Furuno FAR-1416, Operator'S Manual

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1. OPERATIONAL OVERVIEW
1-37
1.30 How to Reject Second-trace Echoes
In certain situations, echoes from very distant targets can appear as false echoes
(second-trace echoes) on the screen. This occurs when the return echo is received
one transmission cycle later, or after the next radar pulse has been transmitted.
This equipment lengthens the pulse repetition period to reject false echoes.
Note: This function decreases the number of echo hits. Use this function carefully so
that the possibility of detecting small targets and high-speed craft does not lessen.
To reject second trace echoes, do the following:
1. Open the [MAIN MENU].
2. Select [ECHO], then press the
left button .
3. Select [2ND ECHO REJ], then press the left button .
4. Select [ON], then press the left button . Select [OFF] to disable rejection.
5. Close the menu.
1.31 How to Measure Range
The range to a target can be measured three ways: with the fixed range rings, with the
cursor, or with the VRM.
Use the fixed range rings to get an estimate of the range to a target. The rings are the
concentric solid circles on the display. The number of rings is automatically set by the
current range scale. The distance between the rings is the range ring interval, and the
current interval appears at the upper-left position on the screen. To measure the range
to a target with the range rings, count the number of rings between the center of the
display and the target. Check the range ring interval and estimate the distance of the
echo from the inner edge of the nearest ring.
Pulse
interval
Actual ranges
Second-trace
echo
Measured ranges