A short introduction
Before we dedicate ourselves to the fish finder test on page three of this article, we would like to introduce the basic functionality of fish finders on the first two pages. A good understanding of fish finders is a prerequisite for an informed purchasing decision. Otherwise, you might easily sink several hundred dollars into a bad choice. It is essential that the depth finder is suitable to your own local water—it would be a waste if exciting new functionalities are missing or you overpay. Once the sonar is mounted, it will be impossible to exchange it.
Another reason why it is important to educate oneself is the information gap between dealer and customer. The customer wants to spend as little money as possible on the functions he needs. The retailer, on the other hand, has to make a sale. Great new functions are always advertised, regardless if those might add value or not. Only a few anglers know which functions are suitable to their contexts. The latest functions are never cheap. Of course, if you are indifferent and willing to spend big, then sure, go for the most expensive fish finder.
If the budget matters
If you have to stick to a budget, you must close the information gap between you and the dealer. That is essential to (1) select the right functions, and (2) paying a fair price. The money you save by purchasing the most suitable can easily amount to several hundred dollars. You can allocate that money to other purchases, maybe a new boat or rod.
This article will give you get a good overview of the basic fish finder functionalities. For a blog post, this article is quite long …
Afraid to get sold on a bad fish finder?
To help you get an advantage over the dealer, we recommend the book “The Ultimate Fish Finder Guide.” Over more than 150 pages you gain in-depth information on depth finders that will help you to at least close the information gap. You might even become superior.
Never rush the purchase of a fish finder. Yes, research takes a bit more time and money, but in the end, your decision will be more informed. If you buy the right sonar, you will save money and will have a lot more fun and success fishing.
So, on page one and two we introduce the basics. On page three, you will find 21 fishfinders in comparison, all divided into different price categories.
This article consists of 3 pages:
Page 1 – Basic requirements when buying a fish finder – You are here
Page 2 – Fundamental fish finder functionality – Click here
Page 3 – The top 21: Our ultimate fish finder comparison – Click here!
What’s important when looking for a fish finder?
Many anglers have only one goal in mind when using a fish finder: find fish so that they can cast bait and reel in their catch. Unfortunately, the best fishing gear on the planet won’t help you if you’re fishing in empty waters. A fish finder is meant to help you increase your catch rate and reduce the time you spend looking for fish (and – let’s be honest – have more fun with the sport). Anyone in the market for a new fish finder would likely hope for no less. But a depth finder can do much more than most people think, and a quick look at the display isn’t always enough to fully understand what’s going on under the water’s surface. That’s why it’s important to ask yourself a few questions before buying or using a fish finder:
- What am I looking for? Hotspots or fish arches?
- Am I after fish near the bottom or in open water?
- How deep is the body of water I’m fishing in?
- Will I also be using my fish finder on vacation?
- Will I be using my fish finder in ocean waters?
- Do I need my depth finder to identify various underwater structures and objects?
- How much can I spend on a depth finder?
- Do I need a mapping function with GPS?
We’ll answer a number of these questions in this article (and more in our Fish Finder Blog – Tips section).
Depth finders and fish finders in 2019
There have been all sorts of new developments in 2019. For instance, genuine CHIRP functionality has fallen even further into the mid-range price segment. We recommend that every potential buyer considers CHIRP when buying a fish finder. Contemporary fish finders even display HD ground imaging, temperature, thermocline, depth, and information on whether fish are located at the surface, mid-depth, or at the bottom.
Interpreting the images displayed by the fish finder is often the most daunting obstacle for most anglers to overcome. A fish finder’s display certainly isn’t easy to interpret, because the exact position of fish is only discernable when using certain features (such as SideScan or Garmin’s Panoptic). However, in most cases (we estimate that traditional 2D sonar is used over 90% of the time), you can’t precisely determine the position of a fish or hotspot near the bottom.
Additionally, fish finders produce ambiguous shapes of the fish, so that nobody knows for sure what is actually underwater.
Only with knowledge can we correctly determine the fish species and the location. Professionals draw from years of experience to make the right judgments.
This small elitist group of about 20% of anglers, hooks roughly 80% of the global fish catches year after year. All this despite often being cramped next to one another yet still catching one fish after the other.
A layman, who is on the water only a few days a year, can only watch in amazement, wondering what he is doing wrong. Of course, that’s not all bad as most other anglers on the lake only have limited experience as well.
We can recognize recreational anglers by the fact that from dawn to dusk, they seem to drive aimlessly from one spot to the other.
