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Freeze Frame: Freeze Frame is a Humminbird® feature that pauses the sonar scrolling so that the
image on screen can be studied with greater detail. See Instant Image Update.
Frequency: Frequency is a measure of the number of sound wave cycles per second of a sound
impulse transmitted underwater. A typical frequency for fishfinders is 200 kHz, which offers a
good balance of performance under many conditions. Lower frequencies, such as 50 kHz, are
capable of penetrating to greater depths, but with less resolution. Higher frequencies, such as 455
kHz, offer greater resolution, but are limited in depth performance. Humminbird® uses a variety
of frequencies that are optimized for specific applications.
Grayscale: Grayscale is the use of varying shades of gray to represent the strength of the sonar
signal on the display , and is a very intuitive method of presenting information. Traditionally, the
strongest sonar signals are represented in black, and progressively weaker signals are represented
in progressively lighter shades of gray.
Grayscale, Inverse: Inverse Grayscale is a Humminbird® feature that reverses the correlation of
sonar signal strength and the shade of gray typically used to represent it. The strongest sonar
signals are represented by "white", and progressively weaker signals are represented in
progressively darker shades of gray. While somewhat counter-intuitive, this method makes the
sonar images crisper, and has the benefit 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. A greater number of 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 ability to spot fish and structure over a wide 90° area,
and to identify on which side of the boat they are located. See DualBeam PLUS™.
