Marine Electronics can be broken down into a few major categories but the screen on our MFD that is most important when it comes to locating, tracking, and targeting the fish we seek is the “fish finder/sonar” page.  Sonar can be an overwhelming category to many fishermen – so in this article I will cover the basics of fish finders, sonar, the displays we use and, most importantly, transducers. I will also offer my opinion on the most productive setups modern technology has afforded the inshore and offshore fisherman. The blue and red boomerangs we dream of marking are just one spoke of a larger wheel.  That being said, however, it’s what we all focus on and hope to master when it comes to marine electronics and angling as this real time, live data is the most important localized intel we can capitalize on while targeting our catch.

The ideal modern set up right now consists of either a R409LWM or CM411LWM big and large 2kw CHIRP transducer. They have an Ultra Wide 40 degree beam angle at low!  In 200ft of water that is over 146ft of circular bottom coverage. In 2000ft of water that is 2180 ft of coverage!!!! This also has a fairly narrow Medium CHIRP element array which will give you unbelievable bottom detail and target separation off the bottom in all depths and targets. Medium CHIRP just finds a way to mark bait better than anything else as well. I would then find a High Wide transducer in a housing that can easily added to your boat. This will give you the detail and coverage needed to effectively target fish while trolling, jigging, chunking, popping and keeping your lures or bait in the strike zone. This combo, consisting of three different frequency ranges in many beam angle shapes, would then be plugged into the industry’s leading black box/ module style fish finder which on the biggest and highest resolution screen possible all three would be displayed.

The rest of this article will explain exactly what all of the above paragraph actually means in an easy to comprehend format.  I hope this article not only helps you understand your boat’s setup and how it actually works but also helps you maximize your fish finders performance and is a catalyst to future improvements and upgrades. The fish finders and transducers we select to have onboard should be looked at as a top priority that will, overall, add up to more bent rods. Money spent on a quality fish finder paired with a quality and technique specific transducer is money well spent.

What is SONAR?

SONAR stands for Sound Navigation And Ranging. This a method of detection of  underwater objects and for measuring the depth below the transducer by producing sound waves or pulses and then measuring the return of the sound waves or pulses after being reflected.

Sonar was actually first used by Leonardo da Vinci when he placed a tube into the water and realized he was actually able to listen to different things in the water. This is called passive sonar. What we use in fishing is referred to as active sonar. Active sonar not only listens for these different sound waves and pulses but actually sends the sound waves and pulses from what is called a transducer. This transducer has the ability to both send and receive the sound waves and basically decode the signal using today’s modern modules to populate the image of that boomerang shaped tuna 200 feet below the boat onto the MFD screen.

This method of SONAR we use for fishing uses a few main components. A transducer for sending and receiving a signal like an antenna, a fish finder or hardware/software that powers the transducer decoding that signal, and a monitor/display  to show us our findings. I like to relate this three part fish finder system to a camera. Lens (Transducer) , Camera (Fishfinder) , Film (Monitor/Display).

The Film

Things like brightness measured in Nits, size, resolution, customizability of the screen, are all large brand to brand and price point selections of monitors/displays that will help determine the performance of your system.  My suggestion is to choose the largest, tallest, highest resolution touch screen you can fit and afford. A larger, taller and higher resolution display gives you the most data possible. Keep in mind we are looking at a column of water, so the more pixels we can have vertically on the screen the more data can be shown. Think of the clarity that a new HD TV offers us today compared to that type of image the standard definition TV afforded us.

The Camera

Brand to brand, each major manufacturer has both black box/ module style fish finders or MFDs with fish finders built in. Today’s built in fish finders are unbelievably good right now. In the past year alone, fish finder technology has exploded. Feature filled MFDs and fishfinders are hitting the market below past price points. Dual channel CHIRP, side stuff, down stuff, forward stuff, video game stuff, 3D stuff, the list goes on.  The ultimate question becomes is it worth upgrading to a black box/module style fish finder and leaving the built in one behind? The answer is built in style fish finders are great and upgrading to a black box or module is not always necessary.

