HP 8901B

Model 8901B Operation
12.5 kHz
20 kHz
25 kHz
13. Decrease the LO frequency by an offset of either 8.25 kHz, 13 kHz, or 17 kHz depending on the
adjacent channel being measured (refer to the table below).
8.25 kHz
13 kHz
17 kHz
Channel Spacing in kHz
I
Displacement of the
6 dB Point per CEPT (in kHz)
1
14. The value displayed is the adjacent channel power measurement result.
To Measure the Upper Adjacent Channel Power
Setting Up the LO
1. 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
RF frequency Thing.)
2. Press the MHz key to manually tune and center the IF.
3. Select 24.0 SPCL to enter the Selective Power Measurement mode.
4. 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.)
5. Set the external LO source frequency to 455 kHz less than the input frequency and its amplitude
to
0 dBm.
a. If using the internal LO, on the Modulation Analyzer select 910 l) kHz. This tunes the
Modulation Analyzer to the image frequency of the
LO. At this time, the RF frequency
display will not match the input frequency value.
6. Key in 23.1 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
9 kHz and 4 kHz keys until the maximum value is displayed.
Measuring the Upper Adjacent Channel Power
12. Increase 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 corner need not be remeasured
when new measurements are made with that filter.)
rev.22DEC88
Selective Power Measurements (Option 030) 3-97