How Radar Works - Humminbird AS 12RD2KW Installation And Operation Manual

How Radar Works

The word "radar" is an acronym for "Radio Detecting And Ranging." A radio transmitter sends a quick
microwave pulse, and then a receiver listens for that signal's echo when it is bounced back from something
in its path. The returning signal is processed by a computer to determine its relative distance, position, and
bearing. This information is graphically displayed on a view for you to see. Other boats or ships, navigational
markers, and landmasses are referred to as targets.
By knowing how long it takes for a signal to return, the distance to a target can be determined. As the radar
antenna scans through a 360-degree rotation, it can show where the target is relative to your position. By
repeated scans, you can see which direction another boat is moving. How a target is displayed on the screen
depends on the target's height and size as well as its material and shape.
Boat and Surrounding Targets
How radar will perform is mostly determined by the antenna
or scanner. Increasing the size of the antenna improves
long-range performance and target discrimination, or the
ability to distinguish two separate targets at a distance. The
critical factors are the antenna's beam width and side lobe
level. Typically, a radar antenna will radiate a tightly focused
beam from the front of the array. The longer the antenna
array is, the narrower the beam width will be. Additionally,
it will also emit smaller amounts of energy to each side. The
lower the side lobe level, the less the effect of a false echo.
WARNING!
How to interpret the radar display is not included in
this manual. The captain is responsible for the proper use of radar
and the safety of the vessel and its passengers.
1
Radar Display
How Radar Works