Echo Fishfinder

• Guide to choosing the Garmin fishfinder

What is the echo sounder?

On this page we will find out how an echo sounder works, how to mount it, how to read it correctly and which type of echo sounder to buy according to your needs. Not only that: always here we will go to see the characteristics of some of the most popular devices, such as the Lowrance fishfinder , the Humminbird fishfinder, the Furuno fishfinder and the Garmin fishfinder. But let's go in order: what is it, what is it for and how do you read an echo sounder?

Echo sounder: what is it?

For millennia, sailors have used sounding rods, long ropes with a weight at their end, to measure the depth of seas, lakes and rivers. In this way, sailors of other times could understand the distance between the keel and the seabed, so as to be able to navigate in relative safety, without damaging the boat. Here, the echo sounder is, in fact, the maximum evolution of this very simple instrument: it is in fact an ultra-acoustic echo sounder device, which measures the depth of the sea through the emission of sound impulses.

Echo sounder: how does it work?

Understanding how an echo sounder actually works isn't difficult. Or at least, it's not too much. In extremely simple words, in fact, we can say that this device – once mounted on the stern of the boat – sends signals towards the seabed. These signals, emitted continuously, 'bounce' off the bottom, then returning towards the probe, so as to precisely establish not only the distance, but also the conformation of the bottom and the presence of any obstacles for the boat. This, moreover, only applies to the most basic devices – precisely called depth gauges. With the advanced models, on the other hand, it is possible to obtain many other information, such as data on the temperature of the water and the presence of fauna. The choice of the echo sounder must therefore be made on the basis of the effective use that will be made of it, evaluating the power, the type of transducer and the frequency. Those who are dedicated to fishing trips, therefore, will have to expressly buy a fishing sounder, which will be able to provide much more information than a basic depth gauge.

The echo sounder allows you to view the seabed on board the boat thanks to the use of an element called a transducer, or rather a special probe which – as anticipated – transmits and receives signals via sonar technology. By activating the device, therefore, electrical energy is passed to the transducer, which converts it into sound signals directed towards the seabed. The signals continue to propagate until they encounter an obstacle: it can be the seabed, as well as algae or fish. Either way, they will bounce and fly back to be picked up by the transducer. From here they will then go to the amplifier and then to the display.

Immediately below we will find out what are the different types of devices on the market, from the GPS sounder onwards. However, we want to anticipate, for the sake of completeness, that different models work differently: the more powerful an echo sounder is, the higher the level of the image returned to the display will be. Looking instead at the frequencies, we can state - in general - that a 50 kHz frequency is used to create a broad cone, while the 200 kHz one is used to form a narrower cone of signals, however capable of returning an image with higher definition. However, we must not forget that there are models on the market which - to guarantee breadth, depth and precision at the same time - are based on the simultaneous reading of double or quadruple cones, thus presenting sailors with an exceptional result.

The sonar signal

Let us briefly examine the type and function of the signal emitted by the echo sounder – or rather, by the transducer . These are sound waves which, emitted from a single point, gradually widen as they approach the seabed. For this reason, therefore, we can speak to all intents and purposes of cones, which as mentioned vary concretely in terms of size between one model and another. Think of the more typical single cone transducer, which works with a frequency of 200 kHz: the resulting cone will have an angle of 20 degrees, and therefore will be rather narrow. Well, now let's try to imagine how this same transducer could work in very shallow water: a single cone with this reduced angle would have very little chance of offering a wide enough image. It is no coincidence that there are more and more transducers on the market that offer two, three, even 6 distinct cones, so as to offer a large monitored surface, even in the presence of shallow water.

But why does the frequency of the cone generated by the transducer also determine the resulting cone angle? To understand this we have to think of the sound signal as such. It should be noted that basses, i.e. low-frequency sound signals, propagate more easily in space, leaving behind high-frequency signals. The problem, however, is that as the frequency decreases, the cone widens, generating errors in signal reception. Something very similar can also be said regarding the signal strength: if it is too high – especially in the presence of shallow waters – it can cause interference between the different return signals, compromising the reading.

What types of fishfinders are there on the market?

Before buying an echo sounder, it is good to find out about all the possibilities presented by the market. And no, we're not just talking about a Lowrance fishfinder rather than a Garmin fishfinder. Let's talk about the type of device. As you can see for yourself on the pages of our e-commerce dedicated to the world of boats, today there are gps or even cartographic sounders, which – as their name suggests – present the user with information on the depth and condition of the seabed in integration with those relating to the geographical position of the vessel. Therefore, if we can look – in a simplistic way – at a GPS sounder as a sounder added to a route plotter, looking at the cartographic sounder we find ourselves in front of a sounder equipped with a navigable nautical chart.

