c. On the Spectrum Analyzer, set the Span/Div ot
50 kHz per division.
d. On the computer keyboard, use the ‘, 1, 2, and
3 keys to increment and the 7, 8, 9, and 0 keys
to decrement the value of the DAC’ssetting.
Start the calibration by pressing an increment
key.
e. While observing the first Bessel null (Figure
4-16) on the Spectrum Analyzer display,adjust
the value of the DAC’ssetting to reduce the
carrier level as low as possible.
f. When finished setting the DAC, press Qon the
keyboard.
The program will exit to the $prompt.
g. Record step completion on the Test Record.
7. Store the calibration data as follows:
a. At the $prompt, type: calterm 787 and
press <ENTER>. (The $prompt will appear on
the screen when the calibration data has been
stored.)
b. Record step completion on the Test Record.
4-56 682XXB/683XXB MM
PHASE MODULATION
CALIBRATION (FM) CALIBRATION
NOTE
You may need to adjust the RBW
settingon the Spectrum Analyzer in
order to see the >–40 dBc null.
CAUTION
Whensaving calibration data, turn-
ing off the instrument before the $
prompt returns to the screen can
cause all stored data to be lost.