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2. FINE TUNING THE SONAR PICTURE
2-5
2.5 Rejecting 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.
2.5.1 Identifying 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.
2.5.2 Rejecting 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.
2.5.3 Rejecting 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.