A fishfinder is rarely superfluous, and therefore buying a fishfinder is always a good move. However, it should be emphasized that sometimes the lightness with which this device is purchased nullifies its usefulness during navigation. In some cases, in fact, we end up buying models with completely exaggerated powers, or perhaps by coupling incorrect transducers with otherwise excellent echo sounders: these and other factors can lead to incorrect or unsatisfactory operation of the apparatus as a whole. For this reason, we repeat once again, it is necessary to choose the most suitable device based on the characteristics of your boat, as well as on your actual needs.

Which depth sounder to choose for your boat?

The size and type of vessel and your budget available for the purchase are factors that must obviously be taken into consideration when figuring out which fishfinder to buy. As we have already said, however, the first and fundamental discriminating factor is the use that will be made of that device. In sailing boats, for example, we tend to install very simple fishfinders, and therefore we often opt for simple depth gauges. This is because, having bulky keels, you want to carefully monitor the shallow waters, without expecting much more. For those who want something that goes beyond the simple monitoring of the depth of the seabed, it is necessary to move on to more advanced models, i.e. on real echo sounders, also called - not surprisingly - fishfinders. In fact, these devices can provide crucial information on the fish swimming in the observed area, starting from their depth, up to their size and their speed of movement.

The portable sounder

However, there are not only fixed echo sounders. No: those who own a small boat, a boat without an electrical system or a canoe can in fact opt for a portable depth sounder, which can be powered by a special battery and works through a transducer to be connected from time to time. Certainly these models cannot offer the same legibility typical of fixed devices, equipped in many cases with generous displays.

How to read an echo sounder

We have therefore briefly seen what an echo sounder is and how it works, as well as the main types that can be purchased. But it's one thing to buy a depth sounder, it's another thing to know how to read it! It should certainly be emphasized that understanding the images presented by this device is not as difficult as it might seem at first glance: it is enough to do a little practice to understand how intuitive and even fun the reading process is actually. To this, then, must be added the fact that nowadays all or almost all of the devices (from the Lowrance fishfinder to the Garmin fishfinder, just to mention two brands) are equipped with an LCD display, which, for the same size, returns a 'high quality image – and therefore very readable. Unless you plan to buy a used fishfinder, therefore, you will probably always be dealing with highly readable devices. So how to read an echo sounder?

Certainly each brand represents a world of its own, but despite these we can say that those who learn to read a Lowrance fishfinder will not have major problems in understanding how to interpret the images returned by Garmin, Humminbird and Furuno models, and vice versa. In principle we can start by saying that the viewer presents a two-dimensional image, which communicates the bottom line quite clearly. However, that is not all: as fishing enthusiasts well know, on the screen we can also see particular lines, indeed, arches: those are the fish that swim in the waters under the boat, which are shown in a different graphic way based on their size and speed.

A fast fish, therefore, will be graphically represented by a small arc – better: a narrow U – to underline its rapid movement. Another slower fish, on the other hand, will be recognizable by a larger U.

How to mount the fishfinder to your boat

People often ask how to mount the fishfinder, when really they are referring to installing the transducers. It should in fact be emphasized that there are different types of transducers, suitable from time to time for different solutions and boats. Transom mount transducers, for example, are specifically designed for small to medium sized motor boats. As their name suggests, they are mounted at the stern, flush with the transom, using a special bracket. As you can guess, their installation is extremely simple, not leading to drilling the hull. On the other hand, the situation is different as regards the through transducers, which instead require drilling: the installation is therefore slightly more laborious, but it is indispensable in the case of sailboats, which do not offer a mirror suitable for their installation . There are also other types of transducers, much less common, such as trolling motor devices, transducers to be installed on the bottom of the hull as well as adhesive ones.

Chirp, Down vision and Side vision

In recent years, the market for these devices has undergone a great evolution, leading to the creation of sensational models such as the Lowrance HDS-16 Carbon Row fishfinder. But what distinguishes the most advanced models from all others? Well, essentially, in addition to the quality of the screen, ease of use and readability, the innovation is to be recognized in their new features.

The main one is the Chirp function, which has allowed us to go beyond dual frequency devices: instead of limiting ourselves to 2 predefined frequencies, an echo sounder with the Chirp function embraces a wide and diversified range of frequencies, so as to return a detail first unheard of, which can only amaze those accustomed to traditional transducers. In short, those who want to give the most to their fishing trip can only buy a device with the Chirp function.

But that's not all: in the more advanced models you can also identify the Down vision and Side vision functions. The Down vision function represents everything that fishermen have always dreamed of, and yet never dared to ask for: it is in fact an option made possible by an innovative type of transducer, which - operating well beyond 400 kHz - allows to frame the seabed in detail, even better than what was done by the simpler Chirp function. In fact, if with this you can 'imagine' the seabed, with Down Vision, in fact, you see a photographic image of the same seabed. Even this technology, however, has a limit – at least for now: beyond 50/60 meters of depth it is practically useless. As the name suggests, however, the Side Vision option allows you to look not under the transducer - and therefore not at the base of the cone - but instead at its sides. And not for a small area: in fact we are talking about 200 meters to the right and to the left, always with very high image quality (once again thanks to the very high frequencies of use).