519 
23-21-01 Page 502  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Nov 15/77 

D.  Test VHF Transceiver
(1)  
Connect headset and microphone to VHF transceiver on electronic equipment rack E2.

(2)  
Press SQUELCH DISABLE button on transceiver. Listen for receiver noise.

(3)
Release button and check that noise cuts off.

(4)  
Press microphone PTT button. Check that TRANSMIT MONITOR light comes on.

(5)  
Talk into mike and listen for sidetone in headset. Check that TRANSMIT MONITOR light varies in intensity with modulation. Release PTT button.

(6)  
Secure VHF systems.

(7)  
Determine whether there is any further need for electrical power on the airplane; if not, remove external power.

504 
Feb 15/81  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  23-21-01 Page 503 

VHF ANTENNA - REMOVAL/INSTALLATION
1.  Equipment and Materials
A.  Cleaning solvent (Ref 20-30-31, Cleaners and Polishes)
B.  Gauze
C.  Aerodynamic smoother (Ref 20-30-11, Sealants and Sealing Material)
2.  Remove VHF Antenna (Fig. 401)
A.  Remove aerodynamic smoother around the antenna base.
B.  Remove 10 mounting screws from antenna base.
C.  Separate antenna from airplane.
D.  Tilt antenna to one side and expose antenna electrical connector and cable on aft end of antenna base.
NOTE: On upper antenna, secure cable so that it cannot fall into airplane.
E.  Disconnect antenna from connector.
F.  Remove O-ring.
3.  Prepare to Install VHF Antenna
A.  Clean antenna base and antenna mount on fuselage with cleaning solvent.
B.  Dry and remove any traces of dust and solvent with clean dry gauze.
C.  Apply water resistant compound to mating surfaces (Ref 51-21-91, Cleaning/Painting).
D.  Check O-ring; if damaged, replace with new O-ring.
4.  Install VHF Antenna
A.  Install O-ring.
B.  Connect connector to antenna and tighten securely.
C.  Tilt antenna into position; install 10 mounting screws and tighten.
D.  Apply aerodynamic smoother (sealer) around antenna base.
E.  Conduct bonding check (Ref 23-21-11, Inspection/Check).
535 
May 1/75  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  23-21-11 Page 401 

H34222
 VHF Antenna Installation  500 
23-21-11Page 402   Figure 401 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Feb 15/68 

VHF ANTENNA - INSPECTION/CHECK
1.  General
A.  The following bonding check should be conducted any time that a VHF antenna has been reinstalled (Ref 23-21-11 R/I).
2.  Equipment and Materials
A.  Bonding Meter (Ref 20-22-01)
3.  Check VHF Antenna Bonding
A.  Measure dc resistance between antenna base and fuselage structure per 20-22-01. Resistance should not exceed 0.1 ohm.
500 
Feb 20/85  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  23-21-11 Page 601 

SELCAL SYSTEM - DESCRIPTION AND OPERATION
1. General
A.  Two identical selcal (selective calling) systems are installed in the airplane. A four-tone alert signal from a ground station, is sent to an airplane VHF or HF system and is detected by the selcal system. The selcal system alerts the crew members by means of a light and a chime whenever a message is to be received on one of the communication systems.
B.  The selcal systems are composed of a decoder, chime, and selcal control panel. The decoder is located in electronic equipment rack (E2-2). The chime is enclosed within the aural warning unit on the forward right side of the control stand. The selcal control panel is installed on the pilots aft overhead panel. See Fig. 1 for the component locations.
C.  Selcal system No. 1 obtains 28 volts dc from switched electronics bus No. 1 on circuit breaker panel P18. Selcal system No. 2 obtains 28 volts dc from switched electronics bus No. 2 on circuit breaker panel P6.
2.  Control Panel
A.  On GJ B-2509 thru B-2510 and B-2524, the control panel has two indicator lights and a PUSH-TO-RESET button Selcal-1 indicator light will come on when decoder unit No. 1 is activated; and selcal-2 light responds to decoder unit No. 2. When pressed the PUSH-TO-RESET button deactivates both decoders simultaneously.
　
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