User`s guide

b. Press (Bw) and decrease the resolution bandwidth using the Q) key, until measured signal
amplitude drops. Then press @) to increase the bandwidth until the signal amplitude
stops increasing and stays the same, or until the maximum resolution bandwidth is
reached. Use the narrowest bandwidth that does not cause a change in the signal
amplitude.
Note
As the resolution bandwidth is stepped down, the modulated signal must be
re-centered on the spectrum analyzer display. If this is not done, the signal
amplitude can decrease due to off tuning of the spectrum analyzer and not
because of the resolution bandwidth chosen.
For the best amplitude accuracy, the resolution bandwidth should be about 10 times
greater than the highest modulation frequency of interest.
For the 60 Hz fundamental, a 1 kHz resolution bandwidth works well. (For the HP 8591E,
HP 85933, HP 85943, HP 85953, and HP 85963, if harmonics are not a concern, a
100 kHz resolution bandwidth can be used and it will provide a faster update rate.)
c. Press Isw), VID BW AUTO MAN (MAN) and use the step keys to decrease the video
bandwidth until the amplitude of the measured signal drops. Then step the bandwidth
up until the signal amplitude stops increasing, or until the maximum video bandwidth is
reached. Use the narrowest video bandwidth that does not cause a change in the signal
amplitude.
For the best amplitude accuracy, the video bandwidth should be about 10 times greater
than the highest modulation frequency of interest.
For the 60 Hz fundamental, a 1 kHz video bandwidth works well.
‘7. Press [jJ and % AM ON OFF so that ON is underlined. The spectrum analyzer reads
out the percent AM of the largest modulation frequency. An arrow indicates the signal being
measured (see Figure 4-l). This measurement does not include all of the harmonics of the
modulating signal.
Note
The percent AM function will not run if the SIGNAL CLIPPED error message
is being displayed. Increase the reference level until the error message goes
away.
Note
Note
To return to the spectrum analyzer state prior to running the FFT function,
press the FFT OFF softkey. This turns off the FFT function. Press [RECALL],
INTERNAL +STATE , and 8 to recall the state from state register 8.
When the FFT measurement is active, pressing the [MEAS~USER] key will cycle
between the MEASUSER and FFT menus.
4-6 Making Measurements