by Maxwell Payne

Created on: December 27, 2010

Fish finders use sonar to visualize object in the ocean or in a lake. Sound waves emitted from the device go through the water and bounce off the ocean bottom, fish, rocks, and other underwater objects. Depending on the hardness of the object the signal sent back is of varying strengths translated into a visualization or indication of what the objects likely are. If the tuning is off the device will give incorrect depth information and either so too much "noise" of everything the sound waves hit or fail to show important objects such as schools of fish. Finding the perfect gain is crucial for getting the most out of your fish finder sonar device when out fishing. 

Switch the "gain" from automatic to manual if your fish finder has automatic settings. Locate the button or switch that changes from automatic to manual. Based on the make and model there may be an on screen menu, access the "settings" and locate the "gain" settings feature on the device.

Set the "depth range" to a distance that is three times the amount of the actual depth of water you are in. Not the same distance, not twice the distance but three times the distance. For example if you are in 200 feet of water, set the "depth range" to 600 feet. If you are in 50 feet of water set the “depth” range to 150 feet and so forth.

Slowly turn up the "gain" either using the "gain" knob or on screen adjustment controls depending on the device. You will begin to see the ocean or lake bottom reading on screen . Continue turning up the "gain" until you see a second ocean or lake bottom reading. This second reading or "echo" indicates the signal strength is so high it causes the signal to bounce off the bottom and have enough strength to hit the bottom again and come back to the device. The "echo" second bottom distance should be double the initial reading.

Set the "depth" back to the actual depth of the water you are in. For example if you tripled the depth for the tuning to 600 feet, turn it back down to 200 feet.

Repeat this process whenever you move to deeper water or shallower water to ensure the continued accuracy of the fish finder’s readings.

Reference

http://www.fishfinder-store.com/howfifiwo.html]

http://www.deep-blue-sea.org/deepbluesea-cgi-bin/pub lish/article_9.shtml]

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