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Transducers Explained

Fishfinders use transducers like an antenna. All fishfinders need a transducer to work. Marine electronics like marine radar and marine VHF radios use antennas in the air. A marine fishfinder has an underwater antenna called a transducer. Actually the word transducer refers to a device that transforms physical energy into electrical energy, so a microphone or a temperature sensor are also transducers. For this discussion, we refer to the sonar transducer. Fishfinders send a pulse of energy out of the transducer and then listen for an echo. The transducer is usually in the water. Transducers have two ratings , frequency and power.

Frequency is how fast the transducer vibrates. It’s like a radio station’s channel. You must chose a transducer that matches the frequency of your fishfinder. Some fishfinders operate on more than one frequency.

Power is the maximum power that the transducer can handle. A 1000 watt fishfinder needs a 1000 watt or larger transducer. A 600 watt fishfinder can use a 1000 watt transducer, but if you try a 1000 watt fishfinder into a 600 watt transducer, it will probably damage the transducer.

Transducers come in many sizes and shapes. The three types are Through Hull, Transom Mount and In-Hull. Generally, through Thru Hulls are for inboards, Transom Mount are for outboards and stern drives and In Hulls are for go fast boats.

A transducer generates a huge pulse of enregy which travels to the bottom and is reflected back. The transducer is also used to listen for the tiny reflected pulse. This process is actually quite sensitive, so a transducer is affected by many environmental factors. The biggest problem is turbulence.

When a boat moves, the water rushing under the hull creates a great deal of turbulence. A small cavitation bubble moving across the face of a transducer will immediately cause the fishfinder to lose the bottom. So it is important that the physical mounting minimizes bubbles. Placing the transducer deep in the water helps a lot.

For inboard boats, the best place is down toward the keel in the middle third of the boat. Keep in mind the travel lift slings, you don’t want to lift the boat on the transducer. The deadrise of the hull is corrected using a fairing block or a tilted element transducer. Most fishing boats use a through hull triducer, with speed and sea water temperature. Most sailboats use two, a through hull depth and a through hull speed / temperature transducer. Most outboards and stern drive boats use a transom mount triducer with speed and temperature. If you are unsure of which transducer to use, call 847-746-0100 and TMS Technical Marine Support will send you the correct one guaranteed.

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