GPS chartplotters, depth sounders
In this page we will discover 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're going to see the characteristics of some of the most popular devices, such as the fishfinderLowrance, the fishfinder Humminbird, the fishfinder Furuno and the fishfinder Garmin. But let's go in order: what is it, what is it for and how to read a fishfinder?
Fishfinder: what is it?
For millennia, sailors have used sounders to measure the depth of seas, lakes and rivers. These long ropes have a weight at the end. In this way, the sailors of the past could understand the distance between the keel and the seabed, so they could 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 ultrasonic ecometer 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 works, in fact, is not difficult. Or at least, it is not excessively so. In extremely simple words, in fact, we can say that this device - once mounted on the stern of the boat - sends signals in the direction of the seabed. These signals, emitted continuously, go to 'bounce' on the bottom, then returning to the probe, so as to establish precisely not only the distance, but also the shape of the seabed and the presence of any obstacles for the boat. This is only true of the most basic devices - the so-called depth gauges. With the advanced models, however, you can get a lot more information, such as data about water temperature and the presence of fauna. The choice of the fishfinder must therefore be made according to the actual use that will be made, evaluating the power, the type of transducer and frequency. Who is dedicated to fishing trips, therefore, will have to buy specifically a fishfinder, which can provide much more information than a basic depth gauge.
The fishfinder allows the display of the seabed on board the boat through the use of an element called transducer, or a special probe that - as mentioned - transmits and receives signals via sonar technology. By operating 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 may be the seabed, or even seaweed or fish. Either way, they will bounce back and be picked up by the transducer. From here they will pass to the amplifier and then to the display.
Immediately below we are going to find out what are the different types of devices on the market, from the gps fishfinder onwards. We want to anticipate, however, for completeness, that different models work differently: the more powerful an echo-sounder is, the greater the level of the image returned to the display. Looking instead at the frequencies, we can say - in general - that a frequency of 50 kHz is used to create a wide cone, while the 200 kHz is used to form a cone of signals narrower, but able to return an image with a higher definition. It should not be forgotten, however, that there are models on the market which - to ensure at the same time width, depth and precision - are based on the simultaneous reading of double or quadruple cones, thus presenting to mariners an exceptional result.
The sonar signal
Let us briefly examine the type and function of the signal emitted by the echo sounder - or rather, the transducer. These are sound waves which, emitted from a single point, progressively 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 size from one model to another. Let's consider the most typical single cone transducer, which operates at a frequency of 200 kHz: the resulting cone will have an angle of 20 degrees, and will therefore be rather narrow. Now let's try to imagine how this same transducer could work in very shallow waters: 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 separate cones, so as to offer a large monitored area, even in shallow water.
But why does the frequency of the cone generated by the transducer also determine the angle of the resulting cone? To understand this we must think of the sound signal as such. It should be pointed out that bass, that is, low frequency sound signals, propagate more easily in space, leaving high frequency signals behind. The problem, however, is that as the frequency drops, the cone widens, generating errors in the reception of the signal. Something very similar can be said about the signal power: if it is too high - especially in shallow water - it can cause interference between the different signals, compromising the reading.
What types of fishfinders are there on the market?
Before buying a fishfinder it is good to get informed about all the possibilities presented by the market. And no, we do not speak only of a Lowrance fish finder rather than of a Garmin fishfinder. We talk about the type of device. As you can see yourself on the pages of our e-commerce dedicated to the world of boats, nowadays there are gps fishfinders or even cartographic fishfinders, which - as their name suggests - present to the user information on the depth and on the state of the seabed in addition to those related to the geographical position of the boat. Therefore, if we can look - in a simplistic way - to a gps sounder as a sounder added to a course plotter, looking at the chart sounder we find ourselves in front of a sounder with navigable charts.
Rarely is a chart sounder superfluous, so buying a chart sounder is always a good move. It should be noted, however, that sometimes the lightness with which this device is purchased makes it unnecessary during navigation. In some cases, in fact, you end up buying models with exaggerated powers, or perhaps to couple the wrong transducers to fishfinders that are also excellent: these and other factors can lead to an incorrect or unsatisfactory operation of the device as a whole. For this reason, we repeat once again, it is necessary to choose the most suitable device according to the characteristics of your boat, as well as according to your actual needs.
