Furuno FAR-1513-BB Operator's Manual page 99

Shadow sectors
Funnels, stacks, masts, or derricks in the path of the antenna block the radar beam. If
the angle subtended at the antenna is more than a few degrees, a non-detecting sec-
tor may be produced. Within this sector targets can not be detected.
Wharf and its echo
Radar position
Large ship
Radar position
Shadow sector
occurs because
wharf is hidden
behind ship.
Size of blind sector depends
on size of obstruction and range.
2. RADAR OBSERVATION
Wharf and its echo
Shadow sector occurs
because obstruction
(like mast) is in path
of radar beam.
2-5