Appendix; Performance Monitor - Furuno FAR-2805 Series Operator's Manual

A.1 Performance Monitor
For X-band radars, the FURUNO PM-30
satisfies the reguirement covering
9410 50 MHz. For S-band radars, the
PM-50 is available covering 3050 30
MHz.
The performance monitor is an indepen-
dent 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 com-
pletely a separate device.
Operating the performance
monitor
When Radar Interswitch RJ-7 is con-
nected, set it to the "straight" mode. Press
the PM ON/OFF button at the lower left
corner in the Turning Compartment, and
the range scale is automatically set to 24
nm range scale, producing the monitor
display. The radar screen will show sev-
eral 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 trans-
mitter and receiver are in good working
conditions in as much as the original state
when the monitor was turned up, the in-
nermost 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. The receiver sensitivity can be
evaluated from the number of visible arcs;
one arc is lost every 3 dB deterioration of
the sensitivity.

APPENDIX

Transmitter
performance
Range to Loss
innermost
arc
12 nm 0 dB
9 nm 3 dB
6 nm 6 dB
3 nm or 10 dB
less or none
Display Meaning
TRANSMITTER: normal
RECEIVER: normal
12 nm
TRANSMITTER: 3 db loss
(Transmitter system has lost
half of initial power.
Suspect magnetron and
9 nm
feeder system.)
RECEIVER: normal
TRANSMITTER: 3 db loss
(Transmitter system has lost
half of initial power.
Suspect magnetron and
9 nm
feeder system.)
RECEIVER: 3 db loss
(Receiver has lost half of
normal sensitivity. Suspect
receiver front end, water
leakage in feeder system,
etc.
Receiver
performance
No. of Loss
arcs
4 0 dB
3 3 dB
2 6 dB
1 9 dB
0 12 dB
A-1