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Fish Arch:
A Fish Arch is the apparent "arch" that appears on the display when any
object moves through the sonar cone. The arch results from a gradual decrease in
distance to an object as it moves into the sonar cone. The distance to an object
changes due to the conical shape of the sonar beam, which causes the distance to be
greater at the edges of the beam than at the center of the beam. When this distance
change is graphed on the display, an arch appears.
Fish ID+™:
Fish ID+™ is a Humminbird® feature that uses advanced sonar processing
algorithms to determine if a detected object is likely to be a fish. When the sonar
signal from an object meets strict parameters, the unit draws a Fish Symbol (or icon)
and the digital depth of the target. On DualBeam and DualBeam PLUS™ units, fish
detected in the narrow center beam are shown as shaded symbols, and fish detected
in the wider beam are shown as hollow symbols.
Fish Symbol:
A Fish Symbol is the graphic that is displayed on the screen when Fish
ID+ determines that a sonar return is likely to be a fish. See
Fish ID+
.
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.
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