Choosing a transducer is an important part of designing your sonar system.
The sonar image on your display starts with the transducer, so its
characteristics greatly affect the performance of the system. With so many
different technologies, transducer selection may seem mystifying. The main
points to consider are how will it be mounted, what views do I want and what
frequencies do I need.
- How will it be mounted?
- Most inland water boats are fitted with a transom or a shoot-thru-hull
broadband sounder™ transducer as well as a second broadband sounder
transducer on the bottom of the trolling motor, if equipped. Today, a
transom mounted StructureScan HD® transducer can be found on most inland
- Most bay/flats/offshore boats are fitted with a transom mount or a
- What views do I want?
- Broadband and CHIRP can be accomplished with the same transducer—the
difference is how the signal from the transducer is processed by the sonar
- StructureScan HD requires a different style of transducer
- SpotlightScan requires a dedicated transducer mounted to a
foot-controlled trolling motor.
- What frequencies do I need?
- Here is a quick breakdown:
- Low CHIRP or 50kHz—Lower frequency means higher power for deep-water
- Medium CHIRP or 83kHz—Specifically designed to give the widest
coverage area, 83 kHz is ideal for watching a bait under the transducer
in shallow water.
- High CHIRP or 200kHz—Higher frequencies display a higher resolution
image making it easy to discern fish from structure or structure from
- 455kHz—Built into StructureScan HD and SpotlightScan, 455kHz allows
for scanning of a large range with picture-like detail.
- 800kHz—Also built into StructureScan HD and SpotlightScan, 800kHz
yields less range but even higher resolution detail than 455kHz.
CHIRP sonar is cutting edge echosounder technology. Unlike the single
frequency of the Broadband Sounder technology, CHIRP continuously sweeps a
spectrum of frequencies. Sweeping frequencies makes two improvements to the
- Better target separation- Because CHIRP uses a range of
frequencies, rather than a single pulse, CHIRP sonar greatly improves the
ability to distinguish fish targets that are very close together or on the
bottom. Fish become easier to differentiate from the structure they are
- Less interference from errant noise that would have
been picked up by a single frequency sonar. CHIRP creates a unique range of
frequencies and listens for only those sonar returns, this gives CHIRP sonar
the ability to distinguish between what is a real echo, and what is just
extra disturbances bouncing around underwater.
Single frequency sonar—also referred to as Broadband—is commonly annotated
as 50kHz, 83kHz, or 200kHz. Broadband is essential sonar technology at its
finest. Broadband relies on pings and echoes from a single frequency. This
technology is great for tracking bottom, finding schools of baitfish,
displaying predator fish, and bait tracking.
StructureScan 3D features a multi-beam sonar technology ─ powered by an
increased number of transducer receiving elements ─ to create high-resolution,
180-degree, three-dimensional images of underwater structure and bottom
contours. Transmitting at 455 kHz, the transducer not only produces tru-to-life,
three-dimensional images, but also boosts the performance of two dimensional
DownScan and StructureScan HD imaging. StructureScan 3D scans can reach up to
600 feet to either side of the boat, for both 3D and 2D SideScan. It scans
depths of up to 300-foot for two dimensional DownScan™ Imaging.
StructureScan HD allows users to scan an area with a very high frequency
signal, producing picture-like images. 455 and 800kHz frequency selections
allow users to choose between 455 for scanning great ranges, and 800 for
close-in, higher resolution detail. StructureScan HD literally turns the sonar
paradigm on its side with the ability to search to the left and right of your
boat rather than only below. StuctureScan HD imagery can be overlaid on top of
cartography for a detailed, up-to-date view of structure in relation to your
position. Called StructureMap™,this is excellent way to find underwater
structure and changes in bottom layout.
SpotlightScan is boater-controlled directional sonar that allows anglers to
scan an area they are interested in fishing while on approach. For use with
cable-steer trolling motors, it aims two sonar signals similar to
StructureScan HD in a specific direction. An angler can view productive
fish-holding spots, such as drop-offs, channels, and underwater structure,
before positioning a boat over top of them making it easier to find and cast