GTX 327 MAINTENANCE MANUAL
Page 5-9
190-00187-05
Rev. B
Pulse Width
Measure the pulse width of the detected pulse P1. The pulse width measured at the 50% point must be between
350 ns and 550 ns.
Pulse Rise Time
Measure the rise time of the detected pulse P1. The rise time measured from the 10% to 90% points must be
between 50 ns and 100 ns.
Pulse Fall Time
Measure the fall time of the detected pulse P1. The fall time measured from the 90% to 10% points must be
between 50 ns and 200 ns.
General Pulse Characteristics
Other than jitter that should not exceed 100 ns with respect to P3 with RF input levels of MTL+3 dB to
MTL+50 dB, the detected pulse waveform should be uniform and not exhibit any parasitic conditions.
With the ATC-1400A in Mode A with the PRF at 500 Hz, set the GTX 327 to squawk reply code 7777. Change
the F1/F2 Switch on the ATC-1400A to measure power between the first framing pulse (F1) and the last framing
pulse (F2) and verify that there is no more than 1 dB difference between measured peak power levels.
Transmitter RF Peak Power Output
Verify that RF peak power output is always greater than 125 watts through the calibrated –1.5 dB coax cable to
the ATC-1400A. Typical RF peak power output through the 1.5 dB coax is 150 watts which correlates to 212
watts peak at the rear of the unit.
Reply Transmission Frequency
Verify that the XMTR FREQ display on the ATC-1400A indicates 1087 MHz to 1093 MHz. Nominal setting is
1090
±
0.5 MHz.
If the transmitter frequency needs adjustment, perform the following steps:
1.
Remove DC power to the unit.
2.
Remove the GTX 327 unit cover and then remove the two screws that hold the receiver assembly.
3.
Fold the receiver assembly over the main board to provide access to the transmitter. Do not remove
the transmitter shield. An access hole is provided to adjust the transmitter frequency.
4.
Apply power to the unit and allow it to stabilize before adjusting. Do not adjust any other transmitter
adjustments.
5.
Adjust C525 for 1090 MHz.
The document reference is online, please check the correspondence between the online documentation and the printed version.