Lowrance Transducer Information

Choosing a Transducer

Choosing a transducer is the most important part of designing your sonar system. The transducer is the mechanism that creates the sonar image, so the characteristics of a transducer greatly affect the performance of the sounder. With so many different technologies, transducer selection can get tricky. The main points to consider are:

  • How will it be mounted?
    • Most inland water boats are fitted with a transom or a shoot-thru hull Broadband transducer as well as a second Broadband transducer on the bottom of the trolling motor. In addition to a transom mounted StructureScan transducer
    • Most bay/flats/offshore boats are fitted with a transom mount or a thru-hull transducer
  • What views do I want?
    • Broadband and CHIRP can be accomplished with the same transducer- the difference is in the sonar module attached
    • StructureScan requires a different style of transducer
    • SpotlightScan requires another transducer different than the other two
  • What frequencies do I need?
    • It is easy to be confused by the available frequencies a quick breakdown is:
      • Low CHIRP or 50kHz—Lower frequency means higher power for offshore fishing
      • Medium CHIRP or 83kHz—Specially designed to give the widest coverage area, 83 kHz is great for watching a bait under the transducer in shallow water
      • High CHIRP or 200kHz—Higher frequencies display a higher resolution image making it easy to discern fish from structure or structure from the bottom
      • 455kHz—Built into StructureScan and SpotlightScan 455kHz allows for scanning of large distances with your SideScan or SpotlightScan
      • 800kHz—Also built into StructureScan and SpotlightScan 800kHz yields less range but higher resolution detail than 455kHz 

Most boaters will decide to choose two different sonar technologies, Broadband and StructureScan HD. This means that in many cases there are two different transducers needed one for Broadband or CHIRP and a second for StructureScan. 

Sonar Technology


CHIRP sonar is the cutting edge echosounder technology. Unlike the single frequency limitations of Broadband sonar, CHIRP continuously sweeps a spectrum of frequencies. Sweeping frequencies makes two improvements to the sonar image. First it cancels out errant noise that would have been picked up by a single frequency sonar. Second, it allows us to put more power into the water by sending and receiving echoes at different frequencies. This means fish that relate to each other, underwater structure or the bottom become easier to differentiate from the structure they are holding to. Lowrance has changed the way we use CHIRP technology by enabling the ability to use transducers that were not initially designed for CHIRP sonar in certain frequency ranges.


Single frequency sonar- also referred to as Broadband Sonar is commonly annotated as 50kHz, 83kHz, or 200kHz. Broadband is the essential sonar technology at its finest. Broadband sonar relies on pings and echoes from a single frequency. This technology is great for tracking bottom, finding schools of baitfish, displaying predator fish, and bait tracking.


StructureScan allows users to scan an area with a very high frequency signal, producing picture-like images. 455 and 800kHz frequency selections allow users to choose between 455 for scanning great distances, and 800 for close-in high resolution detail. SideScan turns the sonar paradigm on its side with the ability to search to the left and right of your boat rather than only below. SideScan imagery can be displayed on top of the chart page for a detailed view of structure in relation to your position, called StructureMap. StructureMap is excellent for finding underwater structure and changes in bottom layout.


SpotlightScan is angler controlled directional sonar—this gives anglers with a cable steer trolling motor the ability to aim two sonar signals similar to StructureScan in a specific direction. Anglers can now scan an area they are interested in fishing while on approach. When fishing drop-offs, channels, and underwater structure anglers can now highlight productive fish-holding spots before positioning their boat over top of them. This means finding and casting to fish is easier than ever.