Fluke 6080A - Page 214

TROUBLESHOOTING AND REPAIR
FREQUENCY AND PHASE MODULATION
16. Set the UUT to SPCL 909, 800 MHz, 150-kHz dev, 25-Hz mod rate, INT ACFM.
Connect the oscilloscope to the 8901A MOD OUT. Adjust the scope for almost
full scale display with one cycle. Adjust R88 for a smooth waveform.
17. Set the UUT to 800 MHz, 5-kHz mod rate, 200-kHz dev, INT ACFM. Set the
8901A to FM, + peak, 300 Hz HP, 15 kHz LP. Adjust R141 for a 8901A reading of
200 kHz ± 1 kHz. Adjust R119 for symmetrical plus and minus readings about 200
kHz ± 1 kHz.
Repeat until both specs are met.
18. Set the UUT to 200 MHz, 5-kHz mod rate, 200-kHz dev, INT ACFM. Set the
8901A to FM, + peak, 300 Hz HP, 15 kHz LP. Adjust R140 for a 8901A reading of
200 kHz ± 1 kHz. Adjust R117 for symmetrical plus and minus readings about 200
kHz ± 1 kHz.
Repeat until both specs are met.
19. Set the UUT to 50 MHz, 5-kHz mod rate, 200-kHz dev, INT ACFM. Set the
8901A to FM, + peak, 300 Hz HP, 15 kHz LP. Adjust R139 for a 8901A reading of
200 kHz ± 1 kHz. Adjust R115 for symmetrical plus and minus readings about 200
kHz ± 1 kHz.
Repeat until both specs are met.
20. Set the UUT to 800 MHz, 70-Hz mod rate, 5-rad dev, INT ACFM. Set the 8901A
to øM, + peak, 15 kHz LP (all other filters removed), Avg and 70.7%. Adjust R145
for 5 rad.
21. Set the UUT to 800 MHz, 10-kHz mod rate, 5-rad dev, SPCL 721, INT ACFM.
Set the 8901A to øM, + peak, 300 Hz HP, >20 kHz LP. Adjust C75 for a 8901A
reading of 5 rad.
Set the UUT to 1-kHz mod rate. The 8901A reading must be 5 rad ± .05 rad.
22. Set the UUT to 800 MHz, 70-Hz mod rate, 5-rad dev, SPCL 721, INT ACFM. Set
the 8901A to øM, + peak, no filters, Avg and 70.7%. Adjust R146 for 5 rad. Set
UUT to SPCL 720.
23. Connect the 8840A to TP12 and adjust R49 to 0V DC.
Connect the 8840A to TP9. Verify that the 8840A reads between -3V DC and + 10V
DC.
24. Set the UUT to SPCL 909, 800 MHz, -5 dBm, mod freq 10 Hz, 25-kHz FM
deviation, SPCL 711, SPCL 752. Set the spectrum analyzer to IP, center freq
800.06 MHz, span 100 kHz, ref level -5 dBm, resolution bandwidth 30 kHz, video
bandwidth 30 kHz, sweep time 200 ms, log scale 6 dB, trigger free run.
Set the UUT to INT FM. Set analyzer to span 0 Hz, trigger video. Verify that the
droop of the demodulated FM is less than 10%. Set the UUT to EXT DCFM.
Verify that the droop of the demodulated DCFM is less than 2%.
6E-16