Buying a first or new sonar for a boat always turns into a difficult quest due to the abundance of technical specifications and marketing tricks of manufacturers. It is easy for a beginner who comes to the store to get confused with the acronyms CHIRP, DownScan, SideScan and various radiation frequencies that seem to be magic without proper preparation. However, understanding the basic principles of sonar allows you to choose the device that will reveal the underwater world and provide a stable catch, rather than becoming a useless toy.
Well-chosen sounder Not only can you show depth, but you can also detail the structure of the bottom, identify individual schools of fish, and even determine the type of soil. In this article, we will explore the key aspects of choosing from real-world water conditions, rather than advertising booklets, you will learn why frequency matters and how to save without losing functionality.
Basic principles of operation and types of sonar
A fundamental understanding of how the device works helps to avoid disappointment when buying. A classic 2D sonar sends a cone-shaped signal down, and the wider the angle of this cone, the more the bottom area is covered, but the less detail each object is covered. Modern models use the technology. CHIRPIt sends a continuous signal over a wide range of frequencies, allowing for clear separation of fish and bottom even at great depths.
There's also scanning sonar technology that creates a photorealistic image of the underwater space on the sides or just under the boat. It's not just a picture, it's a detailed map of the terrain, where you can see driftwood, grasses and individual predators. For a beginner, it's important to distinguish between these two modes: classical sonar gives information about the depth and presence of fish in real time, and the scanner allows you to study the structure of the bottom when you move.
It's important to understand that blindly following vendor recommendations can lead to buying redundant functionality. If you fish in shallow rivers, a powerful deep-sea appliance will not work properly without the right setup. Conversely, a simple budget option may not be enough for a clear picture for large depths.
⚠️ Note: Do not buy Ice-labeled sonars (for winter fishing) for installation on a boat without checking compatibility with GPS modules, as they often lack the necessary interfaces for mapplotters.
The differences in the frequencies of the radiation determine which fish you see, and the low frequencies penetrate deeper, but give a less detailed picture, whereas the high frequencies work great in shallow waters, showing the smallest details. The optimal choice for universal fishing from a boat is a dual-frequency sensor or model with support for broadband CHIRP radiation.
Selection criteria: frequency, power and viewing angle
When choosing a particular device, first consider the operating frequency range. Standard values for freshwater fishing range from 50 kHz to 200 kHz and above. Low frequency (50-83 kHz) is necessary for breaking through large depths, where it is not the detail that matters, but the fact that there is an echo. High frequency (200 kHz and above) provides detail, allowing you to see the separation of fish and the bottom even a meter from the ground.
The power of the emitter also plays a critical role, but it is important not to chase the maximum numbers. Power is measured in watts (RMS), and for most bodies of water of the middle hand is quite enough 250-500 W. Exceeding this parameter is justified only when trolling at speeds above 10 km / h or at very great depths over 30-40 meters.
The angle of view of the sensor is another parameter that is often ignored: a wide beam (60 degrees or more) is good for finding fish under the boat, but it smears objects around the edges. A narrow beam (10-20 degrees) gives accurate information about what is directly under the keel. sonar They often allow you to switch between the beams or use them at the same time.
- 🎣 For bottom fishing: Choose models with a narrow beam for accurate positioning of the bait.
- 🌊 To find active fish: A wide viewing angle or side scan is required.
- ⚓ For trolling: The priority is the screen refresh rate and signal power.
For boats where the angler's eye is minimal, the 5-7 inch diagonal is the middle ground. Large screens (9-12 inches) are convenient for splitting the screen into multiple windows, but require more space to install and more powerful power.
When installing the sensor on the transom, try to position it so that air bubbles from the screw do not fall into the signal reception zone, otherwise you will get breaks on the screen.
Scanning technologies: DownScan and SideScan
The revolution in the world of fishing electronics is the emergence of structural scanning technologies known as DownScan (Lowrance) or DownVision (Raymarine), which use high-frequency signals to create an image similar to aerial photography of the bottom. Unlike traditional sonar, which shows arcs, the scanner draws real-world contours of objects.
SideScan extends search capabilities dozens of times, sending signals to the sides of the boat, allowing the bottom to be "seen" up to 100-150 meters in each direction, ideal for finding eyebrows, sunken trees and large clusters of fish without having to swim directly above them.
But these technologies have limitations: Structural scanning works only at relatively low speeds, speeds of 10-12 km/h, and the picture starts to float, and the detail drops dramatically, and at very high depths (over 40-50 meters), the detail of the side scanning decreases, and classical sonar comes into play.
| Technology | Review | Best application | Limitations |
|---|---|---|---|
| 2D Sonar | Cone under the boat | Definition of depth, availability of fish | Small detail of the structure |
| DownScan | Underboat strip | Bottom relief, snags | Can't see fish above the bottom in the thickness |
| SideScan | Stripes on the sides | Search for points in large areas | Requires low speed |
| CHIRP | Improved 2D | Separation of fish and bottom | Requires sensitivity adjustments |
Many anglers make the mistake of relying on scanners alone, so the perfect sonar must combine both technologies.
Why does the scanner show the void where there is fish?
