Simrad MN000802A-G manual Yacht installations, How to find the optimum height for the scanner

4.3 Yacht installations

Normally you should install the scanner horizontally, to produce an equal sweep around the yacht. However, a yacht heels over to the lee side, and when the heel angle exceeds 50% of the vertical beam width of the radar, this can cause two problems:

•on the windward side of the yacht, the beam is projected too high to sweep the water surface effectively. Targets can be missed completely or appear at very poor resolution on the display unit.

•on the lee side of the yacht, the beam is projected too low and is concentrated over a small area of water so that sea clutter becomes a problem on the display unit.

In this case, you're recommended to install the scanner on a gimbal mounting so that it can operate effectively in a heavy swell or when the yacht is heeled over.

4.4 How to find the optimum height for the scanner

The optimum height for the scanner is as close as possible to the A-B line for best performance. How to find the A-B Line:

The vertical extent of the radar beam is 2θ°, so most of the radar beam is concentrated within this angle, meaning that outside of this angle the radar beam will be very weak.

Scanner model	θ° value (half the -3 dB beam
	width)
2 kW	15
4 kW	12.5
6 kW	10
10 kW	10
25 kW	10

An example of an A-B Line is shown in the picture. If you install the scanner below the A-B line, the scanner will be too low. It will be difficult to acquire distant targets and the superstructure will be more likely to impede the passage of the beam and generate false echoes. If the scanner is installed too high above the A-B line, the beam will miss close targets and increase sea clutter return.