Kongsberg Simrad SN90 Reference Manual page 477

If the
Horizontal TX Sector
value, the centre of the sector is defined by the
the transmit sector is shown as a triangle originating from the vessel symbol.
SLL is short for sidelobe levels.
The radiation pattern of most antennas shows a pattern of "lobes" at various angles,
directions where the radiated signal strength reaches a maximum, separated by
"nulls", angles at which the radiated signal strength falls to zero. This can be
viewed as the diffraction pattern of the antenna. In a directional antenna in which
the objective is to emit the radio waves in one direction, the lobe in that direction
is designed to have a larger field strength than the others; this is the "main lobe".
The other lobes are called "sidelobes", and usually represent unwanted radiation
in undesired directions.
The power density in the sidelobes is generally much less than that in the main
beam. It is generally desirable to minimize the sidelobe level (SLL), which is
measured in decibels relative to the peak of the main beam. The main lobe and
sidelobes occur for both transmitting and receiving. The concepts of main and
sidelobes, radiation pattern, aperture shapes, and aperture weighting, apply to optics
(another branch of electromagnetics) and in acoustics fields such as loudspeaker
and sonar design, as well as antenna design.
Wikipedia contributors, "Sidelobes," Wikipedia, The Free Encyclopedia,
(https://en.wikipedia.org/wiki/Sidelobes) (Accessed February 2023).
Small sidelobes are generally your best choice. With small sidelobes, the main beam
becomes wider. You achieve small sidelobes when you select a high numerical value.
(Example: ‑30 dB)
The main beam narrows with large sidelobes.
A wide beam is often useful if you are looking for echoes close to the bottom. SLL set
‑
to 17 dB is an average value that works in most cases.
381294/E
value in a horizontal swath is smaller than its maximum
Bearing
Functions and dialog boxes
function. In the Horizontal view
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