A fish finder is a sonar: a transducer under the boat sends a pulse of sound into the water, times the echo, and the display draws what came back. Every feature on the box, CHIRP, ClearVü, MEGA Imaging, LiveScope, is a variation on that one idea, and every buying decision comes down to three questions: what frequency the unit uses, whether it draws pictures or arches, and whether it can show fish moving in front of the boat. Get those three questions right and the model ladders of Garmin, Humminbird and Lowrance turn from a price list into a choice.
A 200 kHz beam sees a cone about a third as wide as the water is deep; drop to 83 kHz and the cone is about as wide as it is deep. That one fact decides what your screen is showing you.
Start here
- Fishing gear — the section hub, where each category’s key number is explained.
- Fishing reels and fishing rods — the tackle the electronics are meant to put in the right place.
- Bass fishing — the species that drove the live-sonar boom and the tournament rules that followed.
Frequency and cone angle
Sound leaves the transducer in a cone. The lower the frequency, the wider the cone and the deeper it reaches, at the cost of detail; the higher the frequency, the narrower and sharper the picture. Lowrance’s figures for its standard 83/200 kHz transducers are 20 degrees at 200 kHz and 35 to 50 degrees at 83 kHz, and the working rule that follows is simple: at 83 kHz you see a patch of bottom about as wide as the water is deep, at 200 kHz about a third as wide. CHIRP sonar sweeps a band of frequencies in each pulse instead of one, which separates targets that a single frequency would blur into one arch; Garmin’s CHIRP bands run 425–485 kHz and 790–850 kHz on its imaging transducers, Raymarine’s 320–380 kHz.
| Sonar type | Frequency | What it draws | Reach |
|---|---|---|---|
| Traditional 2D | 50, 83 or 200 kHz | Fish as arches, bottom as a band | Deepest; 50 kHz for offshore |
| CHIRP 2D | a swept band | Cleaner arches, better target separation | As 2D |
| Down imaging (ClearVü, DownScan, Down Imaging) | 455 or 800 kHz | A picture-like slice under the boat, about 60 degrees wide | About 600 ft (183 m); Garmin CHIRP 750 ft (229 m) |
| Side imaging (SideVü, SideScan, Side Imaging) | 455, 800 kHz or Humminbird MEGA at 1.2 MHz | Structure and fish out to each side | Up to about 600 ft (183 m) per side on the best units |
| Forward-facing live sonar (LiveScope, ActiveTarget, MEGA Live) | about 1 MHz | Fish and lure moving in real time ahead of the boat | LiveScope Plus 20 × 135 degree view; MEGA Live 20 × 120 |
Humminbird’s MEGA Imaging at 1.2 MHz is the highest frequency in any recreational fish finder, which is why its side-imaging pictures are the sharpest and its reach the shortest.
Reading the screen
On 2D sonar a fish is an arch because it moves through the cone: it enters at the edge, is closest in the middle and leaves at the far edge, and the echo time draws a curve. A full arch means the fish crossed the whole cone; bigger fish draw longer, thicker arches. On down imaging the same fish is a dot, because the beam is too thin to draw a curve. A hard bottom returns a thick, strong band, a soft mud bottom a thin, faint one; colour palettes show hard as yellow or red and soft as blue. Baitfish appear as a cloud of dots, weed as a fuzzy carpet above the bottom, and the thermocline in summer as a faint horizontal band where the water temperature drops.
Live sonar and the tournament rules
Forward-facing sonar arrived with Garmin’s Panoptix in 2015 and LiveScope in 2018; Lowrance’s ActiveTarget and Humminbird’s MEGA Live followed in 2021, and Humminbird’s MEGA Live 2 with the XPLORE heads in December 2024. A transducer alone costs about $1,500 to $1,700 before the display. Outdoor Life’s comparison calls MEGA Live and LiveScope “close to a tie, with Garmin getting a slight edge”. The technology changed competitive bass fishing enough that the leagues stepped in: B.A.S.S. limits Elite Series boats to one live-sonar transducer and 55 inches of total screen, and from 2026 allows the technology in at most five of nine regular-season events, chosen by coin flip; Major League Fishing limits the Bass Pro Tour to two transducers and one of three periods a day; the NPFL banned it outright from 2025.
The three brand ladders
| Brand | Entry | Mid | Premium | Live sonar |
|---|---|---|---|---|
| Garmin | Striker Vivid 4–9 in (no charts) | ECHOMAP UHD2 5–9 in, Navionics+ maps | ECHOMAP Ultra 2 10–16 in; GPSMAP 7–27 in | ECHOMAP and GPSMAP only, not Striker |
| Humminbird | PiranhaMAX; HELIX 5–12 G4/G4N | SOLIX; XPLORE 9–12 (2024) | APEX 13–19 in, full HD | MEGA Live 2 on APEX, SOLIX G3 and XPLORE only |
| Lowrance | Eagle 4–9 in; HOOK Reveal | Elite FS 7–12 in | HDS PRO 9–16 in | ActiveTarget 2 on Elite FS and HDS PRO |
The trap in every ladder is compatibility: a Garmin Striker cannot run LiveScope, a Humminbird HELIX cannot run MEGA Live 2 or network with an XPLORE. Buy the display for the sonar you want in two years, not the one you want today.
Where to go next
The pages under this hub cover how to read a fish finder, forward-facing sonar in depth, the Garmin, Humminbird and Lowrance line-ups one by one, and the portable and kayak units, where a castable puck or a 5-inch screen on a 12 V 10 Ah lithium battery is the right answer. The fishing gear hub places electronics next to the rod, reel, line and hook decisions, and the catfish and bass hubs say what the sonar is looking for.