Furuno 1730 Operator's Manual page 28

shadow sector should be taken. It is a waste of time to attempt the operation in
anything other than very smooth water with little wind.
2) Another method is to observe the shadow sector against a background of sea dutter.
Any shadows will show as dark sectors in the dutter, See Fig.6-13.
Note that a shadow cannot be fairly estimated in heavy dutter, as echoes from either side
of the sector may be spread into it and give an illusion that objects in the sector are being
observed. Nor can it be satisfactorily determined in confined water s, because of the
probability of indirect, false or multiple echoes being produced from nearby buildings or
other vessels.
I
Shadow causecl by mast
Fig.6-13 Appearance of a Shadow Sector on the Display Screen
The result of the above measurement should be recorded on a blind shadow sector
diagram. Fig.6-15 is an example of a shadow sector diagram for the scanner unit sited as
in Fig.6-14. The blind shadow sector diagram should be fixed near the display unit.
Blind Soctoi'
0
°
180°
Fig.6"14 Shadows caused by objects
Fig.6-15 Shadow Sector Diagram
Potentiometer VR801
MD Board
Fig.6-16 Scanner unit
6-15
6-16