Your Own Sonar System: A Comprehensive Guide To Fish Finders

Your Own Sonar System: A Comprehensive Guide To Fish Finders

Some will say that part of the joy of going fishing is that you never know what to expect, while others will tell you that it’s the worst part of the hobby. Anglers tend to be fiercely divided over the smallest of topics, and heated debate is far from uncommon when fishers gather together in any meaningful numbers.

It’s likely that you’ve seen anglers argue about the pros and cons of saltwater and freshwater fish, rivers vs. lakes, fishing from a boat vs. fishing from land or a dock, and much more. One of the more intense debates that you will come across when speaking to fishers is the place of technology in the hobby.

Of course, this depends on what kind of technology you are referring to, as a boat is technically a piece of technology. In our case, we mean devices like fish finders and other aids that make it easier for you to fish and that many old-timers will deride as being an unfair implement to fish with.

Fish finder on a boat.

Over the course of today’s article, we are going to be examining fish finders in detail, and by the end of the guide, you’ll be an expert on them. From what they do and how they do it to the different types of fish finders on the market, we will have you covered.

What Is A Fish Finder?

As you may have guessed from the name, a fish finder is an electronic device that is designed to help you find fish while you are fishing. In the past, the only way to find fish was using your intuition. You needed to have some experience to know where to find the hotspots.

A fish finder will display the fish below, around, or in front of your boat, and it can be a beneficial tool when the water is murky, or the conditions are unfavorable. Of course, it is likely that you are wondering exactly how these tools work in the first place.

How Does A Fish Finder Work?

A fish finder (which can also be referred to as a fish detector) uses the same concept that is used to navigate submarines: sonar (which stands for SOund Navigation And Ranging). While it may seem complicated, sonar is a rather straightforward concept.

Sonar works by projecting a wave of sound into the water and waiting for it to hit something. When the sound wave impacts a solid object underwater, it is reflected back at the sonar emitter (known as the transducer) which detects the return of the sound wave.

Behind the scenes, your sonar is calculating the speed of the sound wave that was emitted and then dividing it by the amount of time that it took to return so you can get an idea of the range. It is for this reason that many fish finders will display more than just fish, including the topography of the bottom of your body of water.

Fish finder, how it works.

Of course, a fish finder uses a sonar system that is much weaker than the one that is used by attack and strategic submarines. In fact, if you were right next to a sub in the water when it emitted an active ping from its sonar, the 230-decibel sound would likely severely injure you or worse.

Types Of Fishing Sonars

Traditional Sonar

A traditional sonar display will provide you with bands that look like thermal hotspots so that you can detect the fish with greater ease. This is the closest form of sonar to the variety that most people are acquainted with in movies in and TV.

Keep in mind that traditional sonar is harder to use for beginners since you have to learn how to interpret it. This kind of sonar is a little more complicated than the circular display with a sweeping arm that most people expect when they hear the word.

Down-Looking Sonar

Sonar that looks downwards will give you want is essentially an image of the seafloor directly beneath your boat. The fidelity with which the image is rendered will depend on the frequency of your scans as well as the quality of the screen on your fish scanner.

This form of sonar is often coupled with side-looking sonar since they each cover the blind spots of the other. Unfortunately, all but the most advanced sonar rigs won’t be able to display down-looking and side-looking sonar at the same time.

Parts Of A Fish Finder


The transducer is the most crucial part of your fish finder as it is responsible for producing and capturing the waves of sound that make sonar detection possible. A lot of the time, the transducer will be sold separately from the fish finder because most varieties tend to be compatible with each other.

You will have to consider the ideal frequency for your transducer, and many of them also feature dual-band capabilities so that you can quickly switch between frequencies.

A low-frequency transducer will have an easier time penetrating deeper into the water, but it will provide a less detailed image. It is for this reason that low frequency is often used for shallow applications, even though it can technically go further.


The display is the part of your fish finder that is responsible for rendering the data into something that you can perceive. There are both black and white as well as color displays, though the former has largely fallen into disuse due to the convenience of being able to color-code data.


You will also need a mount for the transducer and sometimes even the display. The choice of mount for your transducer will depend on what you are trying to do with it; you can mount one on the bow of your boat, or you can fix it to a pole so you can sweep it over the side.

Fish finder mount.


As you can see, fish finders are products which are not overly complicated, and they’re relatively simple to understand once you know the basics. Feel free to leave a comment down below and let us know what you think.