Fast Acquisition - Comtech EF Data SDM-650B Installation And Operation Manual

SDM-650B Satellite Modem
The reacquisition mode is intended to reduce the time for reacquisition at lower symbol
rates. The following guidelines should be applied when using the reacquisition mode:
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Example: Demodulator operating at 64 kbit/s, an anticipated outage of 2 seconds. What
should be the minimum reacquisition setting?
Answer: = 15.2 seconds, round up for 16 seconds minimum.
The additional function for sweep reacquisition can be found in the Config menu of the
front panel. SWP_RACQ is the parameter used to set the minimum reacquisition time, as
described above.

5.4.2 Fast Acquisition

When fast acquisition is enabled, the fast acquisition algorithm is used for acquisition of
receive symbol rates of 128 kbit/s or lower. If the sweep range is set to less than 50 kHz,
acquisition will be dictated by the directed sweep specifications, and the fast acquisition
algorithm will not be used.
Rev. 6
The time specified for reacquisition must be multiples of 10% of the total
nominal sweep time. This will ensure that the modem has time to sweep across
the lock point at least once prior to termination of the reacquisition mode.
Add a little to the reacquisition time to account for the anticipated outage.
Sweep time = 8400/64 = 132 second (round fractions up). 10% of the total sweep
time is 13.2 seconds. Add 2 seconds to the minimum reacquisition time for the
anticipated outage.
Theory of Operation
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