Which echo sounder to choose for your boat?
The size and type of the boat and your budget for the purchase are factors that must obviously be taken into account to understand 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, tends to install the fishfinders very simple, and then frequently opt for simple depth gauges. This is because, having bulky keels, you want to carefully monitor the shallow water, without expecting much more. For those who want something that goes beyond the simple monitoring of the depth of the seabed is necessary to move on more advanced models, or on the real echo-sounders, also called - not surprisingly - fishfinders. These devices, in fact, can get to give crucial information about the fish swimming in the observed area, starting from their depth, to get to their size and speed of movement.
The portable echo sounder
However, there are not only fixed fishfinders. No: if you have a small boat, a boat without an electrical system or a canoe, you can opt for a portable fishfinder, which can be powered by a battery and works through a transducer to be connected from time to time. Of course, these models cannot offer the same readability typical of fixed devices, which in many cases have large displays.
How to read a fishfinder
We have therefore seen briefly what it is and how it works a fishfinder, as well as the main types that can be purchased. But it's one thing to buy a fishfinder, quite another to be able to read it! It should certainly be emphasized that the understanding of the images presented by this device is not as difficult as it might seem at first glance: just do a little practice to understand how the reading process is actually intuitive and even fun. To this, then, must be added the fact that nowadays almost all devices (from the Lowrance fishfinder to the Garmin fishfinder, just to name two brands) are equipped with an LCD display, which, for the same size, returns an image of high quality - and therefore very readable. Unless you're thinking of buying a used fishfinder, then, you'll probably always have to deal with highly readable devices. So how do you read a fishfinder?
Certainly each brand represents a world apart, but despite these we can say that who learns to read a Lowrance fishfinder will not have big problems in understanding how to interpret the images returned by Garmin, Humminbird and Furuno models, and vice versa. Generally speaking, we can start by saying that the viewer presents a two-dimensional image, which tells us in a rather clear way the line of the bottom. But that's not all: as fishing fans know, on the screen we can also see some particular lines, or better, some arcs: those are the fishes swimming in the waters under the boat, which are graphically represented in a different way according to their tonnage and speed.
A fast fish, therefore, will be represented graphically by a small arc - better: a U - narrow, to underline its fast movement. A slower fish, on the other hand, will be recognisable by a wider U.
How to mount the fishfinder to your boat
Often people ask how to mount the fishfinder, when in fact they are referring to the installation of the transducers. It should be noted that there are different types of transducers, suitable for different solutions and boats. Transom transducers, for example, are designed specifically for small to medium sized powerboats. As their name suggests, they are mounted on the stern, at mirror level, using a special bracket. As you can guess, their installation is extremely simple, not leading to the drilling of the hull. The installation is slightly more laborious, but it is essential in the case of sailboats, which do not offer a mirror suitable for their installation. There are also other types of transducers, decidedly less common, such as trolling motor devices, transducers to be installed on the bottom of the hull and adhesive ones.
Chirp, Down vision and Side vision
In recent years, the market for these devices has experienced 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 the others? Well, essentially, apart from 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 made it possible to go beyond the dual-frequency devices: instead of being limited to 2 predefined frequencies, a fishfinder with Chirp function goes to embrace a wide and diverse range of frequencies, so as to return a detail before unheard of, which can only astound those accustomed to traditional transducers. In short, those who want to give the most to their fishing trip can only buy a device with Chirp function.
But that's not all: in the most advanced models you can also find the Down vision and Side vision functions. The Down vision function is everything that fishermen have always dreamed of, but have never dared to ask: it is in fact an option made possible by an innovative type of transducer, which - operating well beyond 400 kHz - allows you to frame in detail the bottom, even better than the simpler Chirp function. If with Chirp you can 'imagine' the seabed, with Down Vision you can actually see a photographic image of the seabed. Even this technology, however, has a limit - at least for now: beyond 50/60 meters depth it is practically useless. As the name suggests, instead, the Side Vision option allows you to look not under the transducer - and therefore not at the base of the cone - but at its sides. And not for a limited area: we are talking about 200 meters to the right and left, always with a very high image quality (by virtue, again, of the very high frequencies of use).