BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
(5) The right swing-out mounting frame supports board for interconnections and the remaining VOR/ILS circuits. The VOR/LOC instrumentation and 2 out of 5 circuits, and optional expanded VOR monitor, programmable bearing filter, and digital bearing output circuits are on the inner board. The glide slope instrumentation, digital instrumentation, and optional VOR/ILS self-test and expanded ILS monitor circuits are on the outer board.
3. VHF NAV Control Panel_____________________
A. The controls for each navigation unit are on separate NAV control panels. The controls on each panel consist of an AUTO/MAN mode select switch/indicator with associated liquid crystal frequency displays, two concentric frequency selector knobs, and two test switches.
B. The manual and automatic tuning modes are selected by the AUTO/MAN switch/indicator which illuminates to indicate the selected mode.
C. The frequency selector knobs provide manual tuning of the associated VOR/ILS navigation unit and the DME interrogator. The small knob controls the tenths and hundredths digits while the large knob controls the units and ten digits displayed by the MANUAL frequency display.
D. The MANUAL frequency display indicates VOR/ILS frequency channels spaced at 50 kHz between 108.00 and 117.95 MHz. A bar appears across the display while in the auto mode. The MANUAL frequency display can be preset to another frequency while in the auto mode by using the manual frequency selector knobs.
E. The AUTO frequency display is blank during manual mode of operation. In the AUTO mode, the display indicates frequencies between 108.00 and
117.95 MHz as programmed by the Flight Management Computer System (FMCS) (AMM 34-62-01/001). The AUTO frequency display indicates dashes during FMCS agility mode.
F. The frequency displays and AUTO/MAN mode annunciators are tested through the airplane lighting master dim and test circuits. When the master TEST switch is actuated, both AUTO/MAN mode annunciators illuminate and the frequency displays flash 188.88, alternating 2 seconds on and 1 second off.
G. The VOR -- DME TEST switch controls the VOR self-test mode for the VOR/ILS navigation unit or the self-test mode for the DME interrogator. In the VOR position, the switch completes the VHF NAV test interlock circuit for the FMCS.
H. The UP/LT -- DN/RT TEST switch controls the up/left and down/right ILS self-test modes for the VOR/ILS navigation unit. Positioning the switch to either ILS self-test position also completes the VHF NAV test circuit for the FMCS.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
4. VOR/LOC Antenna
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A. The VOR/LOC antenna assembly is integral with the fin cap installed on top of the vertical stabilizer. The fin cap has metallic leading and trailing edge tips mounted on a fiberglass shell to provide an aerodynamic surface. The antenna consists of two balanced half loops with a hybrid coupler added for increased reliability under fault conditions. The hybrid coupler is composed of two quarter wavelength lines with the dual outputs to the receivers shunted by a 100-ohm resistor. In addition, an 18.5-inch tuning stub is connected to each half loop. A lighting diverter strip is embedded along the top centerline of the antenna assembly.
5. Glide Slope Antenna
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A. The glide slope antenna with dual output ports is a horizontally polarized unit installed above the weather radar antenna in the nose radome.
6. Glide Slope Antenna Director Bar
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A. The glide slope (G/S) antenna director bar is a passive element of the glide slope antenna used to alter the G/S radiation patterns such that the navigation units have maximum glide slope sensitivity.
B. The bar consists of a 13-inch strip of aluminum foil, pressure sensitive tape, installed horizontally inside the nose radome approximately 22 inches forward of the aft edge of the nose radome top centerline.
7. Localizer Antenna
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A. A localizer antenna with dual rf output ports is installed in the nose radome below the weather radar antenna. The rf ports are connected to separate ILS relays to provide localizer rf to the navigation units.
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