Many of us, have some difficulty in understanding the functions and advantages of the various types of fishfinders and transducers, particulary when it comes to purchasing a fishfinder for the first time.

Hopefully the following information, will help with choice of purchase. Please feel free to contact us, if you have any further questions.

What is a Transducer ?

A transducer is a device that converts an electrical energy signal into an acoustic sound signal and in turn sends this signal to a target such as the lake or sea bottom or of corse fish targets and then receives it back again.
This signal from the fishfinder is applied to the transducer which then sends out the acoustic signal through the water. The transducer then receives the reflected echoes that the sounds waves encounter and they are sent as an electrical signal to your fishfinder. Your fishfinder then interprets this signal into an understandable visual display on your fishfinder screen.

A transducer will need to be installed on your boat in the most appropriate, convenient and effective position possible, taking into account disturbance from external objects, engine turbulance or length of the transducer cable.
There are 3 main transducer types available for varying circumstances and boat types, the most common one being the transom mount. Other transducer types are through-hull and in-hull (or shoot-through).

Sample picture of a garmin transom mount transducer, the tyep usually supplied with most fishfinders.

What is a dual beam transducer ?

The beamwidth on a transducer is the angle of the signal being sent down through the water - simular to aflashlight torch beam. The narrower the beam (e.g 60deg), the greater the energy and detail on the designated target, but requires less power required to send the beam. The wider beam (e.g. 120deg) requires more energy to send out the signal but can scan a much wider area that the narrower beam. A dual beam transducer is therefore capable of either narrow or wide angles which are usually selectable. e.g. Garmin echo 50 being dual beam at 60 and 120degrees.

Typical display showing how a dual beam transducer functions:

Wide Beam

When a wide beam is selected the frequency used on the transducer will be lower (around 77khz). The wide beam is best suited to deep water because water absorbs sound waves at a slower rate for low frequencies and the signal can travel further before becoming too weak to use. Because the angle of the beam is wider at low frequencies, the sound wave sent out is spread out more and so therefore more suited to a large viewing area under the boat. The downside of this however is that targets will have a lower definition and the returns will be more susceptible to noise. So although low frequencies can see deeper, they may not give you a clear picture of the bottom levels.

Narrow Beam

The narrower beam will use a higher frequency (around 200khz) and is better suited for shallow water - roughly speaking up to around 200 feet. You will get a more accurate reading using 200khz at a faster speed. Higher frequencies give you better detail for detecting smaller objects but over a smaller area of water. High frequencies also show the targets with better definition, showing less noise and less unwanted echo returns.

What is a dual frequency transducer ?

A dual frequency transducer or even multiple frequency transducer is one that contains 2 or more elements. The multiple elements are capable of running simultaneously so that you can get multiple returns at the same time. The Garmin Fishfinder echo 150C and echo 200 for example has a dual frequency transducer that contains 2 elements that can run at 50khz and 200khz at the same time. Some fishfinders such as the Garmin echo200 and echo 500c allow the two returns to be displayed on a split-screen display so you are able to see both the narrow (200khz) and wide beam (50khz) together.