That being said – does a car sound system sound better when the speakers are plugged into a stereo or when wired to an amplifier? Transducers are sending a receiving and receiving a sound signal. So why not put the thought into what is driving that sound?

Choosing a “fish finder” or what will drive and process your transducers findings, will ultimately determine the performance of your transducer. Generally, black box/module solutions offer the best performance. These are required when using 2kw or 3kw transducers but can increase the performance of 1kw or even 600w transducers tremendously. This not will only increase the performance of the transducer you have but will open more doors to customizing your system, with more settings and independent source control to enable you to get more dialed in.

Choosing a “camera” or fish finder that is correctly matched to the transducer or transducers you are using but is also jammed packed with customization and a plethora of manual and automatic setting selections is the only way to go. Choosing the best fish finder will maximize and fulfill the peak potential of your transducer and systems performance. Choosing a fish finder with push button and knob control options for the settings (add a wired remote if necessary) will help you in adjusting your settings to fit the type of  technique specific fishing you are doing. A camera with easy to use menus and options for fine and coarse tuning, will always provide a better picture compared to one that lacks those attributes and captures an out of focus, blurry and useless picture.

The Lens

This is where I will focus most of my attention. Transducers,or the lens we choose, are to be correct for the picture we are trying to take and should match the hull and style of how you fish. Understanding the lens you have will give you a better understanding of why a picture looks one way or the other. And why some pictures capture everything and some have parts that were just outside the frame.

You can go out and buy the most expensive camera on the market or the hottest most popular fish finders/monitors/displays money can buy. But if you do not pair and purchase specific lenses for your new camera or specific transducers for your new fish finder/monitor/display, you will not be able to capitalize on the valuable and sometimes limited time we have to fish.

If you are trying to take a picture of an insect or bird next to a specific flower, you get a certain type of lens. If you are trying to take a picture of a goat on the other side of the ravine, then you get a certain type of lens for that. Same goes for fish finders and their equivalent transducers. If you want a picture of the bass hanging above some structure in 15 feet of water there are certain transducers that work great for that. If you want to see a 400 pound broadbill bang his face into the mud chewing on snake mackerel and squid in 1900 feet of water there is a certain transducer for that as well. So not only matching the transducer to type of hull that you have but also matching the type of transducer you get for the type of fishing you plan on doing is very important. Transducers are designed in many shapes, forms, frequencies and power outputs. Choosing the correct one for your type of fishing is of most importance. Money is much better spent in selecting and installing a proper and  quality transducer, compared to just buying the best MFD/ fish finder on the market and using the old “lens” or transducer you already have.

Transducers are a device that send and receive a signal from pressure, heat, sound and even light and convert that into an electrical signal. That electrical signal is sent to today’s modern multi function displays or fish finder/modules and  then sends that to a monitor/display to show what is below the boat.

The “ducers” we use offshore that send and receive the SONAR signal are made in many different housings. Comprised out of bronze, steel, plastic, rubber or urethane but what they all have in common is that they all contain Piezoceramic Elements. These can be round and disk shaped or long and skinny, cylindrical or tubed. They can be large or small and even grouped together to work as a team. These ceramic elements resonate and oscillate to send a signal and then listen for the return of that signal. Being these sound waves or frequencies move at predetermined and  known speeds, the transducer sends this sound signal that it receives to the MFD or module and is able to then “do the math” and calculate, how deep the bottom is or paint that picture of thermoclines and fish beneath the boat.

Transducers are only as good as the location it is installed. You can have the best transducer on the market but if it is installed incorrectly or if you choose a poor location of  installation or the wrong housing, the performance of your setup will be just that – wrong.

The phrase “being in the right spot at the right time” is hugely important when it comes to your transducer. So do not only spend time deciding on the frequency or power of the transducer you choose, but spend the time in selecting the correct  type of housing for your style boat and the prime location of installation.


