Anritsu 682XXB - Manual (Page 159)

When the DAC has been completely adjusted,
the program will exit to the
$
prompt.
g. Record step completion on the Test Record.
6. Internal Locked, Locked Low-Noise, and Un-
locked Narrow FM Mode Sensitivity calibration is
accomplished by adjusting the FM Variable Gain
Control DAC to reduce the carrier level as low as
possible at frequencies of 5 GHz and 20 GHz. The
modulating signal input is from the internal
Function Generator.
Perform the calibration as follows:
a. At the
$
prompt, type:
calterm 144
and
press <ENTER>.
b. On the Spectrum Analyzer, set the Span/Div to
50 kHz per division.
c. 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’s setting.
Start calibration by pressing an increment key.
d. While observing the first Bessel null (Figure
4-14) on the Spectrum Analyzer display, adjust
the value of the DAC’s setting to reduce the
carrier level as low as possible.
e. When finished setting the DAC, press
Q
on the
keyboard to go to the next calibration step.
When the DAC has been completely adjusted,
the program will exit to the
$
prompt.
f. Record step completion on the Test Record.
7. The FM Rear Panel Input Gain is calibrated to
balance the Locked and Unlocked Narrow FM
Mode Sensitivity obtained when the same exter-
nal modulating signal is applied to either the
front panel or rear panel FM input.
Perform the calibration as follows:
a. On the 682XXB/683XXB, disconnect the coax-
ial cable from the front panel FM IN connector
and connect it to the rear panel FM IN connec-
tor.
b. At the
$
prompt, type:
calterm 154
and
press <ENTER>.
682XXB/683XXB MM 4-49
FM
CALIBRATION CALIBRATION
NOTE
You may need to adjust the RBW
setting on the Spectrum Analyzer in
order to see the >–50 dBc null.