Raymarine HSB2 Plus Series Owner's Handbook Manual page 79

Chapter 3: Standard Radar Operations
and the echoes are not repetitive or consistent in position. With high winds and
extreme conditions, echoes from sea clutter may cause dense background
clutter in the shape of an almost solid disc.
Figure 3-7:
The SEA control reduces the gain level in the areas near your vessel, extending
up to 3 to 5nm depending on the wave and sea conditions. This has the effect of
reducing the sea returns to intermittent small dots, while small targets are still
visible. Gain levels further from your vessel remain unchanged.
You can use the gain and Sea control to help minimize the effects of side lobes
(see Identifying False Echo Returns on page 3-5).
Note: On short range scales, do not set the Sea control so high that all clutter
is removed, since this could stop you seeing echoes from close targets.
Tuning the Receiver
The TUNE control is used to fine tune the receiver in the scanner for maximum
A
target returns on the display. In Auto mode, the radar tunes itself automatically
U
T
on all range scales. We recommend that you leave the TUNE control in Auto
O
mode.
If you do set the TUNE control to Manual, you will need to adjust it about 10
minutes after you have turned on the radar, since the required setting changes
once the magnetron has warmed up.
You should adjust the control to obtain the maximum signal strength, as
indicated in the 8-step bar above the slider. If you cannot tune the radar
successfully, refer to Section 7.6 for information on the Tune Preset function.
Rain Clutter Control, using RAIN and FTC
The radar can see echoes from rain or snow. Returns from storm areas and rain
squalls consist of countless small echoes that continuously change size,
intensity, and position. These returns, shown in Figure 3-8sometimes appear
Sea Clutter
D3968-1
3-9