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747-400 MAINTENANCE MANUAL
 S 865-370
 (25)
 Push the SETUP key on the test set and enter the appropriate range for the top and bottom antenna.

 S 735-197

 (26)
 Do a check of the DIVERSITY TEST.

 (a)  Make sure the test set shows PASSED and the DIVERSITY ISOLATION is  20dB.
 NOTE: To make sure the dynamic range is  20dB, do the
____ diversity test at a distance of less than 50 feet (15.2 meters) from the airplane's ATC antennas.
 S 735-198
 (27) Do a check of the MTL DIFFERENCE TEST.
 (a)  Make sure the Minimum Threshold Level (MTL) difference between mode A and mode C is  1.0dBm.
 S 865-371
 (28)
 Push the PWR TEST key on the test set.

 S 865-372

 (29)
 Use the SELECT key on the test set and select the bottom antenna.

 NOTE: Make sure the top ATC antenna is not in the line of sight of
____
 the test set antenna during the POWER TEST.

 S 865-373
 (30)
 Push the antenna push button switch.

 S 865-374

 (31)
 Slowly move the test set antenna 6 feet (1.8 meters) vertically from the ground, at less than 1 FT/SEC (30 CM/SEC).

 S 865-375

 (32)
 Push the antenna push button switch a second time to stop the test when the test set antenna is approximately 6 feet high.

 S 735-199

 (33)
 Do a check of the POWER TEST.

 (a)  Make sure the peak power output of the transponder is between 125W (EPR= 51.0 dBm) and not more than 500W (ERP = 57.0 dBm).
 NOTE: Effective Radiated Power (ERP) is the product of the
____ antenna output power and antenna gain.
 (b)  Make sure the Minimum Threshold Level (MTL) sensitivity is -74dBm (|3dBm).
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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A
747-400
MAINTENANCE MANUAL

 (c)  Make sure the test set shows PASSED for the BOT AVG (dBm).
 S 865-377
 (34)
 Insert the antenna shield over the bottom ATC antenna.

 S 865-378

 (35)
 Move the test set so that it is in the line of sight of the top ATC antenna.

 S 865-379

 (36)
 Push the SETUP key on the test set.

 (a)  
Enter the appropriate range for the top antenna.

 (b)  
Choose the top antenna on the SELECTED field.

 S 865-380
 (37)
 Push the PWR TEST key on the test set.

 S 865-381

 (38)
 Use the SELECT key on the test set and select the top antenna.

 S 735-382

 (39)
 Do a check of the POWER TEST.

 (a)  Make sure the peak power output of the transponder is between 125W (ERP = 51.0 dBm) and 500W (ERP = 57.0 dBm).
 NOTE: Effective Radiated Power (ERP) is the product of the
____ antenna output power and antenna gain.
 (b)  
Make sure the Minimum Threshold Level (MTL) sensitivity is -74 dBm (|3 dBm).

 (c)  
Make sure the test set shows PASSED for the TOP AVG (dBm).

 S 735-355
 (40) Do the system test again for the right or No. 2 ATC system.
 NOTE: On the test set, select the other ATC
____
 antenna.

 G. Put the Airplane Back to Its Usual Condition
 S 845-048
 (1)  
Remove the ATC ramp test set.

 S 865-383

 (2)
Remove the DO-NOT-CLOSE tags and close these circuit breakers:

 (a)  P7 Overhead Circuit Breaker Panel:
 1) 7F22, LANDING GEAR DSP & CONT PRI
 2) 7F23, LANDING GEAR DSP & CONT ALTN

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