Interference Rejector; How To Measure The Range To A Target; How To Turn Range Rings On/Off - Furuno FCR-2107 Operator's Manual

2.10

Interference Rejector

Mutual radar interference may occur in the vicinity of another
shipborne radar operating in the same frequency band as own radar. It is
seen on the screen as a number of bright spikes either in irregular
patterns or in the form of usually curved spoke-like dotted lines
extending from the center to the edge of the picture. Activating the
interference rejector circuit can reduce this type of interference.
The interference rejector is a kind of signal correlation circuit. It
compares the received signals over successive transmissions and
suppresses randomly occurring signals. There are three levels of
interference rejection depending on the number of transmissions that
are correlated.
1. Use the trackball to select the IR indication at the left side of the
screen.
2. Push the left button to select the interference rejection level
desired. The indication changes in the sequence of OFF, 1, 2, and
3. The higher the value the greater the rejection.
2.11

How to Measure the Range to a Target

The range to a target may be measured three ways: with the fixed range rings, with the cursor, or with the VRM.
Use the fixed range rings to obtain a rough estimate of the range to a target. They are the concentric solid circles
about own ship, or the sweep origin. The number of rings is automatically determined by the selected range scale
and their interval is displayed at the upper-left position of the screen. Count the number of rings between the center
of the display and the target. Check the range ring interval and judge the distance of the echo from the inner edge of
the nearest ring.
2.11.1

How to turn range rings on/off

1. Use the trackball to select the MENU box at the right side of the screen.
2. Push the left button to display the Main menu.
3. Spin the scrollwheel to select Mark then push the scrollwheel.
4. Use the trackball to place the arrow on the setting of Range Rings.
5. Spin the scrollwheel to select OFF or ON as appropriate then push the scrollwheel.
6. Click the Close window button (X) to close the Mark menu.
15. Navigation Sensors
Interference
rejector
2-15