Furuno FR-8251, FR-8111 Ship’s Graphic, Interference Rejector, Echo Trails, Manual speed input

Manual speed input

1)Press the MENU key.

2)Select the INITIAL menu and press the EN- TER/SELECT key.

3)Select SPD MODE and press the ENTER/ SELECT key.

4)Select MANU.

5)Press the ENTER/SELECT key.

6)Enter speed and press the ENTER/SELECT key.

7)Press the MENU key.

1.24 Ship’s Graphic

A graphic ( ) which depicts own ship can be displayed. This function is not available on the N-type radar.

1)Press the MENU key.

2)Select the INITIAL menu.

3)Press the ENTER/SELECT key.

4)Select SHP GRPH and press the ENTER/SE- LECT key.

5)Select ON (or OFF).

6)Press the ENTER/SELECT key.

7)Press the MENU key.

1.25 Interference Rejector

Mutual radar interference may occur in the vi- cinity 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 ir- regular patterns or in the form of usually curved spoke-like dotted lines extending from the cen- ter to the edge of the picture. This type of inter- ference can be reduced by activating the interference rejector circuit.

The interference rejector circuit is a kind of sig- nal correlation circuit. It compares the received signals over successive transmissions and sup- presses randomly occurring signals. There are three levels of interference rejection depending

on the number of transmissions that are corre- lated. These are indicated by the legends IR1, IR2 and IR3 at the bottom right-hand position of the screen.

To turn on or off the interference rejector circuit;

1)Press the MENU key.

2)Select ECHO SIG and press the ENTER/SE- LECT key.

3)Select INTRF and press the ENTER/SELECT key.

4)Select level of suppression desired (higher the number the greater the suppression) and press the ENTER/SELECT key.

5)Press the MENU key.

Figure 1-20 Radar interference

1.26 Echo Trails

Echo trails are simulated afterglow of target ech- oes that represent their movements relative to own ship or true movements with respect to land, in a single tone or gradual shading depending on the setting on the TRAIL menu.

True or relative trails

You may display echo trails in true or relative motion. Relative trails show relative movements between targets and own ship. In the true mo- tion, the moving targets have trails according to their speeds, but stationary targets stay still.

True motion trails require a gyrocompass signal and own ship speed input to cancel out own ship's movement and present true target movements in accordance with their over-the-ground speeds and courses (not heading). Refer to the automatic and manual speed input procedures for entering own ship's speed information.

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