Nautel XR6, Operation And Maintenance Manual

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XR6/XR3 Operations and Maintenance Manual Test and adjustment
Page 5-4 Issue 3.1 2013-03-14
Non-standard adjustments
Complete the following non-standard adjustments only as directed by a troubleshooting or
replacement procedure in the
XR6/XR3 Troubleshooting Manual :
• RF drive symmetry
• Exciter Gain
• Modulation Peak Limiting
RF drive symmetry
Measure the symmetry of the RF drive being applied from the active RF synthesizer PWB to the RF
power modules as follows:
1. Select exciter A as the active exciter.
2. Connect an oscilloscope to BNC connector J5 [
RF DRIVE (TEST)
] on the RF drive buffer
PWB.
3. The oscilloscope should indicate a symmetrical (50% duty cycle) square wave with a nominal
amplitude of 15 V peak-to-peak.
4. Adjust exciter A's RF synthesizer PWB's
SYMMETRY
potentiometer (R32) to obtain a 50%
duty cycle.
5. If an external RF drive source is used, adjust the RF drive source to obtain a symmetrical
square wave. If necessary, adjust the external generator according to its maintenance manual.
6. Select exciter B as the active exciter. Repeat Step 3 through Step 5 for exciter B.
7. Disconnect the oscilloscope from J5 of the RF drive buffer PWB.