Furuno FR-1710 manual Suppressing Precipitation Clutter, Interference Rejector

1.16Suppressing Precipitation 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, or hail) in the same manner as normal tar- gets. Figure 1-12 shows the appearance of rain clutter on the display.

The A/C RAIN control adjusts the receiver sensitivity as the A/C SEA control does but rather in a longer time period (longer range). Clockwise rotation of this control increases the anti-clutter effect.

A/C RAIN control	A/C RAIN control
OFF	adjusted

Figure 1-12 Effect of A/C RAIN control

1.17 Interference Rejector

Mutual radar interference may occur in the vicinity of another shipborne radar operating in the same frequency band (9 GHz). It is seen on the screen as a number of bright spikes either in irregular patterns or in the form of usually curved spoke-like dotted lines extending from the center to the edge of the picture. This type of interference can be re- duced by activating the interference rejector circuit.

The interference rejector is a kind of signal correlation circuit. It compares the received signals over successive transmissions and suppresses randomly occurring signals.

There are three levels of interference rejec- tion depending on the number of transmis- sions that are correlated. These are indicated by the legends IR1, IR2 and IR3 at the lower- left position of the screen.

Figure 1-13 Interference

To activate the interference rejector;

1.Press the [MENU] key.

2.Press the [5] key twice to select ECHO SIG.

	ECHO SIG
1.	TGT COLOR	YEL			GRN		COLOR
2.	ECHO AVG	OFF			0.5	1	2 3
3.	INT REJ	OFF			1	2	3
4.	N REJ	OFF			ON
5.	ENHANCE	OFF			ON
6.	2ND ECHO	OFF			ON
7.	CONTRAST	1	2		3
8.	CLTR SWEEP	OFF		ON(LINK) ON(FIX)
9.	SWEEP LVL	1	2		3
0. CNTR ENHANCE		OFF			ON

Figure 1-14 ECHO SIG menu

3.Press the [3] key to select interference rejection level (OFF, 1, 2, or 3) from the INT REJ field.

4.Press the [ENTER/SELECT] key.

5.Press the [MENU] key.

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