CT Systems Wavetek 2500 - Page 40

3.4.3 Modulation Acceptance Bandwidth
In FM voice modulated receivers the maximum deviation accepted for a
certain reduction in SINAD sensitivity is called Modulation
Acceptance Bandwidth.
Since poor Modulation acceptance bandwidth results in degraded
sensitivity with Modulation, this test becomes important to fully
optimize receiver performance. This operating characteristic is also
essential in maintaining a communications system since when the
modulation acceptance bandwidth is poor, and exceeded, it will result
in degraded Receiver sensitivity.
Refer to Figure 3-5 for the following test procedure.
1) Perform the 12 dB SINAD test described in the previous section.
2) Increase the Model 2500 RF level 6 dB over the 12 dB SINAD
sensitivity point (a 6 dB increase is two times the uV setting on
the 2500 RF output dial).
3) Increase the 1 kHz level setting until 12 dB SINAD is read again.
4) Activate the DEV mode on the Model 2500.
5) Multiply the increase in deviation by two to obtain the
Modulation Acceptance Bandwidth as shown below:
[New deviation - Previous deviation] X 2 = Modulation Acceptance
Bandwidth
2500-MANUAL
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SEC'I'ION-3