Humminbird

Tri-Beam
For the widest coverage, the Tri-Beam uses three sonar beams to form a continuous 90 degree area of uninterrupted coverage and reaches a depth of 600-1000 feet depending on the fish finder unit. A precise center beam locates fish and detailed bottom structure, while two wide beams look to the left and right to cover an area TWICE your depth - in 20 feet of water, the wide beams cover an area 40 foot wide. The tri-beam ID+ fish identification display fish in the center beam as solid, fish in the wide beams as hollow and point left or right indicating location.

Wide Side
The Wide Side uses three sonar beams to keep an eye on bank and bottom structure. A center sonar beam shoots down to 120 feet while port and starboard signals spread out 120 feet in either direction.

Six Beam
Six separate beams provide excellent contour and shape for on-screen 3D display clearly depicting bottom structure and drop-offs. The six beams provide 53 degrees of continuous coverage up to 240 feet deep.

How Sonar Works
All fish finder `s operate using Sonar. Developed during World War II, this technology uses sound waves to "view" underwater objects. A sound wave is produced by the fish finder and sent through the water. At the source, the wave is narrow; however as it penetrates deeper, the sound wave spreads forming a cone, or what is commonly called a beam (think flashlight). When the sound wave encounters something within this beam, it bounces back to the fish finder . By measuring the very small amount of time between when the sound wave was send out and when it bounces back your fish finder calculates the distance and draws it on the screen.

If the signal doesn't encounter anything along the way, it reaches the bottom. Soft bottoms like mud and weeds tend to absorb the signal. Hard bottoms such as rock reflect a stronger signal back. These subtle differences in sonar reflections appear on the display screen. That's how a fish finder "reads" the bottom and everything in between.

Cone Angles
The cone angle is the angular measurement of the sonar beam in degrees. For instance, a 24 degree beam is broader and covers more area than 16 degree beam. Cone angles are measured at "-10db", which is a method to assure consistency of measurement from one transducer to another, and accurately represent the capability of the fish finder .

That cone angle varies by fish finder model and manufacturer. Many fish finder `s use only one sonar beam; however Humminbird has advanced multi-beam sonar technology that sends out, 2, 3 or even 6 sonar beams to cover much wider area with much greater detail than ordinary fish finder `s.

Fish Targets
Fish targets are displayed as either the unprocessed sonar return called an "arch", or as a Fish ID symbol. You can choose either presentation.

To display Fish ID symbols, a Humminbird fish finder 's use sophisticated software to analyze the "shape" of the sonar return from a suspended target to determine whether it is a fish . When a fish is detected it is displayed as graphic fish symbols on your viewing screen. If you have a multiple beam configuration, Fish ID provides the added benefit of identifying the location of the fish : either, to the left, right or directly below your boat.

To display "arches", the fish finder relies on the characteristics of sonar. When a fish passes directly through the transducer's beam, it can form an arch on the display screen. The size of the fish arch is affected by the sensitivity setting of the unit, your boat speed, the depth of the water and the location of the fish within the sonar beam. Often only partial arches will be displayed because the fish does not travel directly through the center of the beam.

Water Clarity
The water's clarity also has a great deal to do with the integrity of the signal. Strong winds or currents can create bubbles in the water that disperse the signal. Suspended mineral particles or floating algae, plankton or other microorganisms could absorb sound rather than reflect it back. Wave action can also stir things up - the greater the chop, the more air gets into the equation.

Thermoclines
Some fish finder 's also show thermoclines, which are the "fronts" where warmer waters intersect with cooler waters. Typically, the water is colder as you go deeper and certain fish prefer certain temperatures. The change in water temperature causes some of the sonar signal to reflect back creating a line across your screen at the depth of the thermocline. Identifying thermoclines brings you one step closer to catching the fish you're after.

The Transducer
The transducer takes the electrical signal from your transmitter, turns it into sonar, and sends it out. It also captures all returning echoes and converts them back into electrical signals. Transducers are mounted in the water, either on the transom, the inside the hull, or on the trolling motor. All transducers should be mounted straight down and away as far from motors, props and hull obstructions as possible. A cable connects the transducer to the fish finder .

The LCD Display Screen
The LCD displays the sonar information and is the one of the most important aspects of the fish finder . LCD displays are measured in "pixels" - the little square blocks on the screen that make up the image. More pixels provide better resolution and a clearer picture. FSTN displays, standard on all Humminbird products, offer the best visibility from any location on the boat, and provide high contrast for easy reading. FSTN displays are easy to identify because the pixels are black, not blue. Grayscale technology offers even more detail by showing the sonar image in multiple shades of gray; this makes it easy to clearly distinguish bottom type, structure and fish .

Information from humminbird.com

Humminbird Depth Finder - Humminbird Depth Finder