Furuno CSH-5L/CSH-8L manual Rejecting Sonar Interference and Noise, Identifying noise source

2. FINE TUNING THE SONAR PICTURE

2.5Rejecting Sonar Interference and Noise

While observing the sonar picture, you may encounter occasional or intermittent noise and interference. These are mostly caused by on-board electronic equipment, engine or propeller noise, or electrical noise from other sonars being operated nearby.

2.5.1Identifying noise source

To eliminate noise effectively, you should first identify the noise source.

•Turn off “TRANSMISSION” in the SONAR menu to stop transmission and operate all on board equipment one by one while observing the picture.

•Run the boat at various speeds to check if the noise is speed dependent.

If neither of the above two steps affects on the picture, adjust the INT REJECT (Interference Rejector), NOISE LIMITER or TX CYCLE on the SONAR menu as appropriate.

2.5.2Rejecting noise with the interference rejector

This control is similar to the interference rejector on echo sounders and radars. It is effective for rejecting random noise and sea surface reflections in rough sea conditions. Set the interference rejector so that noise is just eliminated. Do not use an unnecessarily high setting since small wanted echoes may also be rejected.

1.Press the MENU key.

2.Use the [RANGE] control to choose [MENU MODE] at the top of the screen.

3.Use the [GAIN] control to choose SONAR to display the SONAR menu.

4.Use the [RANGE] control to choose INT REJECT.

5.Use the [GAIN] control to set interference rejection level, from 0 (OFF) to 3 (highest degree of suppression).

6.Press the [MENU] key to close the menu.

2.5.3Rejecting noise with the noise limiter

Weak, unwanted reflections, colored light blue or green, are displayed when water is contaminated or plankton layers exist or due to ship’s noise.

1.Press the MENU key. The last-used menu appears.

2.Use the [RANGE] control to choose [MENU MODE] at the top of the screen.

3.Use the [GAIN] control to choose SONAR to display the SONAR menu.

4.Use the [RANGE] control to choose NOISE LIMITER.

5.Use the [GAIN] control to set noise limiter level. The setting range is 0-10 and the higher the figure the greater the degree of suppression.

6.Press the [MENU] key to close the menu.

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