Giga-tronics GT 9000, Operation & Maintenance Manual

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A.15.4 Option 27 Acceptance Test Procedure (Linear AM Mode)
1. Select LIN AM EXT: ON.
2. With an ohmmeter, measure the resistance of the AM input BNC to ground; it should
read 50
Ω
,
±
3
Ω
.
3. Connect the GT 9000 RF output to a mixer box, as shown in Figure A-2. On the
HP 8902A, select 50 Hz and 15 kHz filters, AM mode. Set the GT 9000 RF output
frequency to 5 GHz. Using a BNC T connector and oscilloscope, apply a 1.0 Vpp, 1 kHz
sine wave to the AM input BNC on the GT 9000 front panel.
4. Measure the percentage of distortion at 1 kHz; verify that the distortion is < 10%
(typical).
5. Disconnect external modulation. Select LIN AM SIN: ON, at a 1 kHz rate and 50%
depth. Using the HP 8902A, measure AM%. Verify a modulation reading of 45 to 55%.
Re-check at 20% depth; verify a modulation reading of 15 to 25%. Re-check at 80%
depth; verify a modulation reading of 75 to 85%.
6. Select LIN AM SQR: ON, 50% depth. Turn off all filters on HP 8902A. Verify an AM%
reading of 45 to 55% on the HP 8902A.
7. Select LIN AM TRI: ON, 50% depth. Turn on 50 Hz and 15 kHz filters on HP 8902A.
Verify an AM% reading of 45 to 55% on the HP 8902A.
8. Connect a detector to Model GT 9000 RF out. Connect the detector output to the
oscilloscope (channel B, 50
Ω
on). Set the scope to 2 mV and 200
µ
sec.
9. Select LIN AM EXT: ON.
10. Apply a 1 Vpp, 1 kHz sine wave to the AM input BNC. Adjust the channel B input
vernier for a display of the waveform that spans six vertical divisions.
11. Adjust the external modulation rate for 10 Hz; verify that the displayed waveform has
an amplitude of >4 divisions on the scope. Vary the rate from 10 Hz to 50 kHz, and
verify that the waveform amplitude maintains an amplitude of >4 divisions.
Model GT 9000 Microwave Synthesizer
A-16
Manual No. 120AM00250, Rev C, September 1998