Frequencies, CHIRP, and Cone Angles

Frequency is simply the pitch of the ping, measured in kilohertz (kHz). Your unit likely offers at least two: something high (usually 200 kHz) and something lower (83 kHz on most units, 50 kHz on deep-water units). The tradeoff is baked into physics and applies to every sonar ever made: HIGH frequency gives a narrower beam, finer detail, and crisper target separation, but the energy fades faster with depth. LOW frequency spreads wider and punches deeper, but everything it draws is fuzzier.

Now attach the cone angles, because frequency and cone width travel together. At 200 kHz you get roughly a 20° cone — the detail beam. At 83 kHz you get roughly 60° — the search beam. In 20 feet of water that's the difference between watching a 7-foot circle of bottom and a 23-foot circle. The wide beam sees about three times the width of water — nine times the area — but smears everything in it together and even fudges the depth reading on slopes, since it's averaging a much bigger patch of bottom.

Here's the honest answer: at kayak depths — almost always under 60 feet, usually under 30 — 200 kHz has all the depth reach you need, and its detail advantage wins nearly every time. Make high frequency your default and treat the wide beam as a tool you deliberately pick up in two situations.

Situation one: hunting suspended fish in open water. When crappie or stripers could be anywhere in the water column and you're covering water to find them, the 60° cone triples your search width — you don't need crisp, you need CONTACT. Mark them wide, then switch narrow to work them. Situation two: drifting deeper water where the skinny cone covers so little bottom that you're essentially fishing blind between pings. Wide beam turns a drinking straw into a funnel.

Many units let you run both at once in a split screen. That's not a gimmick — wide beam to detect, narrow beam to inspect is a legitimate professional workflow, and it costs you nothing but a button press.

Traditional sonar pings one pure tone — say, exactly 200 kHz — and listens. CHIRP (Compressed High-Intensity Radiated Pulse) sends a longer ping that SWEEPS across a whole band of frequencies, like sliding a finger up the piano instead of striking one key. A 'high CHIRP' ping might sweep 150 to 240 kHz in a single pulse.

Why bother? Because different frequencies bounce slightly differently off different objects, and the unit can match returning echoes to the exact moment in the sweep that produced them. The practical payoff is TARGET SEPARATION — the ability to draw two things that are close together as two things. A fish hovering two feet over bottom stops melting into the bottom line. A bait school stops being one smear and becomes texture. Crucially, fish sitting INSIDE a bait ball start showing as distinct thicker marks in the cloud — that's a fishable piece of information.

Almost every unit sold in the last several years has CHIRP, often labeled as bands rather than numbers: 'High CHIRP' (roughly 150–240 kHz) is your kayak default; 'Medium CHIRP' (roughly 80–160 kHz) is the wide search beam's upgrade. If your unit has CHIRP, turn it on and leave it on. There is no realistic downside at kayak depths.

Down imaging and side imaging — coming in lessons 6 and 7 — run at much higher frequencies still: 455 kHz, 800 kHz, and the megahertz-class beams brands call MEGA or Ultra High-Definition (around 1,200 kHz). Same physics, pushed to the extreme: at those frequencies the picture becomes almost photographic, and the working range shrinks to about 100–150 feet, which on a kayak is plenty.

One mental model to carry forward: EVERY sonar view you'll ever use sits somewhere on the same detail-versus-reach line. 50 kHz is the deep-sea end. 200 kHz CHIRP is the all-round middle. MEGA imaging is the microscope end. Once you see the whole product wall as one dial, the acronyms stop being intimidating.