Echo sounders, or as they are sometimes called “fishfinding echo sounders”, enable the fisherman to “penetrate” through the water column and understand whether it is worth catching fish in a particular place of the reservoir. As a matter of fact, the device itself does not look for fish. It only shows everything that happens under the water surface – the relief and depth, the structure of the bottom and various water bodies.
Analyzing the information received, the fisherman understands whether he needs to spend his own time and freeze in a section of a reservoir with a flat sandy bottom, or move to a much more attractive place, where a sharp-toothed predator may well be waiting for him among the algae in a pile of pitfalls.
Functions and principle of operation of the echo sounder
As you can see, the main function of the echo sounder is not to directly search for fish, but to save the fisherman’s time spent on fishing by indicating the places where there are most likely no fish, as well as those where it is most likely to be. Therefore, the name “fishfinder” is fundamentally wrong. The fisherman is looking for the fish directly, and the echo sounder only receives and emits wave signals in order to subsequently display various pixel combinations on the screen.
Why do you need to know how this device works? First of all, in order to choose the required model and then get the most out of it for the upcoming fishing. So how does an echo sounder work?
The echo sounder transducer, also known as a transducer, in most cases, is installed on the boat’s transom and sends an ultrasonic pulse into the water. The impulse is reflected from the obstacle, returns to the echo sounder, which transforms it and displays the data on the screen. It should be remembered that the downward divergence of the cone is cone-shaped, and the depth of penetration of the beam and the width of the view directly depend on the angle of this cone.
Angle of view, pulse frequency and fish finder use
How does the radiation frequency affect the beam width? Undoubtedly, the higher it is, the narrower the emitted beam will be. So, for example, a frequency of 83 kHz creates a cone with an angle of 120 degrees, and a frequency of 200 kHz creates an angle of approximately 60 degrees. Naturally, a narrower, and therefore more “dense” in frequency, the beam penetrates much deeper. And it should be remembered that the more significant the depth, the larger the diameter covers the echo sounder beam directly at the very bottom.
Just imagine, at a depth of about 10 meters, the pulse divergence angle at a frequency of 83 kHz will turn into 120 degrees, as a result of which the diameter of the beam coverage in the layer at the bottom will turn into 34-35 meters. Think, but will the unfortunate device be able to display all this information on the screen?
Not too clear? Then imagine – you are sitting and trolling a pike on a medium-sized wobbler in rather muddy water. The fishfinder shows on the screen a very attractive hole directly under the boat with fish in it. How does it work in practice? As a matter of fact, the pit may well be eight meters to the right or left of the boat. Where it leads? The fish, most likely, will not see the wobbler from such a distance, and will not feel its vibrations. Thus, you see the fish, but it does not bite, because it simply does not see or feel the wobbler.
What conclusions can be drawn from this situation?
Firstly, it is advisable to use an echo sounder with a low radiation frequency and a significant viewing angle only when it is required to comb large areas, for example, to survey an unfamiliar place.
Secondly, an echo sounder with a small viewing angle and a sufficient radiation frequency allows you to get more accurate information about what exactly is happening right under the boat, as well as in its immediate vicinity. In this way, you can easily find the pit, curb or jar you need.
Thirdly, the closer to the water surface the echo sounder shows the presence of fish, the closer to the boat’s course of motion this fish is.
Fourthly, a single-beam echo sounder may well help out on fishing, and therefore it is possible to chase the number of beams, but it is not at all necessary.
Dual-beam echo sounders
As a matter of fact, dual-beam echo sounders are very different from each other. So, for example, the sensor of some of them is simultaneously capable of emitting several beams – one wide, the other narrow. Moreover, a narrow beam explores the bottom, and a wide one serves to expand the horizons.
Other echo sounders allow their owners to change the pulse frequency in several modes, which allows you to configure the device for multiple tasks. In this case, only one beam will work, but you can always make a choice at your own discretion. Moreover, different manufacturers may call this technology very differently.