Furuno FR-1710 manual Pulselength, Echo Stretch, Echo stretch

1.13 Pulselength, Echo Stretch

The ECHO control selects pulselength, and echo stretch when it is not turned on with a user key ([F1], [F2], [F3]). The pulselength in use is displayed at the upper-left position of the screen using the abbreviations (suffixed with “P”) shown in the table on the next page. Echo stretch level (ES1, ES2) in use appears at the bottom left position, using the indica- tion ES1 or ES2.

Appropriate pulselengths are preset to indi- vidual range scales and function keys. There- fore, you are not usually required to select them. If you are not satisfied with the current pulselength settings, however, it is possible to change them by the ECHO control. The ECHO control settings which can select the echo stretch are shown in the table below. The legend and pulselengths are shown in below.

FR-1710/1725	FR-1760DS
S1P: 0.07 µs	SP: 0.08 µs
S2P: 0.15 µs	M1P: 0.3 µs
M1P: 0.3 µs	M2P: 0.6 µs
M2P: 0.5 µs	LP: 1.2 µs
M3P: 0.7 µs
LP: 1.2 µs

On long ranges target echoes tend to shrink in the bearing direction, making them diffi- cult to see. On short and medium ranges such as 1.5, 3 and 6 nm scales, the same size targets get smaller on screen as they ap- proach the own ship. These are due to the inherent property of the radiation pattern of the antenna. To enhance target video, use the echo stretch function. There are two types: echo stretch 1 (ES1) to enlarge in bear- ing direction for long range detection, and echo stretch 2 (ES2) to enlarge in range di- rection.

Note: The echo stretch magnifies not only small target pips but also returns (clutter) from sea surface, rain and radar interference. For this reason make sure these types of inter- ference have been sufficiently suppressed before activating this function.

Enlarged in bearing (circumferential) direction with ES1

+

If a distant target is hard to see, use ES 1.

Enlarged with ES2

+

If a target becomes smaller as it approaches own ship, use ES 2.

Figure 1-10 Echo stretch

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