f. When finished setting the DAC, press Qon the
keyboard to go to the next calibration step.
When the DAC has been completely adjusted,
the program will exit to the $prompt.
g. Record step completion on the Test Record.
5. Internal FM Widemode sensitivity calibration is
accomplished by adjusting the FM Gain Control
DAC to obtain 200 MHz and 20 MHz FM devia-
tions at frequencies of 5 GHz and 15 GHz. Modu-
lating signal inputs are from the internal
Function Generator.
Perform the calibration as follows:
a. At the $prompt, type: calterm 143 and
press <ENTER>.
The screen will display the following menu:
1) Togglepolarity (this lets you go from a
positive deviation to negative deviation.)
2) Change DAC value.
3) Quit.
b. On the Spectrum Analyzer, set the Span/Div to
50 MHz per division.
c. On the computer keyboard, enter 2to begin
calibration.
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 the ‘key.
e. While observing the Spectrum Analyzer dis-
play,adjust the value of the DAC’s setting to
obtain a 100 MHz change in frequency.
f. On the keyboard, press Qto return to the
menu, then enter 1to toggle the polarity.
g. Measure the change in frequency on the Spec-
trum Analyzer.The change in frequency
should be 200 MHz. If not, enter 2and adjust
the DAC.
h. Repeat steps 5.f and 5.g as necessary to obtain
a 200 MHz frequency change. When finished
adjusting the DAC, press Qto return to the
menu.
i. On the Spectrum Analyzer,set the Span/Div to
5 MHz per division and adjust the center fre-
682XXB/683XXB MM 4-41
FM
CALIBRATION CALIBRATION