(f)
Disconnect test set.
(g)
Connect and reinstall ATC antenna (Ref 34-53-11).
(h)
Repeat steps (2)(a) thru (3)(g) for the alternate ATC system (if installed/required).
NOTE: Following tests will suffice for all but receiver sensitivity tests (Refer to NOTE preceding step D.(2)).
(i)
Perform steps (3)(a) and (3)(b).
(j)
Position controls on test set as follows: RCVR SENS - 65 REPLY/SLS - LEVEL 1090 MHz - 0 MODE - 3/A Power - ON. Check test set meter deflects full scale and readouts display FR1 and FR2 indicating a reply from the transponder.
(k)
On ATC control panel, rotate code selector knobs to any code desired. Verify test set numerical display indicates selected code.
CAUTION: DO NOT USE CODES 3100, 7500, 7600, 7700. THESE ARE EMERGENCY CODES.
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
(l)
On ATC control panel, activate IDENT. A decimal point should appear in test set display.
NOTE: If correct indications do not appear, it may be necessary to change position of test set to achieve sufficient signal strength. To assure that the test set antenna is coupling to the transponder antenna, the 1090 MHz control can be adjusted + or - from zero to adjust test set frequency to transponder frequency. Limit of adjustment is ± 6 MHz.
(m)
On ATC control panel, change code selection to code compliment. Compliment of test code is 7777 minus code being used. This checks full code capability of transponder.
EXAMPLE: If test code being used is 0340, compliment is:
7777
-0340
7437 compliment.
(n)
On test set, adjust RCVR/SENS control so meter deflection is about 1/4 scale. Adjust 1090 MHz control above and below 0 for MAXIMUM meter deflection. Maximum error permissible is ± 3 MHz.
(o)
On test set, position REPLY/SLS switch to 100% position. Test set meter now indicates reply rate as a percentage of interrogation rate, with full scale of 100%.
NOTE: A properly operating transponder must reply with a rate of 90% or greater.
(p)
To check SLS circuits of transponder, position test set REPLY/SLS switch to 10%/O dB. The meter, with full scale equal to 10%, should read 1.3% or less for a properly operating transponder. Note test set display extinguishes, indicating transponder is not replying to interrogations.
CAUTION: SOME TRANSPONDERS, WHEN RECEIVING A SIGNAL NEAR MTL (MINIMUM TRIGGERING LEVEL), MAY TRANSMIT A REPLY EVEN THROUGH SLS PULSE IS PRESENT IN INTERROGATION. IF A REPLY IS RECEIVED WITH SLS PULSE AT 0 DB, REPEAT SLS TEST WITH TEST SET PLACED CLOSER TO TRANSPONDER ANTENNA TO INCREASE SIGNAL STRENGTH.
(q)
Position test set SLS switch to -9 dB and READOUT switch to PILOT. Note presence of ATC code and framing pulses in display.
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(4) Perform altitude-reporting tests as follows:
WARNING: REFER TO PRECAUTIONS IN CHAPTER 34-11-0, PAGE 501 PRIOR TO OPERATING-PITOT-STATIC EQUIPMENT FOR THESE TESTS.
(a)
Position controls on test set as follows:
1) RCVR SENS - 65
2) REPLY/SLS - LEVEL
3) 1090 MHz - 0
(b)
On ATC control panel, select ALT RPTG and altitude source.
(c)
Connect pitot-static test kit to appropriate PITOT/STATIC systems.
(d)
Adjust appropriate altimeter to 29.92 inches of mercury.
(e)
On test set, position MODE switch to mode C, and READOUT switch to ALTITUDE. Hold POWER switch ON, readout windows should indicate field elevation as indicated by altimeter 75 feet.
NOTE: 1. READOUT switch may be changed to PILOT position and test set will indicate altitude transmission code for indicated altitude. READOUT selector may be placed in BINARY position and will indicate actual number of A-B-C-D pulses transmitted.
2.
The tester will add 400,000 feet to altitude if any invalid C pulses are present (CO - C5 - C7), 200,000 feet if any invalid D Pulses are present (D1 - D3 - D7), and 600,000 feet if both erroneous. C and D bits are present.
3.
When there is no Mode C information, such as would occur with a disconnected digitizer, test set altitude readout will be 4007. This can be verified by setting readout switch to PILOT. A display of 0000 will be indicated.
(f) Using air data test set and altitude reporting code list (Fig. 501), apply a static pressure to obtain a sufficient number of test altitudes (between 0 And 35,000 ft) to verify the following: 1) Binary code lines (A1 thru C4 and D4) between transponder and altitude source
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