Figure 2-1. Direction Finder Control C-6899/ARN-83, controls and indicators.
c. Allow direction finder set to warm up for 5
22. Modes of Operation
minutes. See that the panel, tuning meter, and
a. The control unit function switch enables the
FREQUENCY window arc illuminated.
selection of three operating modes: ADF mode for
automatic direction finding, homing to a radio sta-
2-4. Adf Operation
tion, and position fixing; ANT (antenna) mode for
a. Homing to Radio Station (fig. 2-2). W h e n
radio range navigation or use as a radio broadcast
homing to a radio station, the aircraft bearing indi-
station receiver; and LOOP mode for manual direc-
cater pointer indicates the magnetic bearing" of the
tion finding or when using aural null for homing and
station and the pilot uses his rudder to fly on this
position fixing. In any operating mode, the direc-
heading and home to the station. Normally, t h e
tion finder set will provide an aural output of any
pilot would maneuver the airplane to hold the bear-
audio modulating the radio station rf carrier. A
ing indicator pointer under the lubber line. If there
beat frequency oscillator (bfo) aids in tuning for
is a crosswind, the airplane must crab into the wind
zero beat or supplying audio for continuous-wave
and fly a curved and longer flightpath. In figure
(cw) signals.
22, the solid line is the track and bearing to a radio
b. Refer to the following to operate the equip-
station if no crosswind exists. The dotted line is the
ment in any particular mode:
actual flightpath with a crosswind from the right.
(1) Preliminary operating procedure (para
To correct for wind, the pilot must fly into the wind
on a heading that will hold the bearing shown in
(2) Adf operation (para 2-4).
(3) Antenna operation (para 2-5).
station as follows:
(4) Loop operation (para 2-6).
(1) Set control unit function switch to ADF
and allow 5 minutes for warmup.
2-3. Preliminary Operating Procedure
(2) Set BFO-OFF switch to OFF.
a. Turn on aircraft radio equipment power con-
(3) Set range switch to the frequency range of
trols.
a radio range station, an outer marker, or
a broadcast station. The range selected
b. Set control unit function switch for desired
type of operation (paras 2-4, 25, and 2-6).
will appear in the FREQUENCY window.
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