channel number will be shown in the active display
and a frequency or dashes will be shown in the
standby display. Immediately after entering the
program mode, the channel number will begin to flash,
indicating that rotating the tuning knobs will change the
channel number. Momentarily pressing the transfer
switch will cause the channel number to stop flashing
and cause the frequency to begin flashing, indicating
that rotating the tuning knobs will change the
frequency. Momentarily pressing the CHAN switch will
return the unit to the frequency mode. The standby
frequency will return to what it was prior to entering the
program mode. The unit will automatically return to
the frequency mode if no front panel activity takes
place for 20 seconds.
(1) Turn On Procedure.
1. Avionics Master Switch (overhead
control panel, Figure 2-15) ON.
2. OFF/VOL Knob Turn clockwise out
of detent, then press to turn off
automatic squelch circuit. Continue
headphones or speaker, assuring that
receiver is operating, then set audio
volume to desired level. Press knob
again to return unit to automatic
(2) Receiver Operating Procedure.
1. MODE Push-Button Switch As
2. Tuning Knobs Set desired frequency
3. NAV 1 Receiver Audio Switch (audio
control panel, Figure 3C-1) ON.
4. VOL Control Adjust as required.
(3) Shutdown Procedure.
counterclockwise to OFF position.
3C-22. TACAN/DME (KTU-709).
a. Description. The TACAN system is a polar
coordinate UHF navigation system that provides
relative bearing and slant range distance information
with respect to a selected TACAN or VORTAC ground
station. The effective range of the TACAN is limited to
the line-of-sight. Actual operating range depends on
the altitude of the aircraft, weather, type of terrain,
location and altitude of the ground transmitter, and
TACAN audio is applied to the audio control
panel. The TACAN system also has a self-test mode
for both bearing and distance functions. The
NAV/TAC control unit, Figure 3C-17, tunes the KTU-
709 to all 252 TACAN channels and all DME channels.
TACAN course deviation information may be displayed
on the pilot's or copilot's EHSI's. When NAV Source
Selector is set to radio position, the TACAN radio is
tuned to a TACAN station and the radio is supplying
valid navigational data. TACAN or DME distance
information is displayed on the pilot's and copilots
EHSIs in the upper right-hand corner of the displays.
The system is protected by a 2-ampere circuit breaker,
placarded TACAN, located on the overhead circuit
breaker panel, Figure 2-16.
b. DME Hold Switch. A push-on/push-off
switch, placarded DME HOLD PUSH/SW, located on
the audio control panel T2 and right of the radio call
sign placard T1 , controls selection of the DME hold
function. When the DME HOLD switch is pushed to
the on position, the DME/TACAN distance frequency
in the DME/TACAN receiver/transmitter will be held
constant regardless of the frequency selected on the
NAV 1 control unit. The DME HOLD switch will
illuminate when the DME hold function is selected and
will be extinguished when the DME hold function is
deselected. The DME HOLD switch is inoperative
when the NAV/TA C is in the TAC mode or if the FMS
is controlling the DME.
3C-23. ADF RECEIVER (KDF-806).
a. Description. Two ADF navigation receivers
are installed to provide a visual indication of the
relative bearing to a selected ground radio station.
The units are airborne low frequency radio direction
finders that receive signals from transmitters in the 190
to 1799 kHz range, and the international distress
frequency of 2182 kHz. The ADF receiver can also be
used for homing and position fixing. The ADF receiver
is equipped with a Beat Frequency Oscillator (BFO)
which is used to more accurately tune weak signals.
Reception distance of reliable signals depends upon
the power output of the transmitting station and the
atmospheric conditions. Bearing information from the
number 1 ADF receiver may be displayed visually by
the single-needle pointer on the pilot's and copilot's
EHSI. Bearing information from the number 2 ADF
receiver may be displayed visually by the double-
needle pointer on the pilot's and copilot's EHSI. ADF