The scanners work at very high frequencies, which reflect poorly from fish swim bladders unless they have a dense scale or bone structure.
Sensors and methods of installation on the boat
The choice of sensor (transducer) is often more important than the choice of the head device itself. It is the sensor that generates the signal, and if it is chosen incorrectly, no processor will improve the picture. There are three main ways of installation: transax, in-body and cut into the bottom.
The transducer is mounted on the back of the boat (trans) and is the most popular and simple option, not requiring drilling of the hull. However, at high speeds or at high wave, the sensor can "catch" air, which leads to loss of signal. In addition, in inflatable boats PVC mounting must be especially reliable, so as not to damage the balloon.
The slash sensors are placed through the hull at the bottom of the boat, which provides the best signal, because there are no air bubbles between the sensor and the water, and there is no propeller turbulence. But the installation requires drilling holes, which is not always acceptable, especially for aluminum or fiberglass boats with complex bottom geometry. For metal boats, this option is often the only one working, because metal shields the transom sensor signal.
- 🛶 For PVC boats: Only a transom sensor with the possibility of quick-removal fastening.
- 🚤 For boats: preferably a cut-in sensor or installation in a special flask.
- ⚙️ For trolling: The sensor should be streamlined to minimize resistance.
Wireless float sensors are particularly noteworthy, and they are convenient for spinners who often change boats or fish from shore, but their autonomy is limited and their connection stability can suffer from severe interference or over long distances.
⚠️ Warning: When installing the sensor on the outboard motor, make sure that the vibration of the motor at idle speeds does not create a "porridge" on the sounder screen.
Integration with navigation and mapping
A modern sonar is most often a multifunctional device (MFD) that combines sonar, GPS and mapplotter. Being able to download detailed maps of water bodies makes fishing much easier. You can mark catch points, build routes and return to them with a meter accuracy.
The important aspect is support for map formats. Market leaders are Navionics cards, C-MAPs and manufacturers' own formats (Garmin BlueChart, Lowrance Chart). Before buying, make sure that the sonar you choose supports current versions of maps for your region. Lack of maps makes the navigator a simple coordinator, which is uncomfortable in unfamiliar terrain.
Integration with other devices opens new horizons: connecting the sonar to a tablet or smartphone via Wi-Fi allows you to broadcast an image to a large screen or control the device remotely, and synchronization with autopilots and electric motors with a GPS anchor, which allows you to automatically follow the routes of trolling.
The processor must be powerful enough to keep the interface running smoothly while using sonar, maps and navigation. Cheap models can hang around when switching between screens, which is annoying in dynamic fishing.
☑️ Pre-purchase check
Top manufacturers and popular models
The sonar market is divided among several major players, each with their own strengths: Garmin is renowned for its reliability and excellent maps, Lowrance (part of the Navico group) is considered a benchmark for anglers due to its clear interface and quality sonar. Raymarine is focused more on yachtsmen but has powerful lines for fishing, and Humminbird (Johnson Outdoors) offers advanced 360-degree viewing technologies.
For beginners, a series of fishing series will be a great choice. Garmin Striker or Lowrance HookThese models are devoid of the frills of touch screens and complex mapping, but they provide an honest sonar picture and reliable GPS. They are easy to learn and have an intuitive menu.
Professionals and boat owners are more likely to pay attention to the series Garmin GPSMAP, Lowrance HDS or Humminbird Helix/SolixThese devices support the installation of additional modules, have powerful processors and high-resolution screens, and they allow you to connect cameras, radars and engine control systems.
When choosing a brand, you should also consider the availability of service in your area. Complex electronics can fail, and the ability to quickly get advice or repairs is an important factor.
Don’t overpay for a touchscreen if you’re fishing in the rain and cold – physical buttons are much more convenient and reliable in such conditions.
Frequently Asked Questions (FAQ)
Do I need a side-scanned sonar for fishing on the river?
For narrow rivers with strong currents, lateral scanning may be less useful than for reservoirs, because the range of view is limited by the width of the channel, but it is great for finding eyebrows and sunken objects along the shore without coming close to them.
Can a sea sonar be used in a freshwater body of water?
Yes, it can. The principles are the same. But sea sonars often have sensors designed for salt water (hull materials), and their frequencies can be optimized for greater depths. On a shallow river, such a sensor can work incorrectly without manual adjustment.
How often should the sonar be calibrated?
Modern digital sonars do not require regular user calibration, but only once to adjust the sound speed (if high depth accuracy is required) and sensitivity to specific conditions. Automated mode usually copes well.
Does the water temperature affect the sounder?
Temperature affects the speed of sound in water, which can theoretically make a small error in depth measurement (about 1-2%). Most modern devices have a built-in temperature sensor and automatically make adjustments, so you do not need to do anything manually.
Why does the sonar show a double bottom?
This phenomenon often occurs because of thermocline, a sudden temperature drop at a certain depth that reflects the signal, and it can also be caused by too high sensitivity of the device.
To sum up, choosing a sonar is about balancing budget, boat type and fishing style. There is no one-size-fits-all device that works perfectly for everyone, but understanding your needs will make the right purchase. Investing in quality sonar pays off with increased catches and time saved to find fish.