Fish Finders and Sonar

The electronics are about as important as the boat itself for the avid angler.  There is a bewildering array of electronics brands, sonar units, feature sets and transducers.  The electronics manufacturers all have proprietary names for key features such as: Traditional, Clearvu, Sidevu, Panoptics, Livescope, CHIRP, RealVision 3D, Sidevision, Downvision, Sidescan, Downscan, Activetarget, Fish Reveal, etc. 

To get full functionality of the fish finder/sonar unit, the transducer which transmits and receives the sonar signal, must have matching capabilities to work properly.  There is a so many options it is easy to get lost and confused.  Garmin has over 25 different transducers for various functions and capabilities.

• Garmin
• Raymarine
• Lowrance
• Furuno
• Si-Tex
• Simrad
• Humminbird

Type of Transducers

Transom Mount

• • Pros
    • Any type of hull
    • Simple installation
    • The most common type of transducer
  • Cons
    • Does not work for inboards or sailboats
    • Can be sensitive to location and placement near the motor

In-hull

• Pros
  • Does not require a hole in the hull
  • Doesn’t collect marine growth or debris
  • Great high speed performance
• Cons
  • Not available for wood, metal or similar hull materials
  • Not as clear or powerful as other types due to signal loss through the hull
  • Limited depth capability

Trolling motor

• Pros
  • Provides an image from the bow which could be better for locating fish
  • Does not require a hole in the hull
  • Simple installation and removal
• Cons
  • Can be damaged in shallow water.

Thru-hull

• Pros
  • Better images at higher boat speeds
  • Minimal marine growth and debris
• Cons
  • Typically, professionally installed as it requires a hole to be drilled through the hull
  • Advanced units require a larger hole in the boat

Transducer Features

Power and Frequency

The more power in the transducer the better it can read deeper bottom structure and images.  Power typically is rated from 200 watts to 2000 watts with the high power ratings required reading deeper water.  Sonar units can read deeper depths in freshwater than in saltwater with the same hardware.

The lower the transducer frequency (measured in kHz) the deeper you can read and image but with lower resolution and the higher frequencies have better resolution with lower depth capability.

The sonar vendors list their depth and frequency capabilities for the various transducer and sonar unit combinations.  If you have questions it is best to call their support lines for clarification as there are various options and models change frequently.

Traditional Imaging

All sonar units and transducers support traditional imaging technology.  Traditional imaging can be best for locating fish in the water column and a basic image of the bottom structure.  It is best to combine traditional imaging with CHIRP to get the best overall view of the water.

CHIRP Imaging

For the avid angler, a CHIRP transducer and sonar unit is a must.  CHIRP is an acronym that stands for Compressed High Intensity Rapid Pulse.  CHIRP functionality provides a sweep of frequency signals in the water (rather than a single frequency with traditional) and supplies a detailed image to the fish finder unit.  Certain bottom structure shows up better at certain frequencies and will give a much better image when using CHIRP rather than traditional sonar.   

Airmar is the manufacturer of OEM transducers for major sonar vendors.  They have some great, detailed information and presentations about CHIRP technology here.

Low frequency CHIRP is best for reading higher depths and structure up to 10,000 feet.  Medium frequency CHIRP is best for mid to shallow level water – typically under 500 feet.  High frequency CHIRP is best for the most detail on more shallow depths and targets.

SUMMARY

A great sonar unit is critical for the avid angler to maximize their fishing success.  The matching of the sonar/transducer to their specific fishing scenario is important for the best results.    From my research, some manufacturer demos of advanced features while very compelling to look at are much better in the demo vs. real world usage, especially in saltwater.

My boat came from the manufacturer with a basic, traditional transducer and I upgraded to a second transducer that supports CHIRP and SIDE/DOWN imaging for my purposes.  The higher end sonar units support multiple transducers so the angler can get the best image quality regardless of the water conditions.

If you have any questions or are considering a boat purchase, contact me by email at [email protected].

Tight lines …  Capt. P.

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