T R I P L E T H R E AT

If you’re seeking the latest sonar for depths exceeding 150 feet, Simrad’s S5100 High-Performance Chirp Sonar Module offers three independent sonar channels in one black-box housing. Owners of compatible Simrad equipment — including NSS evo2 and NSS evo3 MFDs, NSO evo2 glass-bridge systems and S2000series fish finders — can monitor sonar imagery from multiple depths simultaneously. The S5100 ($1,999) is compatible with 600 W to 3 kW transducers and can be configured using three single-channel transducers, or one single-channel transducer and one dual-channel transducer. Imagery is sent via Ethernet to three independent MFDs/screens, or to one MFD that’s operating in split-screen mode plus a second single-screen display. Users can select chirp frequencies from 28 to 250 kHz, and they can adjust the power output depending on their intended targets. display (MFD). Higher-frequency sonar waves provide higher-resolution imagery, while lower-frequency waves provide better range (think AM and FM radio, where FM signals provide superior sound quality but can’t propagate as far as their AM brethren).

In all cases, the quality of returned sonar information depends greatly on the power and frequency of the transmitted pulse. Recent years have seen the rise of chirp sonars that simultaneously broadcast transmissions over a sweep of predetermined frequencies at a power output ranging between 300 W and 3 kW, delivering better image resolution and target separation. These transmissions are broadcast as siren-like shrills that are inaudible to human ears but that let the sounder “peer” through targets, such as tightly packed bait schools, by comparing the original transmission (and its time stamp) with the returned sonar energy.

Realizing that chirp sonars’ significantly higher-frequency signals yield significantly better short-range sonar imagery, Humminbird’s engineers created Mega Imaging, which comes bundled on select Helix and Solix MFDs. Customers can choose between MFDs that offer just Mega Down Imaging (DI) or ones that offer both Down Imaging and Side Imaging (SI). “With Mega Imaging, we went from ‘it looks like a roadbed’ to ‘it looks like a roadbed with a cinder block or a two-by-four lying there,’” says Humminbird’s brand manager, Ray Schaffart. He likened the jump from traditional sonar to Mega Imaging to the sea-change leap from console TVs to high-definition flatscreen TVs. “In 30 feet of water, you can see the sand ripples,” he says.

By harnessing frequencies between 1.125 MHz and 1.3 MHz, Mega Imaging delivers eye-popping imagery 125 feet below the transducer and 125 feet to each side. The system requires at least one special, multi-element transducer that