New Transducers

Advanced sonar technology demands rethinking transducer requirements.

May 28, 2013
All Arounder: With the transom-mounted Transducer Deployment System from Humminbird, the transducer is lowered beneath the keel, to sweep a circle around the boat for a high-res view in all directions.

The most recent development in fish finders, aside from CHIRP, is the high-resolution side- and down-looking imaging that is rapidly supplementing the traditional sonar view. The power of side- and down-looking sonar lies in the narrow fan-shaped beam that records the subsurface features by assembling narrow, overlapping scans. This is what provides the photolike image and the intense level of detail. (For a detailed look, go to As such, a scan beam requires a specialized transducer.

The traditional 50/200 kHz transducer is still the backbone of a fish-finding system, and in some cases, a single transducer can handle it all.

In many cases, the top-performance benefits of combined high-res side- and down-scan and traditional sonar come when you add a second transducer — or transducers — to your hull. Here’s a look at some of the options and transducer requirements.


Simple Option

Raymarine’s entry into down-looking sonar came with the diminutive Dragonfly, a 7-inch sounder/GPS plotter designed to give small boats expanded sonar capability. Dragonfly incorporates both CHIRP sonar and high-res DownVision. Raymarine is manufacturing its own transducer, the CPT-60, that’s included in the box. You won’t need a separate transducer for the two sonar modes: The CPT-60 handles both CHIRP sonar and ­DownVision view, and allows display of both images at once on the screen. This specific transducer that comes in the kit is the only option available. “We’re ­making our own,” says Raymarine’s Jim McGowan. “It’s a transom mount, with four elements, one big one for the ­25-degree traditional sonar and another horizontally aligned triple-stack array for DownVision — which uses long, horizontal ceramics — for a 60-degree wide and 1.4-degree signal.”

There is some choice in mounting the transducer: It’s available as a ­transom mount or a bracket mount on the ­trolling motor.


High Power

The Lowrance Elite 7 also supports a single transducer and provides ­Navico’s broadband sonar and DownScan imaging in a single transom-mount transducer.

Stepping up in functionality, the ­Lowrance HDS Series and Simrad NS Series offer StructureScan, the same high-res view as DownScan, which also looks to the left and right of the boat. Structure-​Scan requires an additional transducer.


So for the complete set of sonar ­functions, you’ll need a transducer for the traditional broadband sonar picture, and an additional StructureScan transducer — or a pair. For larger boats and V-hull installation, Navico and Airmar have developed through-hull StructureScan transducers and a Y-connector to link a pair of them, providing a complete left-to-bottom-to-right view in high resolution.

For smaller boats, where shooting around a keel is not a consideration, Lowrance makes its own transom-mount StructureScan transducer.

Both StructureScan and broadband sonar support a range of Airmar through-hull transducers.


Look Around

Humminbird, one of the pioneers in high-resolution side-looking sonar, now offers down imaging, side imaging and traditional sonar imaging, with a single proprietary skimmer transducer. It’s available with both a transom-mount and trolling-motor-mount option.

The latest from Humminbird, 360 Imaging, sweeps a complete high-res image circle around the boat, covering 1.6 acres, says Humminbird, with a 300-foot beam width, scanning 150 feet front, back and sides. In order to see 360 degrees, the transducer needs to be below the hull and motor, which is accomplished with Humminbird’s ­Deployable Transducer. A single model works with Humminbird’s 798 CIHD, 898SI, and 998SI through 1198SI sonars.

The deployment system mounts to the boat’s jackplate, or between the outboard and the transom. It needs to be lowered beneath the hull to work, but it is fully functional simultaneously with the other high-res and traditional sonars, and displays in split-screen. It functions from a dead standstill up to 8 knots. Move faster than that, and an alarm goes off, reminding you to either slow down or raise it to run.

Sonar Curtain: This rendering ­illustrates the relative difference in coverage between the curtain of side-looking high-res sonar, and the bottom coverage delivered by down-looking high-res.
Raymarine’s proprietary transducer for the new Dragonfly incorporates both conventional-view CHIRP sonar and ­high-res DownVision in the same housing.
Add a ’Ducer: The Lowrance HD2745 transducer enables side-looking ­StructureScan.
Humminbird’s Deployable Transducer for 360 Imaging.
All Arounder: With the transom-mounted Transducer Deployment System from Humminbird, the transducer is lowered beneath the keel, to sweep a circle around the boat for a high-res view in all directions.

More Gear