34-31-00
 ALL  ú ú 04 Page 8 ú Feb 15/99
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

 3.  VOR/LOC Antenna
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 A.  One dual-channel VOR/LOC antenna is used to provide rf signals to the ILS when the airplane is in the air prior to approach, and to the VOR system (Ref 34-51-00).
 B.  The VOR/LOC antenna is located on the vertical stabilizer tip. The left channel of the VOR/LOC antenna provides signals to the left ILS via the left VOR/LOC rf power divider. The right channel provides signals to the right and center ILS via the right VOR/LOC rf power divider and the right/center LOC rf power divider.
 4.  Localizer Antenna
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 A.  Two dual-channel LOC antennas are used to provide localizer information to the receivers when the airplane is in approach mode.
 B.  The LOC antennas are located on the forward pressure bulkhead inside the nose radome. One LOC antenna is located above and one below the weather radar antenna. The lower LOC antenna provides signals to the left and right ILS receivers. The upper LOC antenna provides signals to the center receiver. One channel of the upper antenna is not used.
 5.  Glide Slope Capture Antenna
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 A.  Two dual-channel G/S capture antennas are used to provide glide slope information to the receivers before the nose landing gear is down and locked.
 B.  The G/S capture antennas are located on the forward pressure bulkhead inside the nose radome below the weather radar antenna. The lower G/S capture antenna provides signals to the left and right ILS receivers. The upper G/S capture antenna provides signals to the center receiver. One channel of the upper antenna is not used.
 6.  Glide Slope Track Antenna
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 A.  Two dual-channel G/S track antennas are used to provide glide slope information to the receivers when the nose landing gear is down and locked.
 B.  The G/S track antennas are located in the leading edge of the aft wheel well doors for the nose gear. The left G/S track antenna provides signals to the left and center ILS receivers. The right G/S track antenna provides signals to the right receiver. One channel of the right antenna is not used.
 7.  VOR/LOC Antenna Switch
______________________
 A.  Three VOR/LOC antenna switches are used to switch each ILS receiver LOC input from the VOR/LOC antenna to the LOC antennas when the FCC is in approach mode.
 B.  The left, right, and center VOR/LOC antenna switches are located in the E1 electronics equipment rack in the main equipment center. They are located at the left end of the No. 6 shelf.
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 34-31-00
 ALL  ú ú 07 Page 9 ú Feb 15/99
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

 8.  Glide Slope Antenna Coaxial Relay
_________________________________
 A.  Three G/S antenna coaxial relays are used to switch each ILS receiver G/S input from the capture antenna to the track antenna when the nose landing gear is down and locked.
 B.  The left, right, and center G/S antenna coaxial relays are mounted on the antenna switching panel (P31) on the forward side of the STA 400 bulkhead.
 9.  VOR/LOC RF Power Divider
________________________
 A.  Three VOR/LOC rf power dividers are used to provide rf signals received by the VOR/LOC antenna to the ILS and the VOR system (Ref 34-51-00).
 B.  The VOR/LOC rf power dividers are located in the E1 electronics equipment rack in the main equipment center. They are located at the left end of the No. 6 shelf. One output of the left VOR/LOC rf power divider provides signals to the left VOR/LOC antenna switch. One output of the right VOR/LOC rf power divider provides signals to the right/center LOC rf power divider which in turn provides signals to the right and center antenna switches, respectively.
　
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