America Inc. Fish Finder User Manual

BASIC RADAR THEORY

■ Multiple echoes

Multiple echoes may appear when a short-range and

strong echo is received from a ship, bridge, or break-

water.

Multiple echoes will appear beyond the target’s true

echo point on the same bearing of a large target. They

can be reduced with proper adjustment of the

[SEA]/[ ] control.

See p. 10 for the [SEA]/[ ] control.

True echo

False echoes

Own ship

Another ship

■ Minimum range

Detection at short range is very important. Minimum

range is determined primarily by transmitter pulse

length, vertical beam width and height of the scanner

unit. The shorter the transmission time, the quicker the

return echoes can be received and their distance mea-

sured.

The ability to see targets very close to the ship is de-

creased if the scanner is mounted too high off the

water, because the bottom of the vertical beam of the

scanner cuts off nearby targets.

This target can not be recognized with radar.

The target in this area can not be recognized.

Pulse length

Pulse starting point

Vertical beam width

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