FM Input
Sensitivity
Procedure
The following procedure lets you perform measure-
ments in Unlocked Wide, Unlocked Narrow, and
Locked FM modes and determine FM accuracy.
Unlocked Wide FM Mode
1. Set up the 691XXB as follows:
a. Reset the instrument by pressing
SYSTEM
,
then
Reset
. Upon reset, the CW Menu is dis-
played.
b. Press
Edit F1
to open the current frequency
parameter for editing.
c. Set F1 to 5.0 GHz.
2. Set up the Function Generator for a 0.4 Hz
square wave with an output level of
±
1 volt
(2 volts peak to peak).
3. Set up the Spectrum Analyzer as follows:
a. CF: 5 GHz
b. Span/Div: 50 MHz (500 MHz across the dis-
play)
4. On the 691XXB, make the following settings:
a. Press
MODULATION
, then
FM
. At the result-
ing External FM Status menu, press
More
to
go to the additional External FM Status menu.
b. At this menu, press
Unlocked Wide
, then
press
Previous Menu
to return to the main Ex-
ternal FM Status menu.
c. At the main External FM Status menu, press
Edit Sens
and set the sensitivity to
100 MHz/V.
d. Press
On / Off
to turn FM on.
5. On the Spectrum Analyzer, change the Span/Div
setting to 5 MHz to use the analyzer as a fre-
quency counter.
a. Adjust the center frequency control to position
the low carrier at the center of the display. Re-
cord the frequency reading on the Test Record.
b. Adjust the center frequency control to positon
the high carrier at the center of the display.
Record the frequency reading on the Test Re-
cord.
3-32
690XXB/691XXB MM
PERFORMANCE
FREQUENCY
VERIFICATION
MODULATION TESTS
Summary of Contents for 680 C Series
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