Plastimo ECHOFISH 820 Manual De Instalación Y Funcionamiento página 23

In many situations, your fishfinder display will be affected by
undesired signals which may be caused by your boat engine,
turbulences, wiring, electrical and mechanical sources, etc.
Such undesired signals will produce unwanted marks on the
screen and may cause a misunderstanding of the underwa-
ter conditions.
In such situations ( when you see too much clutter on the
screen), increasing the Noise Filter will play an effect. The
larger the value is, the most unexpected data will be filtered.
If the Noise Filter value is too high, most of the sonar re-
turns (fishes for example) will not be displayed.
Note: in some situations while you have big trouble with noise, try to
find and fix the interference source, rather than operate your fish-
finder with a very high Noise Filter value. There are 9 levels and an
"auto" mode to set the noise filter. Auto set or levels 3-5 are suitable
for most using conditions.
To set the Noise Filter:
1- Press Menu to enter into menu setting.
2- Use the Up/Down to select Sonar option.
3- Press the right arrow to enter into Sonar setting.
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Echofish 820 – Installation & Operation manual