If you don’t feel like going days without a catch, you have to build up your knowledge advantage. Those who study will eventually graduate from the 80% layman to the 20% fishing pros. That’s the only way to be in the right spot at the right time more often.
A fish finder does not have to be complicated
Read here how the pros use their fish finders to catch 80% more fish with only 20% of the settings.
An overview: What to consider when buying a fish finder
Which features are important to consider when choosing a depth finder/fish finder?
Taking our combined experience into account, we’ve put together a ranking of the most important features available in today’s fish finders. We recommend choosing your next depth finder/fish finder according to the following criteria:
CHIRP means better identification of fish, period. At certain frequencies, fish can only be distinguished as individual bodies when there is enough (and sometimes quite large) space between them. CHIRP makes it possible to distinguish individual fish arches, even when the fish are tightly grouped.
Our second consideration would be affordability. CHIRP definitely takes first place in our list of priorities, but all other features are less important than overall cost.
If you want at least reasonably bathymetry (underwater topography) and to be able to find ground depressions, there’s only one solution: a narrow as possible aperture angle.
Without a map on your fish finder, you’ll have next to no chance of finding and marking the best hotspots. Many manufacturer-specific mapping functions display depth while your boat is moving and offer an awesome overview of drop-offs and underwater hills! GPS also offers increased safety, especially during the best time to fish: when dark clouds gather overhead. If you can afford a unit with mapping and GPS functionality, the investment is definitely worth the money.
In bright sunlight, a high-contrast display can make a world of difference out on the water. Without one, you’re unlikely to be able to see anything on-screen, rendering your fish finder useless. A display’s size and resolution are responsible for the level of detail reflected in the reproduced image. A quality transducer can deliver plenty of details, but the display ultimately has to be able to communicate them to the user.
In our opinion, having 2 combined frequencies (dual beam) isn’t as useful as having independently selectable ones. Being able to choose allows you to tailor your settings to the current situation rather than having a one-size-fits-all solution. It’s also important to note that the various frequencies often employ different aperture angles.
Which features are nice to have when choosing a depth finder/fish finder?
Dual beam is a common feature on fish finders in the budget and mid-range price segments. The technology combines the benefits of two different frequencies and displays the results on-screen simultaneously. The narrow aperture angle of one frequency produces a detailed bathymetric scan, while the relatively wide aperture angle of the other frequency scans a larger area to locate fish. The downside is that you can’t accurately distinguish the distance between the fish and your boat (see our ebook “The Ultimate Guide to Fish Finders”). As these are the days of CHIRP, dual beam tech is starting to lose relevance. However, this feature’s wide aperture angle is still useful when trolling.
Fish finder imaging features are great: they allow you to observe the world beneath the water’s surface with almost photorealistic clarity. However, we have to distinguish between imaging sonar directed below your boat (Down Scan, Down Imaging, etc.) and imaging sonar directed outward from the sides of the boat (Side Scan, etc.). Horizontally configured sonar is seriously cool – it allows you to pinpoint the locations of the best fishing spots without wasting any time, which isn’t the case with downward-facing variants. We’ve categorized this otherwise indispensable feature as “nice to have” on account of the price premium it entails. For many anglers, a depth finder/fish finder with Side Scan is simply too expensive to justify.
Seeing as they are intended for depths of up to 820 ft (250 m), 500-watt fish finders are more than sufficient for the vast majority of European fresh water fishing locations.
Wi-Fi is hip and trendy, and it allow you to transmit the details from your transducer for display on a larger tablet. In effect, you can save on the cost of a higher-quality fish finder display if you’re able to bring a tablet onboard with you.
Fish finders can be divided up according to the quality of their image reproduction and fidelity, usability, and user-friendliness. Technical details like the number of transmitters/transducers/oscillators, output strength, display resolution and the width of the transmission cone coverage (transduction cone) are the most important points when looking for the best fish finder to buy. Some depth finders are even rated for depths of up to nearly 3,300 ft (1,000 m). Lowrance claims a depth specification of a whopping 3,000 ft (914 m) for their Elite9x-CHIRP fish finder. However, it should be clear to everyone that at that kind of depth, readable fish arches are no longer part of the picture – a 50 kHz frequency just doesn’t allow for that kind of fidelity. However, it can help you find potentially interesting spots to fish near the bottom. Let’s be honest, though: who among us is actually fishing at those depths?
