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In just a bit more than one fishing season's time, CHIRP sounders have come out from Garmin, Raymarine, and the Navico group. The lawsuit (now settled) between Lowrance and Humminbird has brought attention to the 3-D imaging and side-scanning shallow water products that they have just introduced. Garmin purchased Interphase, which will likely result in powerful side and forward-scanning sonar to fit into the Garmin networks.

In the same timeframe, the commercial-grade sonars from Furuno have been revamped and the megayacht-sized Farsounder Forward Looking Sounders have won awards for their increased range and ease of use. At the shallow-water level, Lowrance 3-D fishfinders have been upgraded. There are other developments, too.

Should you wait for the dust to settle before you buy a new fishfinder? I never advise waiting since the technology seems to develop faster and faster and you'll fall farther behind the curve if you wait. Plus, these new sounders are a huge leap ahead of what was available before.

With these new fishfinders, you couldn't learn this much about what's under and around your boat if you parted the seas like Moses.

So, we'll look at the features and consider which apply to kingfishing.


By now you know that Airmar developed the new transducers that empower the CHIRP, Broadband, or Spread-Spectrum fishfinders. Of course, these are names for the same technology for processing very detailed information from a new breed of depth transducer. You can read the February 2012 Angler article for theory and general information, too. These transducers are a bit larger and carry a premium price, too. So you want to take a quick look at to select the style for your boat. The website is also loaded with documents to understand more about the technology itself.

Beside the choice of transom-mount, in-hull or through-hull, you can select frequency bands of high or low. Very much like before, you would pick the higher frequency range to hunt for kingfish in relatively shallow ocean water. However, using CHIRP, you will still be able to mark bottom in water that is nearly two miles deep. Different fish show better at certain resonant frequencies, but you're not picking a CHIRP frequency with that in mind. The whole point of CHIRP is that it uses a broad range of frequencies and your target fish will be on the screen along with the baitfish and bottom structure that have their own particular frequency ranges, too.

For very shallow, freshwater lake use, we'll look briefly at 3-D and some other considerations later in this article.

The CHIRP transducers have an ID chip in them that matches up to individual brands of processor and display, so you would buy the transducer with the black box, not from Airmar. Once you have a transducer in mind, you consider the black box, the package deal, and compatibility with your installed MFD (Multi-Function Display) screen and network. Raymarine offers a black box model of their ClearPulse or a choice of displays with the sounder box built into the display head.

The new and vastly improved detail of what is under your boat will be in all CHIRP brands, but the electronics manufacturers add varying features, so there's more to study.


Garmin calls their CHIRP by the name Spread-Spectrum and the black box is model GSD26. It is compatible with 4000, 5000, 6000, and 7000 systems, although you will remember from a few paragraphs back that you will need a new CHIRP transducer.

The GSD26 has a list price of $2,000 plus the transducer and the installation cost. Transducers run from $1,000 to $4,500 for the big, commercial-grade tanks. Garmin's website is a bit vague for something that is this radically new, but I think this topic is worth the study time and a visit to a good dealer and a Garmin booth at a boat show.

The GSD24 was announced at the same time as GSD26 about a year ago, and some people thought the GSD24 would be CHIRP. It is an improved GSD22, without CHIRP or Spread Spectrum Technology.

While the Raymarine CHIRP sounders use AutoAdaptive automatic adjustment to ping rate, frequencies, and power up to 1kW, the Garmin GSD26 allows you to manually adjust frequency range, and power from 300 watts to 3kW. You would have to practice with the adjustments because there are so many varying conditions, but the goal would be to recognize fish species and size. Be careful not to adjust away the fish you want to find in the first place. Of course, the Garmin can be put into automatic mode, too.


Raymarine's ClearPulse 450C has some cool features built on their advances in HD signal processing. Besides the automatic adjustments aimed at not missing any detail, if you are in deep water you may miss a very small fish target or baitfish that are too small to rate one pixel's width on your screen. With TruZoom, you are not just expanding the pixels that would be there anyway—TruZoom brings up more pixel detail in the zoomed image.

ClearPulse sounders are not compatible with most of Raymarine's previous screens since some of the processing power is in the MFD (multifunction display). Raymarine makes it clear in their brochures and website information, so you need to take a look if you are keeping your current network.

If you are upgrading to the newer, slimmer bezel displays, Raymarine makes some good-looking adapter trim pieces.


Navico's BSM-2 CHIRP sounder is a bit different to use than the touch screens on Raymarine and Garmin, but the menus, fine adjustment to color palettes and the scroll-back-in-time functions may be worth it. Again, the high resolution is in the technology of any CHIRP fishfinder, so it's a matter of your favorite brand or the detailed features and controls that will drive your decision to add CHIRP to your boat.

Once you move ahead to CHIRP, be sure to have your transducer installed correctly. Make the investment worthwhile.


Until there's an unforeseen breakthrough in digital processing that can overcome some basic laws of physics, there won't be a scanning sonar for an SKA boat. Similarly difficult, 3-D images of sounder signals from a rolling and bouncing boat are a smeared picture at best.

It's still worth your time to stay up to date on the Humminbird and Lowrance Structure Scan. They are designed for a boat on a relatively shiny-surfaced lake, where you are looking for fish hiding in sunken trees or off to the side in the shade of a bank or something. The Humminbird transducer mounts on a pole over the side, and that alone puts it in the league of electric trolling motors.

You can add more power to a 3-D sonar or side-scanning or moving sonar for deepwater ocean use, but you would then need a large vessel to hold it steady. To some extent the images can be smoothed electronically and on a large vessel a gyro compass would be connected, but it's out of our realm. The Lowrance LSS 2 is a step in the right direction, and it can see up to 300 feet to either side in ideal conditions. Perhaps a medium-powered scanning sonar will come out of the Interphase technology that Garmin has just purchased.

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