Power is important because this is how much signal you’re putting on the target. 600w, 1kw, 2kw, 3kw?  Think hitting a wall with a sledgehammer as opposed to only a roofing hammer. Sometimes we need a sledgehammer to break through that wall or boom down a deep low-frequency signal to mark bottom or bait down deep. But sometimes, all you need is a light tap.

More power will always increase your systems performance at depth.  More power can also help while shallower. The more sound or signal we put on a target, generally speaking, will yield crisper and cleaner returns. By increasing the power of the signal we send, we also increase the power or strength of the returns we receive. Stronger and crisper returns equal darker more pronounced marks on your fish finder.

But sometimes too much power is just too much. Keep in mind we are sending a sound signal.  Think whispering with a 600w ducer compared to the boom of club speaker at 3kw. We can scare the fish!

Frequency and What it Means and What is CHIRP?

What we have all used for years when it comes to transducers is what we call “tone burst”. That 50/200khz ducer you have, sends or “bursts” a single frequency down to the sea bed floor and listens for the return of that single frequency.  This single frequency is “shouted” down to the sea bed floor. However, thanks to modern technology, we have progressed from “shouting” a single frequency to having the chance at putting our ducer to work in harmony with a range of frequencies. This has provided crisper, cleaner, more pronounced returns  that were once only dreamed of. So what is this new technology? CHIRP.

CHIRP stands for Compressed High Resolution Radar Pulse. This technology gives you better target resolution,  better target detail, better target separation and better depth penetration compared to traditional broadband tone burst transducers.  This is all done by sending a range of frequencies over a broader bandwidth compared to just one single frequency. Putting more signal on a target and in turn, bouncing more data back to the transducer and your fishfinder.

Understanding different types of frequencies will aid you while inshore, midshore or offshore and hopefully help in choosing the correct frequency for the type of fishing you are doing.

Higher frequencies offer us the highest amount of detail, are used generally higher up in the water column and generally have a narrow beam angle. Lower frequencies offer the lowest amount of detail, are used lower in the water column and have a generally wider cone angle.  Medium frequencies are the “Goldilocks” frequencies offering a high enough amount of detail, not too wide nor too narrow beam width and can be a great all around choice for inshore, midshore and offshore. All around is great but how do we focus on detail?

Certain frequencies reflect off certain pieces of bottom or species of marine life better than others. Frequency will be a large factor in the image you see because the frequency is directly correlated to the beam angle of the transducer we are using and the detail reflected back.  If a beam angle is too wide or too narrow for the targets we seek or the detail is not the highest available we will ultimately limit the systems performance and undermine our ability to pinpoint and locate what is going on not only around us but directly underneath our boat. Last thing any of us wants is to possibly miss schools of bait or thermoclines in an area and not effectively mark small, compact air bladdered, fast moving fish like tunas. Believing a wreck loaded with fish is directly below us when it is really 50 ft off the port while in 120 ft of water can lead to less than desirable outcomes.

In recent years, High Wide CHIRP has taken over the market. High Wide CHIRP takes the highest frequency range available offering the greatest detail with a very wide beam angle (a constant 25 degrees) and the sensitivity and capabilities of no other transducer. This High Wide element offers a highly detailed, wide angled, data filled image for depths to 500ft. When properly installed this allows the angler to see things like a jig or weight slightly above a school of bait.  With its wide and detailed signal it can expand and pronounce a school of small sand eels or squid that may have been missed. It provides those picture perfect marks of the species that are being targeted. The wider cone angle succeeds while trolling, jigging, popping or chunking but is not good for bottom fishing.

A narrower higher frequency is best for bottom fishing. Narrower will offer better bottom detail. Think of what you can see when shining a spotlight into the woods as opposed to a flood light.  The detailed and focused nature of a spot light will offer more pronounced bottom, allowing you to pick up fish along a ledge or notice the slightest change in structure that the flood light might shine a shadow against or not light up. Check out below the difference beam angle makes.

