Cobra Electronics MF 2500 manual Frequently Asked Questions

Frequently Asked Questions

decreasing the STC value to SHORT in shallow waters or to switch it to VERY SHORT or OFF.

4.8.2Auto range fails, and the digital depth readout displays a very shallow reading. What should I do?

This usually happens if the STC is off or is set to a low value causing disturbs from surface clutter to be stronger than bottom echoes. Try increasing the STC value. As general rule STC has to be set as in shallow waters and LONG in depth waters.

4.8.3Auto-range fails in very deep waters displaying a digital very shallow depth readout. What should I do?

The Fish Finder capability to detect the bottom decreases as the bottom depth increase. If the bottom composition is soft as mud, if the sea conditions are bad, if there are thermoclines or the water is full of materials in suspension it can further decrease thus causing the digital depth readout to fail. When this happens the auto-range algorithm also fails. To recover from this situation it is necessary to switch to manual range mode and to set the manual depth mode. When manual depth mode is selected the algorithm that calculates the digital depth readout searches for the bottom within the range manually selected by the user. At this point it is necessary to increase manually the range until the bottom becomes graphically visible. If the echoes from the bottom are strong enought, the Fish Finder shall look to the bottom giving a correct depth reading and shall be possible to return in auto range mode. Please note that if one or more of the conditions that reduce the echoes from the bottom listed above is true the bottom may be not visible at all, in this situation a strong thermocline or surface clutter may be interpreted by the Fish Finder as the bottom.

4.9At a very shallow range upper half of the screen appears almost completely filled by the surface clutter. How can I eliminate it?

This is normal in shallow waters. To clean up the surface clutter without degrading the digital depth readout algorithm functionality it is possible to set the STC value to custom setting the STC lenght to the same size of the surface clutter, and increasing the STC strenght until the image on the screen cleans up. Please note that in very shallow waters it is usually better to switch to manual gain mode to reduce gain fluctuation due to rapidly changing bottom conditions.

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