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5. On the 691XXB, use the cursor control key to
place the cursor under the last 0 in the sensitivity
setting (0.240 MHz/V). While observing the first
Bessel null (Figure 3-9), increase/decrease the
sensitivity setting with the cursor control key to
reduce the carrier as low as possible.
6. Record the FM sensitivity setting, displayed on
the 691XXB, on the Test Record.
7. Compute the FM accuracy with the following for-
mula:
Accuracy in
FM Sensitivity in kHz
(
%)
(
)
=
æ
è
ç
ö
ø
÷ ´
240
100
8. The calculated result should be between 93.7%
and 106.3%. Record this result on the Test Re-
cord.
690XXB/691XXB MM
3-35/3-36
PERFORMANCE
FREQUENCY
VERIFICATION
MODULATION TESTS
Summary of Contents for 680 C Series
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