Furuno 841 MARK-2 manual Suppressing Radar Interference, Canceling the guard zone

pressing the [GUARD] key. When this is done, G (ACKN) replaces G (IN) (or G (OUT)).

Press the [GUARD] key again to reactivate the alarm. G (IN) (or G (OUT)) replaces G (ACKN).

Canceling the guard zone

Press and hold down the [GUARD] key until the guard zone disappears.

Notes on the guard alarm

•When the radar range is less than one half of the guard zone range, the guard zone disappears from the display and UP RANGE appears. If this happens, raise the range to redisplay the guard zone.

•A target echo does not always mean a landmass, reef, ships or surface objects but can imply returns from sea surface or precipitation. As the level of these returns

Asterisk blinking
Guard zone	* G (IN)
to set

	Drag cursor
	here.
(1) Mentally create	(2) Drag cursor to
the guard zone to set.	top left corner of
	zone and press
	[GUARD].

G (IN) G (IN)

Guard zone

	Drag cursor
	here.
(4) Guard zone	(3) Drag cursor to
completed.	bottom right corner
	of zone and press
	[GUARD].

Figure 2-14 How to set a guard zone

varies with environment, the operator should properly adjust the STC, gain (sen- sitivity), A/C RAIN and FTC to be sure the alarm system does not overlook tar- get echoes.

2.17Suppressing Radar Interference

Radar interference may occur when near an- other shipborne radar operating in the same frequency band as your radar. Its on-screen appearance is many bright dots either scat- tered at random or in the form of dotted lines extending from the center to the edge of the display. Figure 2-15 illustrates interference in the form of curved spokes. Interference effects are distinguishable from normal ech- oes because they do not appear in the same place on successive rotations of the scan- ner.

Figure 2-15 Radar interference

Four levels of interference are available, in- cluding off: IR1, IR2, IR3 and OFF. IR3 provides the highest level of rejection.

Procedure

1)Press the [MENU] key.

2)Select P/L & Int/Noise Rej & ES and press the [ENT] key.

3)Select INT REJECT.

4)Select level desired; 2 provides the great- est degree of interference rejection

4) Press [ENT] and [MENU].

IR and level selected appear at the top right

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