Depth finders/fish finders in review: The fundamentals
As we recognize it in sonar fish finders today, sonar technology was developed during the Second World War as a means to locate enemy submarines. Soundwaves are transmitted through the water at a velocity of roughly 1,440 m/s and are subsequently reflected by obstacles they encounter; the reflected soundwaves are then collected and converted into an electrical signal which can be interpreted. In essence, a fish finder is merely one of many kinds of depth finders in existence. A traditional fish finder transmits a conical soundwave field downward into the water. These so-called “2D frequencies” are then used to calculate depth and bathymetry (underwater topography). A transducer emits multiple pulses in sequence (that familiar “ping…ping…ping…”) in order to carry out this kind of measurement. The signals expand out into a cone as they proceed toward the bottom of the body of water. Depending on water depth and the signal’s exit angle, the soundwaves come into contact with obstacles (such as objects in the water or the ground) and are then reflected back toward the depth finder with corresponding strength. The soundwaves which are collected by the transducer at the water’s surface are then processed by the fish finder and converted into an image that the human operator can evaluate.
One of the most important aspects here is the way in which the fish finder’s screen displays information. With a traditional 2D sonar unit, the current image is displayed on the right side of the fish finder’s LCD screen; the image moves progressively to the left as information is updated. As a result, you can only view images of the past (i.e. what is already behind your boat)! Naturally, this setup requires some adjustment in terms of your fishing technique.
So, you want to know which fish finder features are “must-have” and why? To find out, download free pages of our fish finder guide here! Download
Depth finder/fish finder output: What about the wattage?
The higher a fish finder’s wattage, the more powerful a signal it can transmit. It’s a given that higher wattage is a bigger concern in the USA than it is here in Germany. The reason for the difference is simple: in the USA, there are a substantial number of fishing competitions with prize money reaching into the millions. Consequently, the performance requirements are much higher when every second counts, as that performance is directly tied to how much money the angler stands to make. Here in Germany, competitive fishing is against the law in most federal states—even where it is legal, most competitions are more like a local club outing (complete with participants sitting around the water’s edge). But back to wattage: a unit’s watt-output is specified in “RMS”, which stands for “root mean square” and indicates the average output of all transmitted frequencies. The specified wattage dictates the strength of the signal which is sent into the water. The deeper the water you’re fishing in, the higher your wattage should be. You should also go for higher wattage if you’re planning on using higher frequencies, as they require more energy to penetrate to the same depth as lower frequencies. Think about what happens when you call out to a friend: the farther away they are, the louder you have to yell to be heard – even more so if you have a high voice.
The RMS specification is the most important number to look at when shopping for a fish finder, as it’s not possible for the manufacturer to fudge the numbers in the same way they can with other specs (like peak-to-peak output). Even mid-range sonar sounders like the Humminbird Helix 12 CHIRP MEGA SI GPS have an RMS of 1,000 watts and an impressive peak-to-peak output of 8,000 watts. On the other hand, inexpensive devices like the Garmin Striker 4 have an RMS of 200 watts; even so, the less expensive unit can transmit at depths in excess of 1,300 ft (400 m), while the Humminbird specifies its maximum transmission depth at 400 ft (122 m). Here it becomes clear what matters most: what do you want to do with your fish finder? Any given unit will adjust its output (wattage) according to the depth being scanned. In still waters up to 160 ft (50 m) in depth, a wattage rating of about 100 W is perfectly sufficient. Deeper or choppier waters mean that you’ll want to pump up your wattage accordingly.
Which frequency is best when using a depth finder/fish finder?
A transducer is placed underwater and transmits high-voltage impulses (in the ultrasonic range) downward. On their way to the bottom, these soundwaves come into contact with obstacles (e.g. individual/schools of fish, branches, objects suspended underwater, or—at the latest—the ground) and are reflected back toward the fish finder’s transducer to be collected. The fish finder’s software then processes the received signal and converts it into an image which is displayed on-screen. In this process, it uses the received signal to calculate whether a given underwater object is a fish, a branch, or hard/soft ground.
Most fish finders operate in the 2D sonar range: frequencies between 50 and 200 kHz. A 200 kHz wavelength is significantly shorter than one at 50 kHz (ultrasonic wavelengths range from 7.5 mm to 30 mm), which means that an image produced at 200kHz will be much more detailed than one produced at 50 kHz: more soundwaves come into contact with the object in question and are reflected back up to the transducer.
