HP 8901B Operation And Calibration Manual page 210

Operation Model
8901B
PROCEDURE
The following procedures are examples of typical measurement applications. These procedures describe
the steps for measuring adjacent-channel power and single-sideband noise.
Adjacent Channel Power Measurements
Two procedures are available. The first procedure measures the lower adjacent channel power. The
second procedure measures the upper adjacent channel power.
To
Measure the Lower Adjacent Channel Power
Setting Up the LO
1.
2.
3.
4.
5.
6.
Tune to the input frequency. (Selecting the
FREQ
key automatically tunes the Modulation
Analyzer to the input frequency. Keying in the input frequency value (in MHz) followed by the
MHz key manually tunes the Modulation Analyzer to the frequency value keyed in. For more
information about tuning, refer to
R F
Fkequency
7hning.)
Press the MHz key to manually tune and center the
IF.
Select 24.0 SPCL to enter the Selective Power Measurement mode.
Select whether an external LO or the Modulation Analyzer's internal LO will be used. If the
internal LO will be used, go to step 7. If an external LO will be used, connect the LO signal source
to the LO INPUT connector on the rear panel of the Modulation Analyzer. (More information
about the LO INPUT is available in
LO Input
and
LO Output.)
Set the external LO source frequency to
455
kHz greater than the input frequency and its
amplitude to 0 dBm.
Key in 2 3 . 1 SPCL to set the LO to external.
Setting the Reference
7 . Select 24.1 SPCL to establish the
IF
reference value (in volts).
8. Select 24.2 SPCL to set the reference to 0
dB.
9. Adjust the LO frequency until the maximum value is displayed. The Modulation Analyzer's
automatic tuning capability measures an IF value close to the peak, but the internal circuitry
does not specifically check for a peak. This step enables you to fine tune to the peak of the signal.
a. If using an external LO, step the LO frequency in small increments until the peak value
b. If using the internal LO, set the desired increment value (in kHz) and step the LO using
10. Reselect 24.1 SPCL to establish the IF reference value (since that value has now been peaked).
11. Reselect 24.2 SPCL to set the reference to 0
dB.
is measured.
the
fi
kHz and JJ kHz keys until the maximum value is displayed.
Measuring the Lower Adjacent Channel Power
12. Decrease the
LO
frequency value until -6
dB
is displayed. Note the frequency difference between
the source and the LO. This frequency difference is relative to the 6
dB
corner of the IF bandpass
filter. (Once the 6
dB
corner frequency has been determined, the comer need not be remeasured
when new measurements are made with that filter.)
3-96 Selective Power Measurements (Option 030)
rev.22DEC88