34-31-02
ú ú 01 Page 1 ú Jul 15/93
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
F. Frequency selection is controlled from the control panel. The G/S portion of the unit becomes operative only when a localizer frequency is selected. Localizer frequencies extend from 108.10 to 111.95 MHz, with 40 channels spaced at 50 kHz on the odd tenths megahertz and the odd tenths megahertz plus 50 kHz. Glide slope frequencies range from 329.15 to 335.0 MHz and are paired with the localizer frequencies as shown in Fig. 2. VOR frequencies also spaced at 50 kHz, extend from 108.00 to
117.95 MHz except for the localizer frequencies.
G. In VOR operation, two signals (30 Hz REF and 30 Hz VAR) as radiated by a VOR ground station are processed by the navigation unit to produce the station bearing, VOR deviation and to/from signals. The to/from signal outputs of the VHF navigation units are not used. The to/from signals are generated within the flight management computer system (FMCS) (AMM 34-62-01/001) for display on the EHSI's. In LOC operation, the deviation signal is produced by a comparison of the amplitude difference between two tone modulated signals (90 Hz and 150 Hz) as radiated by a runway localizer transmitter. Portions of these signals are summed to produce the warning flag signals. The G/S deviation signals are produced in much the same manner as the LOC deviation signals.
2. Navigation Unit_______________
A. Two navigation units (VOR/ILS receivers) are installed in electronic equipment rack E3-4. The receivers employ 2-out-of-5 binary switching for frequency selection. These units process VOR, localizer and glide slope signals and provide output of ground station bearing course deviation, and warning flag valids for the RDDMI's, the DFCS, the EFIS, and the GPWS.
B. Collins 51RV Series Receiver
(1)
Each receiver contains circuit boards and an interconnect unit. The circuit boards consists of VOR/LOC and glide slope receiver assemblies with associated instrumentation, digital instrumentation and self-test circuit board assemblies, an RMI driver and a power supply.
(2)
The chassis provides the mounting surfaces for connectors, support for two swing-out mounting frames, and a center mounting board.
(3)
The center mounting board consists of a removable printed circuit board that contains the power supply, audio amplifier, and RMI driver circuits.
(4)
The left swing-out mounting frame supports the VOR/LOC receiver board and the glide slope receiver board. Each board contains tuner, synthesizer, self-test, and injection oscillator circuits. The VOR/LOC receiver is on the outer board and the glide slope receiver is on the inner board.
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