Furuno FR-8111, FR-8251 Echo Stretch, Noise Rejection, Selecting Pulselength, 27 Echo stretch

1.32 Echo Stretch

On long ranges target echoes tend to shrink in the bearing direction, making them difficult to see. On short and medium ranges such as 1.5, 3 and 6 nm range scales, the same sized targets get smaller on screen as they approach own ship. These are due to the inherent property of the ra- diation pattern produced by the antenna. To en- hance target video, use the echo stretch feature.

Enlarged in range

direction by ES 2

Enlarged by ES 1

Note 3: Suppress sea clutter and noise before activating echo stretch, since the echo stretch cir- cuit stretches not only target echoes but also sea clutter and noise.

Note 4: Echo stretch 2 is not available with the short pulse.

1.33 Noise Rejection

White noise can be suppressed by turning on N REJ on the ECHO SIG menu.

+

If a target becomes

smaller as it approaches

own ship, use ES 1.

ECHO STRETCH 1 For stretching echoes near own ship

+

If a distant target is hard to see, use ES 2.

ECHO STRETCH 2 Forstretching echoes near perimeter of CRT

1)Press the MENU key.

2)Select the ECHO SIG menu.

3)Press the ENTER/SELECT key.

4)Select N REJ and press the ENTER/SELECT key.

5)Select ON.

6)Press the ENTER/SELECT key.

7)Press the MENU key.

Figure 1-27 Echo stretch

1)Press the MENU key.

2)Select the ECHO SIG menu and press the ENTER/SELECT key.

3)Select STRETCH and press the ENTER/SE- LECT key.

4)Select 1 2, or OFF.

5)Press the ENTER/SELECT key followed by the MENU key.

Note 1: Echo stretch magnifies not only small target pips but also returns from sea surface, rain and radar interference. For this reason, make sure that these types of interference have been suffi- ciently suppressed before activating the echo stretch feature.

Note 2: If the 1.5 nm range is preset for pulselength SP (0.08 μs) or M2 (0.3 μs), and the 3 nm scale for M1 (0.3 μs), the echo stretch fea- ture is not available on these range scales.

1.34 Selecting Pulselength

Pulselength can be selected on the ranges between

0.75and 24 nautical miles, on the menu. Pulselengths available are a short pulse, two me- dium pulses, and a long pulse.

Presetting pulselength

Two sets of pulselengths can be preset on the ECHO SIG menu: P/L SET 1 and P/L SET 2.

1)Press the MENU key.

2)Select the ECHO SIG menu.

3)Press the ENTER/SELECT key.

4)Select P/L SET 1 (or P/L SET 2) and press the ENTER/SELECT key.

5)Select pulselength and press the ENTER/SE- LECT key.

6)Select P/L SET 2 (or P/L SET 1) and press the ENTER/SELECT key.

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