How to adjust A/C RAIN and FTC (suppressing rain clutter)
The vertical beamwidth of the scanner is de- signed to see surface targets even when the ship is rolling. However, by this design the unit will also detect rain clutter (rain, snow, hail, etc.) in the same manner as normal tar- gets. Figure
2.9 Tuning the Receiver
The receiver can be tuned automatically or manually. For automatic tuning the receiver is tuned each time you switch from stand- by to transmit. For manual tuning, the re- ceiver is properly tuned when the longest tuning indicator appears. (However, the length of the indicator changes with the num- ber of radar echoes, range and other factors.)
Adjusting A/C RAIN
When rain clutter masks echoes over a wide range, raise the A/C RAIN slightly to dis- tinguish targets from the clutter.
1.5NM
0.5
Tuning
indicator 
AUTO
Appearance of | A/C RAIN adjusted; |
rain clutter | rain clutter suppressed. |
Figure 2-6 Effect of A/C RAIN
Adjusting FTC
To suppress rain clutter from heavy storms or scattered rain clutter, adjust the FTC. The FTC circuit splits up these unwanted ech- oes into a speckled pattern, making recog- nition of solid targets easier. FTC and selected level appear at the top
Note: In addition to reducing clutter, the FTC can be used in fine weather to clarify the pic- ture when navigating in confined waters. How- ever, with the circuit activated the receiver is less sensitive. Therefore, turn off the circuit when its function is not required.
Figure 2-7 Tuning indicator
Manual tuning
The default tuning method is automatic. To switch to manual tuning;
1)Press the [MENU] key to open the menu.
2)Press the cursor pad to select Tuning.
3)Press the cursor pad to select MANUAL.
4)Press the [ENT] key followed by the [MENU] key.
How to tune manually
While pressing and holding down the [HM OFF] key, press the 9 o'clock or 3o'clock position on the cursor pad to tune. Tune to show the longest tuning indicator.
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