Sonar Technology Traditional Sonar

Traditional sonar, also called 2D sonar or broadband sonar, is the original fish finder technology. It sends a single-frequency ping at a fixed frequency — typically 50 kHz, 83 kHz, or 200 kHz — and displays the returns as a scrolling column on your screen. As your boat moves, new columns stack beside the old ones, creating a continuous picture of the bottom, structure, and fish beneath you.

The display scrolls from right to left, with the newest data on the right edge. Fish appear as arches because the sonar cone first detects them at the cone's outer edge (farther away), then at the center (closest point), then at the trailing edge (farther again). This distance change creates the characteristic arch shape. Stronger returns display as thicker, brighter marks.

Traditional sonar remains useful despite the rise of CHIRP and imaging technologies. The wide cone angle covers a broader area directly below the boat, making it effective for locating schools of baitfish or suspended fish. Many experienced anglers prefer the simplicity of a well-tuned 2D display for quickly scanning water while trolling or drifting.

Most modern fish finders still include a traditional 2D sonar view alongside CHIRP and imaging modes. Running a traditional view on one panel while using down imaging on another gives you complementary perspectives — the traditional view shows the water column effectively, while imaging provides photographic detail of bottom structure.