frequency mode, and
will return the active and standby displays to what they
displayed prior to entering the channel mode.
(c) The unit will return to the frequency
mode if no knob activity takes place for 5 seconds
after the unit was put into channel mode. When
returned in this manner, the channel frequency will be
put into the standby display with the active frequency
remaining as it was before entering channel mode. If
no frequencies were programmed, the frequencies will
remain the same as they were before entering channel
(3) Program Mode. The preset channels and
frequencies are set using the program mode.
Pressing and holding the CHAN switch for 2 seconds
will place the unit into the program mode. A P and a