View Full Version : SONAR = Mystery in 2D

01-31-2011, 10:16 AM
Probably the most misunderstood statement I hear regarding sonar is this; "I don't think my fish finder is working right. I see lots of fish under my boat but they NEVER bite." "I troll over the same fish again and again and again, but still never get a bite."

Two points in the above statement show you this is 'user error' and not sonar error. As fishermen/women we need to always understand that what you see on the head unit is not always, nor likely UNDER your boat. Understanding that the echo returns that appear on the head unit at 30 feet ONLY means those echos are 30 feet from the transducer and within the transducer's 'coverage area'. Notice I said coverage area and didn't say 'cone angle'. The transducer's 'coverage area' will always be larger than the 'cone angle', and they share the same fulcrum point which is the center of the crystal. So while some are thinking they are trolling through the same stack of fish time and time again without a bite, they may actually be trolling about 30 feet AWAY from them which may not be close enough to elicit the reaction strike or hunger bite.

By altering our passes over the trail on the return trip, you can tell if the school of fish was to port or starboard of, or directly under your transducer.

I gotta say, when the money gets here, I'm first in line for the new Lowrance DSI units or the LSS-1 to add to my HDS. These two units remove all the guess work from 2D sonar.

Remember to think you ARE 20 feet AWAY from a large target instead of 20 feet over a large target.