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the VOR antenna is accessible by removing the vertical fin tip.
5. Localizer Antennas__________________
A. Two localizer antennas are installed in the nose radome. Both antennas are dual receiving units. One antenna is mounted above the weather radar unit. The other is mounted below the weather radar antenna. The outputs of the localizer antennas are fed to the VOR/LOC antenna switches.
6. VOR/LOC Antenna Switches________________________
A. Five antenna switches, installed behind the VOR/ILS receivers on shelves El-2 and El-3 of the main equipment center, select either the VOR antenna or the localizer antenna as an rf source for the associated VOR/ILS receiver. The switches operate in the 108- to 118-MHz frequency range. Switching is accomplished by changing the characteristics of a tuned line network to match input and output impedances for signal transfer. A fail-safe (power off) characteristic of the antenna switches connects the localizer antenna to the VOR/ILS receiver.
7. Glide Slope Antennas____________________
A. On XA ALL EXCEPT AZ 221-229; SN 351-399; IB 406-499; and AT airplanes, a total of six glide slope antennas are installed in the aft nose gear wheel well doors. Each door cavity houses one track antenna, two cables. The track antenna is a tunable single element I-slot type installed in the door leading edge. The capture antennas are two element tunable antenna arrays installed in the outer side of each door parallel to the longitudinal axis. The hybrid within the door cavity provides impedance matching for combining the rf outputs of the two capture antennas. On AT ALL, a total of three glide slope antennas, two track and one dual capture, are installed. The track antennas are nontunable I-slot type units located one each on the leading edge of the aft nose gear wheel well doors. The capture antenna, also a nontunable unit, is located in the nose radome.
B. On AZ 221-299; SN 351-399; IB 406-499; a total of four glide slope antennas, two track and two capture are installed. The track antennas are nontunable dual element I-slot type units located one each on the leading edge of the aft nose gear wheel well doors. The capture antennas, also nontunable units, are located in the nose radome.
8. Glide Slope Antenna Hybrids___________________________
A. On XA ALL EXCEPT AZ 221-229; SN 351-399; IB 406-499; and AT airplanes, two additional 4-port type hybrid antenna couplers are installed at station 400. The station 400 hybrids combine the rf output of the track and capture antennas to provide a single glide slope rf input for the receivers.
9. Glide Slope Antenna Coaxial Relays (AZ 221-299; SN 351-399; IB 406-499;
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AT ALL)
EFFECTIVITY
AZ ALL
AT ALL
IB ALL CONFIG 2 SN ALL 02 Page 9 Aug 25/87
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A. Two coaxial relays are mounted one each on glide slope antenna switching panels P31 and P32. The coaxial relays are controlled by transistor switching logic in the primary and alternate landing gear logic units. The relays switch the glide slope rf signal from the nose radome capture antenna to the landing gear door track antenna when the landing gear is down. This eliminates spurious capture antenna signals which cause loss of glide slope capture when in track antenna configuration and the airplane is flown at high bank angles.
B. On AZ 221-299; SN 351-399; IB 406-499; a third coaxial relay for receiver No. 3 is installed on panel P31. Relay No. 3 is controlled by transistor switching logic in autopilot accessory box No. 3 and in the primary and alternate landing gear logic units (Fig. 5).
10. Glide Slope Antenna Test Switches and Annunciators
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A. On AT ALL, two glide slope antenna test switches and associated annunciators labeled G/S 1 ANT and G/S 2 ANT are installed on center instrument panel P2.
B. On AZ 221-299; SN 351-399; IB 406-499, three glide slope antenna test switches and annunciators are installed on center instrument panel P2.
11. Flight Instruments
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A. Radio Magnetic Indicator
(1)
On XA ALL EXCEPT AT airplanes, each of the captain's and first officer's instrument panels has an radio magnetic indicator (RMI) for display of VOR and DME data. Each RMI displays aircraft magnetic heading from the magnetic heading reference system (34-21-00) and VOR bearing. On AT ALL, each of the captain's and first officer's instrument panels have two radio magnetic indicators (RMI's) for display of VOR and ADF data. Each RMI displays aircraft magnetic heading from the magnetic heading reference system (34-21-00) and VOR or ADF bearing.
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