It just doned on me . Last year I bought a new depthfinder. Upgraded to a Lawrance. Don’t want to say what I had but it could fly. Anyway I can’t find out what the pattern is when I’m in 15 ft. of water. Not that it matters a whole lot I just want to know. It has a 20 degrees ducer. Would it be the same ? About 5 ft. in 15ft. of water ? Jim
Jim,
The following is from Ken Schultz from Cabelas website… The breadth that sonar can view beneath a boat is greatly affected by the diameter of the cone, which in turn is a function of the viewing angles. Cone angles for sportfishing are characterized as narrow (roughly 8 to 10 degrees), medium (roughly 16 to 20 degrees), and wide (roughly 45 to 60 degrees, or more). Many people greatly overestimate the amount of area that they can view beneath their boat.
A general guideline for determining viewing area is to divide the depth by 6 for narrow cone angle sonar, and by 3 for medium cone angle sonar. For example, if the bottom depth where you’re fishing is 18 feet, a transducer with a 9-degree cone angle views an area that is roughly 3 feet in diameter, while a transducer with an 18-degree cone angle views an area that is roughly 6 feet in diameter.
With wide cone angle sonar, the viewing area at the bottom is nearly the same as the depth. It’s a 1:1 ratio, for example, with a 60-degree cone, so that in 18 feet of water, you view an area that is 18 feet in diameter. The bottom diameter is a little less, of course, when using a 45- or 50-degree cone.
Wade– Then it is about the same as the one I had last year. It was 5 ft’ at 15′ or there abouts. In 18′ it would be 6′. Just courious. These are some things I just like to know. Did not know how to figure it when you get over 15′ . Now I do. Thank You Jim
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