Shapes and Sizes

Transducers come in many flavors manufactured in three main types of housings: first is in-hull, second is transom mount and third is thru-hull. These categories can each be broken down into more diverse and customized applications. Understanding this and selecting the best housing of transducer for you hull will directly result in your system working or not working. Cavitation, or the population of air bubbles on the face of a transducer, are the ultimate destroyer of fish finder systems. Selecting and installing a transducer that mitigates those air bubbles and has clean smooth contact with water is what works. The signal loss that in-hull ducers offer (although the best when properly installed) at tracking bottom at speed are poor choices for highly detailed fish finder images. The medium which works best for a transducers sound waves to transmit is water not fiberglass so any transducer in contact with water is usually best. Transom mount transducers offer a cost effective way at adding side stuff and down stuff but are not ideal for that “blue and red” fish finder. However, just like in-hulls, transom mount ducers offer affordable methods of adding technique specific transducers to a boat. Keep in mind a majority of “fishing” is done at speeds where a transom mount ducer is not affected by air bubbles.

Time and time again I hear stories of people complaining about how poor the performance of their fish finder is and they blame it on the transducer they have. More often than not I find that the transducer is not installed in the proper location or the type of transducer housing was not correct for that type of boat or hull. Invest time in not only finding the ideal location  to install a transducer to track bottom effectively at cruise. But also figure ways to add transducers to your boat that operate at different frequencies and beam widths so that you cover not only the whole water column below your boat but more importantly open your eyes to what is around you.

Tuning your sonar

Today’s modern electronics have some great auto features and using them exclusively is not the end of the world. Don’t be afraid to start at auto – you can always adjust from there. Also, don’t be afraid of clutter. Clutter is your friend when it comes to a fish finder. What depth are the fish holding?  Where is the thermocline? What direction (up or down) fish are moving and what does the bottom look like? Are the fish held together tight or spread out? Are they glued to the bottom or suspended? What type of bait is around? All these question relate to having clutter, or what I like to call “detail”, so it is very important.

I like to start at tripling the depth that you are currently in. Then let’s play around with the color – first the pallet. This can be more of a Chevy versus Ford thing but during the daytime I like a blue or white background. At night I like a blue background. Choose what you’re comfortable with. On a side note, modern side stuff and down stuff advancements have added another layer to the offshore fisherman’s quiver when it comes to live data on the screen. The pallet colors can be very important deciphering between structure and locating actual fish. Generally speaking the copper tones work  better at locating structure and the blue/green tones work better at marking bait/fish. But let’s leave all the down stuff and side stuff for another day.

What about bottom color? You want to turn this up and get a dark hard return on the bottom that were on.

When it comes to adjusting your radar, fish finder, or actually any settings on any type of device we want to be patient. Don’t start adjusting settings in drastic different measurements. Make small, fine adjustments and see what that adjustment does to the image. Make a change then let the screen cycle and see what actually changes.

The next adjustment is the gain. We’re going to turn this up until we begin to see solid bottom and, more importantly, a solid double or sometimes even triple bottom return. Don’t be shy of gain.

Remember patience.

Having a good solid bottom and a good solid second bottom return is going to let us know that we have the gain set properly. Once the gain is set properly we can do two things. We can re-adjust our depth back to the depth we are fishing or we can leave the screen set so that we can review that double/ triple bottom return. Sometimes a double bottom return is the best way to tell what type of bottom your fishing. Once you have that double bottom return properly set and your gain is right you can use this to tell if you’re on hard or soft bottom. Generally speaking, your “double” returns makes this more visible. Hard bottom looks darker and crisper. Softer bottom will look lighter and less pronounced on your double return. This is because that sound wave is either being bounced off a hard bottom or being absorbed by softer bottom and may be the difference between understanding if you’re on top of a muddy bottom, while looking for swordfish or a hard rocky bottom while bottom fishing for species like tog.

Ping speed

I generally like ping speed to be turned up putting more signal on the target. Think of throwing a tennis ball off a wall.  When the ping speed is low we’re throwing a single tennis ball and when the ping speed is set high we are using a machine to shoot lots of tennis ball more rapidly or signal more quickly at that wall or wreck.  And in return we’re receiving more detail.

