(2)  verify that the transponder replies to at least 90 percent of ATCRBS interrogations when the amplitude of the P2 pulse is 9 dB less than the P1 pulse. If the test is conducted with a radiated test signal, the interrogation rate shall be 235 ±5 interrogations per second unless a higher rate has been approved for the test equipment used at that location.

(e) Receiver Sensitivity -

(1) verify that for any class of ATCRBS Transponder, the receiver minimum triggering level (MTL) of the system is -73 ±4 dbm, or that for any class of Mode S transponder the receiver MTL for Mode S format (P6 type) interrogations is -74 ±3 dbm by use of a test set either -

(i)     connected to the antenna end of the transmission line;

(ii) connected to the antenna terminal of the transponder with a correction for 

             transmission line loss; or

(iii) utilized radiated signal.

(2) Verify that the difference in Mode 3/A and Mode C receiver sensitivity does not exceed 1 db for either any class of ATCRBS transponder or any class of Mode S transponder.
 

(f) Radio Frequency (RF) Peak Output Power -

(1) Verify that the transponder RF output power is within specifications for the class of transponder. Use the same conditions as described in (c)(1) (i), (ii), and (iii) above.

(i)    for Class 1A and 2A ATCRBS transponders, verify that the minimum RF peak 

           output power is at least 21.0 dbw (125 watts);

(ii)   for Class 1B and 2B ATCRBS Transponders, verify that the minimum RF peak  output power is at least 18.5 dbw (70 watts);

(iii) for Class 1A, 2A, 3A, and 4 and those Class 1B, 2B, and 3B Mode S transponders that include the optional high RF peak output power, verify that the minimum RF peak output power is at least 21.0 dbw (125 watts);

(iv) for Classes 1B, 2B, and 3B Mode S transponders, verify that the minimum RF peak output power is at least 18.5 dbw (70 watts);

(v)    for any class of ATCRBS or any class of Mode S transponders, verify that the maximum RF peak output power does not exceed 27.0 dbw (500 watts).
 
 Note: The tests in (e) through (j) apply only to Mode S transponders.

(g) Mode S Diversity Transmission Channel Isolation: For any class of Mode S transponder that incorporates diversity operation, verify that the RF peak output power transmitted from the selected antenna exceeds the power transmitted from the non-selected antenna by at least 20 db.

(h) Mode S Address: Interrogate the Mode S transponder and verify that it replies only to its assigned address. Use the correct address and at least two incorrect addresses. The interrogations should be made at a nominal rate of 50 interrogations per second.

(i) Mode S Formats: Interrogate the Mode S transponder with uplink formats (UF) for which it is equipped and verify that the replies are made in the correct format. Use the surveillance formats UF = 4 and 5. Verify that the altitude reported in the replies to UF = 4 are the same as that reported in a valid ATCRBS Mode C reply. Verify that the identity reported in the replies to UF = 5 are the same as that reported in a valid ATCRBS Mode 3/A reply. If the transponder is so equipped, use the communication formats UF = 20, 21, and 24.

(j) Mode S All-Call Interrogations: Interrogate the Mode S transponder with the Mode S only all-call format UF = 11, and the ATCRBS/Mode S all-call formats (1.6 microsecond P4 pulse) and verify that the correct address and capability are reported in the replies (downlink format DF = 11).

(i) ATCRBS Only All-Call Interrogation: Interrogate the Mode S transponder with the ATCRBS only all-call interrogation (0.8 microsecond P4 pulse) and verify that no reply is generated.
　
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