An Insight look into Transducers

One debate (or confusion) often heard among anglers is which transducer beam is wider or narrower or clearer. This article by Dale Ward will make it Gin Clear!

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Transducers

This article is to talk about Transducers and all that makes them work, including frequency settings on sonar and structure scan, cone angles on the transducer beams and the all new latest Chirp. To understand how a transducer works firstly is paramount, then you can start to understand how cone angles work to determine what frequency you should be running for your style of fishing.

Cone Angles

To understand how a transducer works I want to firstly explain how a transducer transmits a sound wave beam known as a “Cone Angle”. This is like a V shaped fan that shoots sound waves to targets and returns back to the transducer like a ricochet. The reflected signal is received by the transducer and is sent to the sounder unit to be processed into a more likely recognizable object on the screen. The signal that is sent out from the transducer varies in frequency. This frequency is set by you in the units settings. The most common sonar frequency settings are 50 kHz, 83 kHz and 200 kHz and more high definition Structure Scan frequencies can run larger amounts like 455 kHz and 800 kHz, but ill go into that in more detail below.

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A cone angle or beam angle determines the coverage of an area under your boat from the transducer, the larger/wider the cone angle is the greater the area of coverage. Cone angles vary in difference between each manufacturer, but generally a 200 kHz transducer will have somewhere in between a 12-20 degree cone angle, and a 50 kHz transducer will have anywhere between a 30-40 degree cone angle.

This may be hard to process so try and think of the cone angle as an adjustable torch light, when the light is expanded out it illuminates a wider area than what it would if it was a narrower light beam when adjusted. But when the light source is wider may light up a bigger area but the area isn’t as defined or as lightened as it would if the light beam was narrowed. So what I’m trying to explain is, if the wider the cone angle is selected for example the 83 kHz frequency the more area it will cover and identify fish and structure. But it wont necessarily be as clear. But if the cone angle was say 200 kHz which is a larger beam it wont cover as much area but the sonar beams will be more accurate in returning the image back to the transducer therefore give a more detailed image on your sonar chart screen. I will cover frequency selections in more detail below.

Frequencies

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Sonar Frequencies 200, 83 and 50 kHz

Most sonar units that are sold on the market for general sonar fishing operate a frequency of 200 kHz, some models use 50 kHz and 83 kHz. Some have the capabilities to have a split screen and have 200 kHz on one screen and say 83 or 50 kHz on the other screen so you have a wider cone angle and a narrower angle on the other side to cover both aspects of water coverage. As I have mentioned your typical higher frequencies, like a 200 kHz setting, will excel in showing minute details of the underwater world but will have a smaller area it will cover as opposed to the 83 kHz or 50 kHz frequency, it will have a larger area covered but in less detail.

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In shallower water usually I fish for Bass in the summer months in water up to 20 metres and generally set my frequency on 200 kHz as I’m after a smaller area of coverage cause the water depths are shallower and I’m after more detail because I’m generally looking for that structure that the Bass hide in. If I was fishing a deeper style of fishing like reefs I would set my frequency cone angle to 83 kHz as I’m after that larger cone to cover more area of the waters depths. The 83 kHz frequency setting (or 50 kHz if you don’t have a transducer with 50kHz) has a greater depth penetration for deeper water applications but will return less definition in image quality on the sonar screen.

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Structure Scan Frequencies 455 kHz and 800 kHz

A Structure Scan transducer frequency works nearly exactly the same as a standard sonar frequency using cone angles. A side scan sends the waves outwards and down.  A frequency of a 455 kHz cone angle will be a larger cone and cover a greater area of underwater, but will return back to the sonar chart in less definition. An 800 kHz frequency will send out a smaller cone angle covering less area of coverage but will give a more detailed image displayed on screen.

Structure Scan frequencies are far bigger cone angles than the standard sonar imagery that was explained above. It is created to show 3D images of fish suspending or structure laying in the water column. These frequencies when used with side scanning cause make spotting fish or finding structure of up to 600 feet (183 metres) either side of the boat. Structure Scan is ideal for those anglers that find it critical to find either structure on the banks edge or below the boat in order to find fish hiding or more importantly the habitats fish like to hide in such as fallen trees.

No matter what brand or size sounder you use, take the time to learn yours.

Happy sounding!

Dale Ward

About Dale Ward

Dale Ward grew up in both Sydney and Country Victoria and has fished as far back as he can remember. Dale has found himself casting lures at both freshwater and saltwater species along the East-Coast and prides himself as a new member of the Kaydo Fishing World team.

Previous Kayak Fishing with James in Port Phillip
Next Marlin Time: Trolling Tips For Billfish

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