Scroll speed

Scroll speed is basically how fast the image on your monitor/display is moving right to left. The faster the boat is going the faster you want your scroll speed. The slower your boat is going the slower you want your scroll speed. A faster scroll speed at higher speeds will help elongate smaller marks on the screen and make them more visible. A slower scroll speed at rest will help in not giving you a false looking giant tuna marks on your fish finder when you’re drifting over a school of seabass, for instance, giving you a true image of what is below you.

Time variable gain or TVG

This setting can be named many different things brand to brand and allows you to eliminate or add clutter, which I call detail, on the top 1/3 of that screen. Mastering TVG is huge when it comes to offshore fishing. This comes down to pixels on the screen. If we have screen with 1000 pixels vertically TVG allows us to optimize that screen when fishing shallow or deep. So don’t be afraid to adjust your TVG depending on the depth you are fishing and the depth your are targeting.

Noise rejection

This has to do with ambient noise that may be populated on your screen from things such as poor DC grounds or multiple transducers operating at the same frequency on board your vessel. Adjusting this setting will help in eliminating false or too much too little data, or “fuzz”, populated on your display.

In Conclusion

Practice makes perfect. When inshore bass fishing try to watch your screen as your crew drops jigs or reels in fish.  Try to understand what a mark on the screen looks like and means. Do not be afraid at displaying multiple frequencies. Change settings and try zooming in to the depths you are targeting. Remember to adjust when you change your tactics.  Use a 600w transducer for inshore to stay stealth. Find a frequency and setting that works for your type of fishing. Find a camera that is simple and easy to use, yet offers many settings and controls. Find a transducer (or transducers) that will focus on the shot you are trying to take and gives you options when the scene changes,  Location, location, location. Invest time in finding that sweet spot.

When looking for structure or bottom detail, switch to a narrow, higher frequency range. When deep dropping use the most powerful, lowest and widest channel you have. When trolling, jigging or chunking, use multiple beam widths and frequencies so that you don’t miss a thing. If you can only have one, then choose a system that does what you do most.  We all do a little of this type of fishing and a little more of that type. At the end of the day, all of these fish finder setups do their job, but if you take the time to not only buy yourself the new camera and lens, but learn how that camera works and which lens to choose when faced with a certain scenario, you may be able to capture that one image that changes the trip.

For the purpose of this article I have included below a chart that highlights the most productive uses of some of the most common and top of the line transducers that are offered. I have excluded in-hull and transom mount options. What you will see is that similar frequencies and beam widths are available in many shapes and sizes.. This folds over to In-hull and Transom mount as many of the transducers listed have exact twins in different forms. You will notice as power increases beam widths generally get more focused and narrowed.

Fishfinders are one of the captains best sources of information while on the water providing real time data of what is happening. Understanding how they work and the differences between the models and options available, choosing and adjusting your system correctly based on the style of fishing you do, should lead to more bent rods.

******Information gathered for this article and chart was found on The products and technology discussed is a registered trademark of  ©Airmar Technology Corporation


Matt Feeney works for Win-Tron Electronics located in Manasquan, New Jersey. Win-Tron Electronics is a marine electronics wholesale distributor, selling marine electronics to boat builders, boat motor dealers, marine electronic installers, e-commerce companies and commercial marine businesses throughout the world. He is fortunate enough to have the hands-on experience of living marine electronics day in and day out. Matt has countless hours on the water testing the industry’s leading marine electronic products. OpenBow.Org is extremely grateful to Matt for donating his personal time and dedication to help us deliver professional level knowledge direct to our network.

Editor’s Note: The purpose of “Ask a Pro” is not to confuse but to provide legitimate opinions from a variety of professionals that test their equipment and techniques on a regular basis. While there may be quite a lot of information to filter through – remember – this is not a “forum” with “armchair fishermen” commenting on the latest and greatest gear. We want you to TRUST our information!!! As a result, our mission is to be professional angler driven and provide you with the best information possible. We are confident that any of the gear or techniques discussed in our “Ask a Pro” series will increase success the next time you fish. Fish the Front!!!