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 ADF -------- ADF receiver automatically determines the bearing to the
selected station. Both the loop and sense antenna circuits
operate.
 TEST ------- Receiver perform an ADF system self-test. This position is
the only momentary position of the switch.
(2) ADF 1 and ADF 2 audio gain control ------ the gain control is used as an
audio gain control .
(3) ADF 1 and ADF 2 receiver tuning controls ------- The frequency is selected
by concentric knobs. The outer knob controls the 1000 and 100 KHz portion of
the operating frequency. The next knob controls the 10 KHz and the inner knob
controls the 1KHz and 0.5 KHz portion of the operating frequency. The
frequency is displayed in the frequency window (ADF 1and ADF 2 tuning
indicator ) above the frequency controls .
(4) The tone 1 or 2 switch is a 3-position switch that controls the operation of
the 1020Hz tone oscillator in the ADF receiver. This tone may be used to check
the audio from the ADF receivers and as a beat frequency oscillator for
continuous wave station.
[4] The ADF receiver processes signals in the 290KHz through 1749.5 KHz
frequency band. Audio and bearing to a ground station are provided by the
receiver, on the front of the receiver, there are 2 connectors. ------- one is the
sense antenna connector, the other is loop antenna connector.
[5] The loop antenna is a sealed, non-rotating antenna consisting of two pairs of
ferrite core coils. One pair is aligned parallel to the longitudinal axis of the
airplane; the other pair is aligned parallel to the lateral axis . The coils interface
with the ADF system through a single connector on the top of the antenna.
Fig. 28-3 loop antenna and QEC
The loop antenna is designed to accept the magnetic component of the received
electromagnetic wave for use in the ADF system. The Quadrantal error corrector
(QEC) compensates for the distortion to the loop antenna's reflection pattern
caused by the airplane's wings , engines , and fuselage. The device then couples
the RF signals from the loop antenna to the antenna cable. Access to the loop
antenna is gained by first removing eight screws which fasten the antenna cover
to the airplane. The corrector is accessed by first removing the loop antenna.
[6] The sense antenna is an omnidirectional antenna designed to accept the
electric component of the received electromagnetic wave for use in the ADF
system. The sense antenna coupler matches the capacitance of the ADF sense
antenna to the capacitance of the transmission line between the antenna and the
receiver.
Fig. 28-4 sense antenna and coupler
[7] The sense antennas are installed on the left and right wing to body fairings,
behind the aft wheel well bulkhead. The couplers are mounted to the aft
bulkhead of the left and right main wheel well. The sense antenna is part of the
reinforced wing to body fairing that has been flame sprayed with aluminum.
This metal coating is used as the antenna element.
[8] The RDDMI (radio direction distance magnetic indicator ) displays VOR or
ADF bearing information. The display function is selected by operating
ADF/VOR mode selector switches.
Fig. 28-5 ADF indicator
[9] The No. 1 radio bearing pointer is the single line pointer that displays
VOR-1 or ADF-1 bearing information. The No.2 radio bearing pointer is the
double line pointer that displays VOR-2 or ADF-2 bearing information. The
pointer mode switches are push-on, push-off types and determine whether the
pointers are controlled by ADF or VOR information. When the pointer is
switched to the ADF mode, the ADF legend and the associated arrow come into
view. The arrows are miniature representations of their respective radio pointers.
The legend color is the same as the color of the radio pointers . The pointer
warning flags come into view when power is removed from the ADF receiver.
[10] The EHSI may be used to display ADF bearing pointers in NAV, VOR/ILS,
and PLAN mode. It may also be used to display ADF bearing vectors in the
MAP and CTR MAP mode.
EXERCISE
A. Find out the explanations of the following words in your "English-chinese
technical dictionary"
1. non-directional beacon [P1-106 ]
2. capacitance [ P1-26 ]
3. capacitor [ P1-26 ]
B. Translate the first, fifth and sixth paragraphs of lesson 28 into chinese.
C. According to Fig.28-2, describe the functions of the ADF control panel (in
chinese).
READING MATERIAL
LESSON 29
WEATHER RADAR
VOCABULARY
1. WXR = weather radar [ 'weð ]['reida: ] 氣象雷達
2. moisture-laden [ 'm ist ]['leidn ] 充滿水分的
3. formation [ f :'mein ] n. 結構;形成物
　
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