Article by Capt. Steve Katz
When it comes to finding the best fishing grounds, some captains have that fifth sense. Such helmsmen can consistently navigate to productive waters using little more than visual observation of the conditions and a chart or two. On the opposite end of the spectrum, some captains will not leave the dock without the latest in high-tech gadgetry- Starlink, satellite images, altimetry data, multiple fish finding sounders and the like. For most captains, a happy medium that combines local knowledge with the right amount of technology guides their search for productive water. Once there, how do you know that the fish are there? Most of us use a finely tuned echo sounder. Others deploy the spread to see what awaits.
What if there was something even better, a way to “see” if there are any fish around your boat in real time?
Omni sonar works like underwater radar – you can think of it like something from the movie The Hunt for Red October. Omni style sonars include a transducer housing or sound dome that is lowered into the water from a storage tube within the hull of the boat. Technology has enabled the development of Omni sonar so that the transducer does not need to rotate mechanically to capture the 360-degree view under the boat. The Omni style Sonar consists of multiple stacked elements to transmit the sonar signal in all directions virtually simultaneously. The combination of the processing power of the hardware and the multiple sonar elements allows the system to provide a real-time image of the water around the boat. Yes, that means you can see fish targets swimming in and out of the sonar beam coverage area.
The Omni style sonar was originally designed for and used by commercial fishing boats. Once the Omni sonar was installed on sportfish boats and captains saw and caught more fish, word got out and it has become a must have for serious tournament sportfishing operations.
What does an Omni sonar get you? It allows a real-time picture of the fish, or lack of fish, around the boat. A traditional echosounder beam “looks” below the bottom of the boat and reports on the screen on the area you just passed over. The Omni scanning sonar can “look” around the boat, in a full 360-degrees with a range out to 1000’ or more, which gives you a coverage of 72 acres of underwater area.
While the Furuno Omni (CSH-8LMK2) is the most popular sportfish omni sonar, back in 1978 the Canadian company, MAQ designed and built the first Omni sonar for the commercial fishing industry. MAQ has expanded their product line since and offers sportfishing Omni sonar similar in size to the popular Furuno model. Additionally, Kongsberg Maritime introduced the Simrad SY50 omni sonar a few years ago. The SY50, built in Norway, is a more compact unit than the MAQ and Furuno with many modern functions within its windows computer operating system. While these three systems are different in design and operation, the result is similar - they all will “mark” anything that is not water.
If you are getting your tape measure out to see if you can fit one in your boat, these three units all use the same standard 8” diameter through-hull retraction tube. The hoist that raises and lowers the sonar transducer into operation sits on top of the retraction tube. While each installation is customized to fit the boat, the shortest omni style sonar requires about 54” +/- from the outside of the hull to the top of the hoist. Popular installation locations on a sportfish are forward in the engine room, below the steps leading to the staterooms or inside the cabin on a center console.
These Omni systems all have similar additional components such as transducer, transceiver, processor, and control unit. These are all “black box” type systems, which can use most any standard marine monitor to display the sonar picture.
The Furuno Omni transmits its sonar signal on a fixed frequency of 85 kHz. The beam angle, how far up or down the transducer “looks” can be adjusted from near zero – which is parallel to the sea surface to -55-degrees pointed downward toward the bottom. The Simrad SY50 operates with a standard operating frequency of 57kHz and the SY50 allows users to choose any frequency between 54 and 59kHz. The MAQ operates with a standard operating frequency of 60kHz or 90kHz, depending on the version purchased, with the ability to fine tune the frequency during installation.
The specifications include much longer ranges, though the practical application is dependent on water depth, wave heights and other factors. This Omni sonar allows you to change the tilt angle, something that cannot be done with a traditional echosounder. Increasing the tilt angle allows you to scan a more downward trajectory and a smaller angle allows you to focus on the top of the water column. All these scanning sonars use a stabilization component (motion sensor). This component calculates and compensates for the boat’s roll, pitch, and yaw. Proper stabilization of the image allows the system to draw the sonar picture relative to the vessel.
Omni scanning sonar can “look” around the boat, in a full 360-degrees with a range out to a few thousand feet, though regular trolling operation range is usually about 1000’. There are plenty of settings and adjustments that many captains and sonar operators fine tune thought the day. Practical application is dependent on water depth, wave heights, sea water temperature, and other factors. All these scanning sonars use a stabilization component (motion sensor). This component calculates and compensates for the boat’s roll and pitch.
As you might expect, an Omni sonar system is a significant investment in your boat. The basic components of a omni system begin around $75,000 and increase with required accessories, options and installation totaling up to around $150,000. The installation is comprised of two main phases, the fiberglass, wood and or metal work required to move components as needed make room for the 8” hole in the hull and the installation of the retraction tube, this is usually performed by a boatyard or boat builder craftsman. The second phase is the mechanical/electrical/electronic phase usually performed by the equipment dealer technician.
There is a learning curve when operating a scanning sonar compared to a traditional echosounder. Interpreting the results on the screen takes some practice. To fine tune your system, you will need to make some adjustments such as range, tilt and gain which are the most used adjustments used throughout the fishing trip. Other adjustments are not often needed throughout the day include transmit power, pulse length, TX cycle, noise limiter, color curve, horizontal and vertical beam width.
Technology that was once reserved for science fiction books or for hunting submarines is transforming the sportfishing space. It’s revolutionary technology indeed. §
