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Narrow FM Mode
1. Set up the 682XXB/683XXB 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 Spectrum Analyzer as follows:
a. CF: 5.0 GHz
b. Span/Div: 100 kHz (1 MHz across the display)
3. On the 682XXB/683XXB, make the following set
-
tings:
a.
Press MODULATION , then FM . At the re-
sulting FM Status menu, press More to go to
the additional FM Status menu.
b. At the additional FM Status menu, press
Narrow , then press Previous Menu to return
to the main FM Status menu.
c.
At the FM Status menu, press Edit Dev. and
set the deviation to 2.40 rad.
d.
Press Edit Rate and set the rate to 99.8 kHz.
e.
Press On/Off to turn FM on.
4. On the 682XXB/683XXB, use the cursor control
key to place the cursor under the last 0 in the de
-
viation setting (2.40
rad). While observing the
first Bessel null (Figure 3-15), increase/decrease
the FM deviation with the cursor control key to
reduce the carrier as low as possible.
5. Record the FM deviation, displayed on the
682XXB/683XXB, on the Test Record.
6. Compute the FM accuracy with the following for
-
mula:
Accuracy in
M Deviation inrad
(%)
()
.
=
æ
è
ç
ö
ø
÷
´
F
240
100
7. The calculated result should be between 93.7%
and 106.3%. Record this result on the Test Re
-
cord.
3-50 682XXB/683XXB MM
PERFORMANCE PHASE
VERIFICATION MODULATION TESTS
NOTE
You may need to adjust the RBW
setting on the Spectrum Analyzer in
order to see the >–48 dBc null.