Garmin AQUAMAP 10x2 Series Owner's Manual page 56

Off Low
Interference Setting
Interference from other acoustic equipment operating nearby or other
electronic equipment on your boat may appear on the display as shown
in the figures below. You may reduce the effect with a noise limiter.
There are varying degrees of interference. Minor interference or noise
can be stray signals that can look like actual targets. Severe noise can
completely fill the screen and make depth readings impossible. To counter
interference, you have to first identify the type of interference. Although
most noises can be eliminated with fairly simple techniques, some
interferences can only be reduced to a more acceptable level.
Sonar Cross-Talk interference: caused by nearby sonar of similar
transmit frequency. It will appear as the diagonal lines across the screen.
When two sonar's transducer cones intersect, the units will not be able to
tell the signals apart. See figure (A) below.
Electromagnetic Interference (EMI): caused by powerful electromagnetic
waves radiated from electric equipment and wirings. The electromagnetic
waves are then absorbed by the transducer cable and appear as vertical
lines on the screen. See figure (B) below.
46
Medium High
(A) Interference from other sonar
Color Limit: Hides part of the color palette to help eliminate fields of weak
clutter.
By setting the color limit to the color of the undesired returns, you can
eliminate the display of undesired returns on the screen.
Smoothing: Removes noise that is not part of a normal sonar return, and
adjusts the appearance of returns, such as the bottom.
When smoothing is set to high, more of the low-level noise remains
than when using the interference control, but the noise is more subdued
because of averaging. Smoothing can remove speckle from the bottom.
Smoothing and interference work well together to eliminate low-
level noise. You can adjust the interference and smoothing settings
incrementally to remove undesirable noise from the display.
Surface Noise: Hides surface noise to help reduce clutter. Wider beam
widths (lower frequencies) can show more targets, but can generate more
surface noise.
TVG: The TVG (Time Variable Gain) compensates for propagation loss
(B) Electrical interference
Surface noise
AQUAMAP™ 10x2/12x2 SERIES