Transducer, probe, shoe, eye or sensor, works in relation to the fishfinder and sends/receives the ultrasonic signal to the bottom.

Types of transducers

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The fishfinder needs its own transducer to operate, which sends the ultrasonic signal to the bottom and receives it, then sends it back to the fishfinder in the form of an electrical impulse.

Transducers are distinguished by their installation mode:

  • Aft, is by far the most common because it represents the best compromise between economy, ease of installation and performance. In fact, the installation is simple (just fix it with 4 screws), but the stern area is one of the parts of the hull most subject to turbulence
  • Passante, is able to give the absolute best performance, but you are forced to make a hole in the hull with the consequent weakening of the structure and risk of sinking in case of impact.
  • Inside the hull, no holes should be drilled and the transducer will not be subject to fouling, but the sensitivity is reduced (commonly by 10%). It must be immersed in a container filled with water or vaseline and then sealed. It's an option only available for fiberglass hulls.

They are also distinguished by the material in which they are composed, all suitable for fiberglass hulls:

  • Plastic, is the most economical and most widespread solution. Not suitable for wooden hulls.
  • Bronze, is diffused for the passing model, in such case suggested because it is more resistant. In the case of wooden hulls is the one that best suits.
  • Steel, it is recommended for aluminium or steel hulls

Elements of a transducer

Today a transducer often has several elements inside, sometimes with different echo transmission frequencies, sometimes with the same frequency but oriented towards the bottom with different angles so that together they can detect a larger surface of the bottom.

For an echo-sounder it is important to detect the bottom with the widest possible angle of transmission, especially on shallow water, so that you can have a more complete perception of the bottom under the boat and not just the detail of the bottom under the perpendicular of the stern.

Some Installation Tips

The transducer must be installed in such a way that it remains immersed at all times. It must be considered that as the speed increases, the waterline rises from the water and the transducer must remain immersed even at the operating speed.

The transducer must be installed in such a way that it is always as parallel as possible to the water.
We have to keep in mind that the transducer must not only transmit the ultrasounds, but must also "pick them up" after the bounce from the bottom, if we tilt the transducer even a few degrees it will be difficult for the transducer to "pick them up".
It will therefore also be necessary to check the trim of the boat at the operating speed.

Before installing the transducer at the stern (but also sometimes through the transducer), a hydrodynamic study of the hull must be carried out to determine the area with the least turbulence. There are installation habits depending on the number and type of engines, but each hull has its own peculiarities and therefore there are no common rules.

Only install transducers recommended by the manufacturer. Otherwise, in addition to the loss of warranty rights, there is little chance that the transducer will fit perfectly into your fishfinder.
In fact, today the technical characteristics differ greatly from one manufacturer to another, and even the connectors are often customized.

Avoid cutting the transducer cable and splicing it. Each joint represents a potential loss of sensitivity of the fishfinder. In case it is really necessary, it should be performed by an expert.