Speed Log - Raytheon NSC 18 User Manual

The effect of the Sea control is at its greatest at short range. Its effect reduces
progressively as the range increases. At a range determined by the height of the
radar antenna above the water (and other factors), the effect of the SEA
control ceases altogether. This is typically about 8−10nm.
The ideal sea control setting will reduce sea returns to a light speckle.
Scan−to−scan integration will keep the sea returns at a low brightness level,
while targets in the sea clutter will be shown at full brightness.
The sea clutter control should be adjusted in small increments, with pauses to
observe 3 scans for the results.
In heavy sea clutter, some clutter peaks may come through at brighter levels,
especially rollers, so an average setting should be chosen. It is important to note
that if the Sea Clutter control is adjusted to completely remove all clutter, then
some targets may not be detected.
The NSC uses gyro and speed information as part of the clutter removal
process. It is therefore highly recommended that you use gyro stabilization
and ensure that the manual speed or speed log input is accurate.
In heavy wind driven seas where more sea clutter appears on the windward side
of the ship, a slight amount of FTC can balance the clutter (see chapter 2.3.1.6)
Then adjust the SEA control to reduce sea clutter. If too much SEA is applied
during periods of light clutter, then a band of noise could appear on the edges of
the sea clutter.
3748DOC020102
Operator Manual
NOTE
2−28
Edition: 14.JAN.2005