Furuno FR-2105-B - Manual (Page 146)

-8.1-
Chapter 8 ANCILLARY EQUPMENT
8.1 Performance Monitor
A performance monitor is required for a radar installed on vessels of 300 GT and upward
engaged in international voyages. For X-band radars, the FURUNO PM-30 or PM-50 satisfies
the requirement covering 9410 ± 50 MHz. For S-band radars, the PM-50 is available covering
3050 ± 30 MHz. The following describes how to use these performance monitors.
The performance monitor is an independent unit, namely, it is not interconnected with any unit
of the radar system except for the 100 VAC power cable. In some radars the power cable is not
routed via the power switch or other control of the radar and the monitor is operated as
completely a separate device.
Operating the performance monitor
When Radar Interswitch RJ-7 is connected, set it to the "straight" mode. Press the PM ON/OFF
button in the Turning Compartment, and the range scale is automatically set to 24 nm. The radar
screen will show several arcs, opposite to the heading marker (provided that the performance
monitor is installed behind the radar antenna as is normally the case). If the radar transmitter and
receiver are in good working conditions in as much as the original state when the monitor was
turned up, the innermost are should appear at 12 nm and there should be a total of 4 arcs.
The range of the innermost arc reduces 3 nm with every 3 dB loss of transmitted power.
Meanwhile the receiver sensitivity can be evaluated from the number of visible arcs; one arc is
lost every 3 dB deterioration of the sensitivity.
Transmitter performance Receiver performance
Range to innermost arc Loss Number of arcs Loss
12 nm 0 dB 4 0 dB
9 nm 3 dB 3 3 dB
6 nm 6 dB 2 6 dB
3 nm or less or none > 10 dB 1 > 9 dB
0 > 12 dB