Anritsu 682XXB - Manual (Page 150)

m.Now, adjust the center frequency control to po-
sition the high carrier at the center of the dis-
play. Note the frequency reading.
n. The difference between these two frequencies
is the actual peak-to-peak frequency deviation.
It should be 20 MHz
±0.8 MHz. If not, fine ad-
just the value of the DAC’s setting to obtain
this deviation.
o. When finished setting the DAC, press
Q
on the
keyboard to go to the next calibration step (ad-
justing the DAC to obtain 200 MHz deviation
at 15 GHz).
When the DAC has been completely adjusted,
the program will exit to the
$
prompt.
p. Record step completion on the Test Record.
4. External FM Narrow mode sensitivity calibration
is accomplished by adjusting the FM Gain Con-
trol DAC to reduce the carrier level as low as pos-
sible at frequencies of 5 GHz and 15 GHz.
Modulating signal inputs are 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 83.3 kHz
sine wave with an output level of 0.707 volts
RMS (2 volts peak to peak).
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’s setting.
Start calibration by pressing an increment key.
e. While observing the first Bessel null (Figure
4-12) on the Spectrum Analyzer display, adjust
the value of the DAC’s setting to reduce the
carrier level as low as possible.
Note
You may need to adjust the RBW setting on
the Spectrum Analyzer in order to see the
>–40 dBc null.
4-40 682XXB/683XXB MM
FM
CALIBRATION CALIBRATION
CENTER FREQUENCY
BESSEL
NULL
Figure 4-12. Typical Spectrum Analyzer Display
of Bessel Null on FM Waveform