159, 172-182, 185-199; SN 301-350; IB 405; GN ALL; CONFIG MD ALL; VM ALL 02 Page 1
Sep 25/94
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SEE A (2 PLACES) SWITCH AND WAVEGUIDE (IF INSTALLED) DUMMY LOAD RECEIVER/ TRANSMITTER ANTENNA WEATHER RADAR
(IF INSTALLED) REFLECTOMETER WAVEGUIDE ASEE RECEIVER/ TRANSMITTER (2 PLACES)
PASSENGER 1
WEATHER RADAR ANTENNA
WAVEGUIDE SWITCH WAVEGUIDE
FREIGHTERS 2
RADIATOR ANTENNA FLAT PLATE
SEE C
SEE B
1
AF 101-116,172-173,181,182,191-199;
SN 301-350; IB 405; GN ALL; MD ALL; VM ALL
2 AF 151-159
Weather Radar System Component Location Figure 1 (Sheet 1)
EFFECTIVITY
AF 101-120,123-156,158,159, CONFIG 2 172-182,185-199; SN 301-350; 799 Page 2 IB 405; GN ALL; MD ALL, VM ALL Sep 25/94
34-43-00
RECEIVER/TRANSMITTER
(PANEL FACE VEIW)
INDICATOR
Weather Radar System Component Location
Figure 1 (Sheet 2)
EFFECTIVITY AF 101-120,123-156,158,159,
CONFIG 2 172-182,185-199; SN 301-350; 799 Page 3IB 405; GN ALL; MD ALL; VM ALL Sep 25/94
34-43-00
2. Control Panel
_____________
A. The control panel has illuminating pushbutton switches to allow mode selection. The pushbuttons are mechanically interlocked such that only the last pushbutton pressed has effect on mode selection.
B. A system transfer switch allows selection of system 1 or 2. A tilt control, calibrated in 1-degree increments, allows the antenna system to be tilted UP or DN (down) through 15 degrees (in each direction). Receiver sensitivity is controlled by a GAIN-control potentiometer/switch, which may be in the normal automatic gain (AGC) position or switched manually to any desired gain between the MIN and MAX positions of the potentiometer.
C. A fault light on the panel indicates when an antenna fault or R/T fault has occurred. In the test mode, the light bulbs are tested.
D. A GND TEST/NORMAL switch is provided on the panel. The GND TEST position causes the waveguide switch at the R/T to direct rf output of the R/T into a dummy load. This allows normal operating mode selection and activation/test of the R/T transmitting section without radar pulse transmission from the antenna.
3. Receiver/Transmitter
____________________
A. On Passenger airplanes, two weather radar/transmitter (R/T) units are installed in a dual R/T mount located on the electronics equipment center rack E5. Access to the R/T is gained through the right crawlway that extends forward of the main electronics equipment center.
B. On Freighter airplanes, two weather radar receiver/transmitter (R/T) units are installed in two single R/T mounts located on the centerline of the compartment floor in the nose cargo door section.
C. Each R/T unit has a blower fan in the front and rear. Two test lamps, two annunciators, and three pushbutton switches on the front panel of each R/T assist in isolating faults during maintenance testing. Another switch tests the R/T front panel light bulbs, and two switches turn the modulator off (MOD OFF) and on (MOD ON) for maintenance.
D. The R/T contains a magnetron transmitter, modulator, duplexer, receiver, stabilization, power supply, and control circuits. The modulator is solid-state, using silicon-controlled rectifiers (SCR's) and saturable transformers to perform the switching functions. Additional circuits protect all solid-state devices against such faults as magnetron arcing, short circuiting, open circuiting, SCR lock on, and loss of trigger.
E. The duplexer circuits are solid-state. To isolate the receiver from the transmitter, high power ferrite circulators are employed. High energy pulses from a nearby radar set can not damage the receiver, as a detector circuit holds the duplexer in the transmit mode until the energy level of the nearby radar set falls to a safe level.
F. The receiver is a single conversion superheterodyne. The balanced mixer has low noise mixer diodes, and a solid-state local oscillator is employed. A constant noise level is held at the receiver output by an automatic sensitivity control circuit, which samples the receiver output level just before the transmitter pulse.
EFFECTIVITY
AF 101-120, 123-156, 158,
159, 172-182, 185-199; SN 301-350; IB 405; GN ALL; CONFIG MD ALL; VM ALL 02 Page 4
Sep 25/94
34-43-00
115V AC
NO. 2