Most people underestimate the importance of using the correct sound wave frequency: it can have a significant impact on whether a given spacing between fish results in them appearing to be a single fish on-screen. The difference can be massive: at 50 kHz, fish that are closer together than 50 cm simply can’t be distinguished from one another. This is directly dependent upon distance resolution and should be a point of interest for anyone who owns or is looking to buy a fish finder. In our book, we go into great detail on the subject of distance resolution.
Tip: If you have trouble visualizing the way sound waves work, take a piece of paper and draw a set of points 3″ (7.5 mm) (200 kHz) apart in a straight line. Next to that line, draw another line of points spaced at 12″ (30 mm) (50 kHz). Now, put an object (like a key) next to the points: as you can see, more points with 3″ (7.5 mm) spacing fall along the object than those spaced at 12″ (30 mm). This is the same principle that applies to the frequency on your fish finder (shorter wavelength = higher sonar sounder frequency).
Benefits of low-frequency fish finders
On the other hand, there are benefits to low frequencies, as well. Because 50 kHz has a relatively long wavelength, the water offers accordingly little resistance, and the signal can penetrate deeper than a high frequency signal can. A low-frequency signal also does a better job of determining ground quality and characteristics, as the soundwaves penetrate deeper into the ground before being reflected upward. This is particularly important when fishing at depths greater than 650 ft (200 m) (e.g. in Norway). At those depths, 200 kHz soundwaves often won’t reach the bottom of the fjords, which means that there won’t be any echo at all. As a result, you’ll be left with an empty display and no useful information of any kind.
Pros: 200 kHz
- Highly detailed images and information
- Recognizes small objects/obstacles
- Generally narrow transmission cone, gathers information better at depth
- Tightly grouped fish are displayed as individual fish arches
Cons: 200 kHz
- Small transmission angle, scans a small area
- Doesn’t gather information outside the transmission cone
- Not intended for deep waters (over 500 ft/150 meters)
Pros: 83 kHz
- Depth sounder gathers information over a large area (generally a 60° transmission angle)
- Can be used in deep waters
Cons: 83 kHz
- Less detailed information about the scanned area
- Schools of fish are often displayed as a single large, dense group of points
- At greater depths, there is excessive information that can’t be displayed
What is the best transducer aperture angle to use with my fish finder?
A transducer’s crystal is responsible for the frequency transmitted and the aperture angle of the resulting soundwaves. Said another way, at what angle do the soundwaves leave the transducer? The crystal bonded to the transducer is usually round and coated on two sides with an electrically conductive material. A crystal rated at 200 kHz/20° has a diameter of 1″ (2.5 mm). These crystals get smaller every year, but their miniaturization is ultimately limited by the laws of physics.
What does this kind of crystal look like, and what practical difference do different size aperture angles make?
Many commonly available fish finders operate at a frequency of 200 kHz and have an aperture angle of 20° to 28°. At a depth of 33 ft (10 m), soundwaves emitted at a 20° aperture angle hit the bottom with a diameter of 11.5 ft (3.5 m), which equates to a surface area of about 100 sqft (9 sqm). For reference, 100 sqft (9 sqm) is roughly the size of a small bathroom. At a depth of 33 ft (10 m), a crystal with an aperture angle of 60° produces a soundwave that grows to 38 ft (11.5 m) in diameter by the time it reaches the bottom.
This means that the fish finder scans an area of 1120 sqft (104 sqm) – roughly equivalent to the area of a large apartment. Let’s take the opportunity to put these numbers into clearer perspective. Imagine a 1120 sqft (104 sqm) apartment on the second floor of a building. There’s a pike located in that apartment’s kitchen. Your fish finder is located on the fifth floor, pinging and relaying the resulting image to you above the water.
A fish, 33 feet (10 meters) down
Whoa! The depth finder display is showing a large fish arch at a depth of 33 ft (10 m). What now? Get out your bait and cast? Hold on a minute – we only know that the fish is 33 ft (10 m) down. The depth finder can’t tell us if it’s in the kitchen, the bathroom, or some corner of the living room or another. We’d have to cast off in multiple directions and hope that we happen to land somewhere in the pike’s vicinity – and that it happens to be in a biting mood at just that moment. Choosing the right frequency and aperture angle is incredibly important in a practical sense. If you want to get out on the water, find fish, and *BAM* hook a three-feet-pike, you should know that a high-quality, affordable fish finder isn’t enough on its own. Depth sounder systems are often misunderstood in terms of their complexity and physical limitations.