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3
rd
Generation Rack-
Mount RDMS™
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Quasonix, Inc.
Figure 42: Derandomizer Selections, LDPC or Reed-
Solomon Not Enabled
Figure 43: Derandomizer Selections, LDPC or
Reed-Solomon Enabled
4.4.2.12 Modulation Scaling (PCM/FM Mode Only)
Modulation Scaling is a method used to retain the maximum trellis coding gain of a non-ideal FM signal. There are
four possible settings: Tracking, Hold, Off, or Acquire.
The RDMS™ automatically adjusts demodulator bandwidth based on the selected/estimated modulation index.
However, IF filter bandwidth is not automatically adjusted, even when set to automatic. It is recommended that the
user manually scale the IF filter bandwidth proportional to the modulation index for modulation indexes greater than
1.0.
4.4.2.12.1 Modulation Scaling
–
Tracking
When the RDMS™ is powered on, the default setting is Acquire, unless the unit was powered off from a preset
condition. If the unit was powered off from an unmodified preset setting, then the default condition of Modulation
Scaling is as defined in the preset. When Tracking is set, the modulation scale index is actively being tracked.
Note:
The active setting is not saved when the rack is powered off, unless the Mod Persist option was set to On.
Frequency, mode, and bit rate changes, or any changes to a preset, cause the Modulation Scaling setting to revert
back to Tracking. This is because the optimal signal monitoring is no longer valid.
Note:
Whenever the Diversity Combiner is On, any changes made to the Frequency option (even with Frequency
Diversity On enabled) causes Modulation Scaling for both channels to be set to Tracking.