HP 8642A - Page 294

Performance Tests
4-44
PERFORMANCE TESTS
3. Set up the Spectrum Analyzer as follows:
VIDEO
BW
SWEEP TIME
ATTENUATION
RESOLUTION
CENTER FREQ.
SPAN
REFERENCE LEVEL
1Hz
5.0 sec
o dB
10Hz.
Foff
o Hz
-50 dBm
4. Record the level of the F off peak signal for later use.
NOTE
Model 8642A/B
It may be necessary to fine tune the spectrum analyzer
center frequency adjustment. The spectrum analyzer
band width will be centered when the maximum signal
level is obtained while tuning the center frequency
adjustment.
5. Set the HP 8642 to FRF then 0 dBm amplitude by incrementing the
amplitude in 10 dB steps.
Use the oscilloscope to verify that no large AC signal is
present. If AC is present the mixer input signals are not
at the same frequency and spectrum analyzer damage
may result.
6. On the HP 8642, enter SPCL 250. View the signal in the dc coupled
mode on
the oscilloscope. Use the HP 8642 knob to adjust the dc
level on
the oscilloscope as close to zero as possible. This sets the two
input signals to the mixer in phase quadrature (90 degrees out of
phase).
7. View the trace and note the average noise level.