HP 54710A - Page 334

Magnify span
The Magnify span softkey is displayed when Magnify is set to on. The
Magnify span softkey uses software expansion to zoom in on the FFT record.
The range of values is from the unmagnified span value to 1/200th of the
unmagnified span in steps of 1, 2, and 5. You can enter any magnification
span in that range from the keypad.
Center freq
The Center freq softkey is displayed when Magnify is set to on. The Center
freq softkey uses software expansion to center the frequency record to the
desired frequency.
Scale
The Scale softkey uses software expansion to set the vertical scaling of the
FFT function. It does not affect the hardware settings in the plug-ins. The
scaling units are in dB per division. For example, if the scale is set to
10 dB/div, and a peak is two divisions high, you know that the amplitude of
the frequency peak is 20 dB.
Offset
The Offset softkey uses software expansion to move the FFT function
vertically on the screen. Offset is the value at the center of the graticule
area. If you adjust the offset so that a peak is at the vertical center of the
graticule area, then you know that the peak magnitude is the offset value.
For example, if the peak of the spike is at the vertical center of the graticule
area and the offset reading is
−
16.2 dBm, then you know that the peak
magnitude is
−
16.2 dBm.
FFT Menu
FFT Scaling
21–7