Anritsu 682XXB, 683XXB 4-48 682XXB/683XXB MM

k. Now adjust the center frequency control to po-
sition the low (or high) carrier at the center of
the display.Note the frequency reading.
l. The difference between these two frequencies
should be 200 MHz ±0.5 MHz. If not, enter 2
and fine adjust the DAC to obtain this devia-
tion.
m.When finished setting the DAC, press Qon the
keyboard to return to the menu, then enter 3
to go to the next calibration step (adjusting the
DAC to obtain a 200 MHz deviation at
15 GHz).
When the DAC has been completely adjusted,
the program will exit to the $prompt.
n. Record step completion on the TestRecord.
5. External Locked, Locked Low-Noise, and Un-
locked Narrow FM Mode Sensitivity calibration is
accomplished by adjusting the FM VariableGain
Control DAC to reduce the carrier level as low as
possible at frequencies of 5 GHz and 20 GHz. The
modulating signal is from the external Function
Generator.
Perform the calibration as follows:
a. At the $prompt, type: calterm 125 and
press <ENTER>.
b. Set up the Function Generator for a 99.8 kHz
sine wave with an output level of 0.707 volts
RMS (2 volts peak to peak). Use a frequency
counter to verify the output frequency of your
function generator is set to ±1%.
c. On the Spectrum Analyzer, set the Span/Div to
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 calibration by pressing an increment key.
e. While observing the first Bessel null (Figure
4-14) 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 to go to the next calibration step.
4-48 682XXB/683XXB MM
FM
CALIBRATION CALIBRATION
CENTER FREQUENCY
BESSEL
NULL
Figure 4-14. TypicalSpectrum Analyzer Display
of Bessel Null on FM Waveform
NOTE
You may need to adjust the RBW
settingon the Spectrum Analyzer in
order to see the >–50 dBc null.