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of enhancing the apparent sensitivity because the weaker signals appear bolder.
Inverse grayscale works well in very clear water. Debris-laden water often appears as
a lot of clutter on the screen.
Instant Image Update: Instant Image Update is a Humminbird® feature that
updates all the sonar information on the display when Sensitivity and a variety of
sonar settings (Bottom View, Range, etc.) are modified. This differs from the
traditional functionality that only updates the new sonar information collected after
the setting change. Instant Image Update permits more accurate fine-tuning of the
display because the user can see the results on the complete sonar graph. When
combined with the Freeze Frame feature, the user can adjust and understand the
effects of many different sonar settings quickly and easily.
Maximum Depth Menu: The Maximum Depth Menu is a Humminbird® feature that
optimizes performance based on the maximum operational depth set by the user.
Many Humminbird® units can operate across a very broad depth range (up to 2500
feet) which causes the unit to "look" up to that full depth under some circumstances.
Due to the speed of sound in water, this can result in less responsiveness because
the unit has to wait for a longer period of time to receive the sonar signal. When the
Maximum Depth menu is set to a lower value, the unit only looks up to the setting,
which increases the responsiveness of the unit. This is an important feature for
anyone operating in shallower depths!
Noise: Noise is unintentional, external sound waves that interfere with the optimal
operation of sonar. Noise appears as random "dots" on the display, and is caused by
a variety of sources. Electrical noise (from trolling motors, bilge pumps, VHF radios)
typically manifests as a consistent dot pattern. Electrical noise can be isolated by
selectively turning on and off other electrical devices to determine the source. Often
re-routing the power cable, or connecting to an alternative power supply (second
battery) can help overcome electrical noise. Hydrodynamic noise (from propeller
and/or hull cavitation) has a more random appearance and is generally related to
boat speed, so that faster operation results in more noise. Hydrodynamic noise can
be overcome by proper transducer installation. Many Humminbird® products have a
Noise Filter menu setting that allows the user to clear the screen of noise that is
difficult to eliminate.
Pixels: Pixels are the "picture elements", or small square blocks, that make up the
image on the LCD. Measured as a vertical by horizontal number (i.e. 640V x 320H),
this key specification typically indicates the quality of resolution. In fishfinders, the
total resolution (vertical multiplied by horizontal) is often less important than the
"Vertical Pixel" resolution. See Pixels, Vertical.
Pixels, Vertical: Vertical Pixels are a number of vertical picture elements in a single
column on an LCD display. More vertical pixels provide finer resolution of targets
detected by sonar. Essentially, a vertical distance (the depth), when divided by a
larger number, breaks that distance into smaller samples, each representing a
smaller area and thus providing more detail. In fishfinders, vertical pixels are more
critical than horizontal pixels because the horizontal axis of the display represents
time, or history. Sonar information on the horizontal axis can vary greatly,
depending on boat speed and the Chart Speed setting. A greater number of
horizontal pixels show more sonar history that the boat has passed through. On
many models, Humminbird® provides the most vertical pixels to provide a better
display resolution. See Chart Speed and Pixels.
Power Output: Power output is the amount of sound energy emitted into the water
by the sonar transmitter. Power output is measured using either RMS (Root Mean
Square) or P-T-P (Peak-to-Peak) measurement systems. Either method is acceptable,
but it is important, when comparing power outputs, to make sure that the same
measurement system is being used for both outputs, because P-T-P numbers are 8
times higher than RMS numbers. Greater power output allows the sonar signal to
penetrate through weeds and thermoclines, reach deeper depths and operate more
effectively in noisy environments, such as when the boat is running at high speed.
Pulse Width (Pulse Length): Pulse Width is the length of time that a sonar sound
burst is transmitted into the water. Shorter pulse widths provide better target
separation, but cannot travel to great depths. Longer pulse widths provide better
depth penetration, but result in poorer target separation. Humminbird® varies pulse
width based on depth to optimize both target separation and depth performance.
See Target Separation.
QuadraBeam™: QuadraBeam™ is a Humminbird® sonar configuration that uses four
sonar beams for a more detailed bottom image. QuadraBeam™ uses the DualBeam
PLUS™ configuration for downlooking, and also adds two additional beams to look
to the left and right. The sonar beams pointing to the left and right provide the
