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The Technology Behind The Working Of Fishfinders You Must Know

A Fishfinder is a device that is used to locate underwater objects like underwater debris and foreign objects. It is majorly used to find fish. Both the sports and commercial fishermen use these. Fishfinders are derived from “fathometers”. Fathometers are used for navigation, safety, and determining the depth of the water bodies. A Fathom is an astronomical unit for measuring the depth of water. These work on the echo system.

Sending a wave

As mentioned above, Fishfinder devices work on echo. An electric pulse is generated through the transmitter and it gets converted into a sound wave of a fixed wavelength by an underwater transducer called a hydrophone. That wave will then be sent into the water.

Reflection of wave

 If the wave sent into the water strikes any object or any particle, it gets reflected. It means that it is carrying information related to the depth, size, and shape of the object. The receiver then gets the data.

Information receiving and decryption

The processor and the calculations required will read the information received by the receiver. The final output of the information obtained will be displayed on the screen of the fishfinder in a format of an image. The accuracy of the device will depend on conditions like temperature, salinity in the water, and pressure in the water (depth dependent).

Calculations and principle

When a sound wave hits a body, it will be reflected at the same speed. By using this fundamental principle, we can define the depth of a water body.

Depth= (Time taken to receive the last echo/2) * speed of sound in the water

By using these formulae, the distance is calculated, and the processor processes images.

Types of Fishfinders

There are various types of fishfinders available in the market. We can choose a user-friendly fishfinder that meets our needs. At different price points, we get various special features in a fishfinder.

Commercial units

Fishermen and individuals widely use commercial units for their fishing business. These units also come with a strip chart recorder in which an advancing roll of paper can mark the depth permanently and can save it. These units are user-friendly fish finders because they are easy to control and can be mastered very quickly. The basic features provided in these units are:-

  • High frequency (shows fish, wrecks, and other small objects).

  • User controls

  •  Information is displayed in a detailed manner.

Naval units

Naval units are mainly used for military use. These units come with overpowered features like: –

  • Low frequency (deep ocean depth calculation).
  • Shallows (high frequency for small objects).
  • High chart speeds.

Standalone Fishfinder

If you want to know what’s there in the water, then these low-cost fishfinders will give you the best performance. These come with a more prominent display. If you are an occasional fishing man, then this standalone fishfinder is made for you!

Combination of Fishfinder/Chart plotter

These fishfinders are mainly for mid-sized boats. These come with a GPS for navigation. The display has two halves. A black box attachment can make a chart plotter into combo units by installing a transducer.

Networked system

These are the most advanced fishfinders and come with substantial data sources like radar, raster and vector GPS charts, video, and many more advanced features like Bluetooth, and WIFI (which gives a user access to the device from his mobile). Multiple displays can give one more access to information.

Features that you should pay attention to while buying a fishfinder

  • CHIRP Encoder:- Having a good encoder lets you easily change frequencies.
  • GPS map function:- Having a GPS can give you the best spot for fishing.
  • High-contrast, high-resolution display:- Having a high contrast display can give you vision even in bright sunlight.
  • Cone Angle:- A cone angle has a wide opening which gives you a better underwater image.
  • Portable vs Fixed:- Depending on your interest, you can buy a fixed or portable fishfinder. If you own a boat and you do frequent fishing, then go for a fixed one. If you are the type of guy who rents a boat to fish occasionally, then go with the portable fishfinder.
  • Symbol:- A unique symbol portrays different factors such as numbers, fish, surface, and rocks.

Pros and cons


  • Helps in knowing the depth of water bodies.
  • Helps find objects in the water.
  • Helps calculate the distance of objects in the water.
  • Helps in determining the shape of objects.
  • Speed of the object can be calculated by sending multiple waves.
  • Using a fishfinder can help catch a fish quite easily.


  • Results are often not accurate due to external conditions.
  • Few devices can’t pass through an object.
  • Sending high soundwaves can affect marine life.

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