Analysis Of Ng Display - Furuno FELCOM 12 Service Manual

Analysis of NG Display

CN/NG
NG appears, even if the equipment is operating normally when the satellite signal is weak.
The CPU1 on the CPU board receives C/N data from the DEMOD circuit. If the signal
level is below 31dB, NG appears, indicating that receiver circuit is defective, ocean
region selection is incorrect, or blocking problem exists.
DIPLEXER
ANT
RF CON
1530 - 1545MHz
Antenna unit
Communication unit
TX
C/N data (8bit)
50kHz
DEMOD
J10-4
CPU
RX
RX
sig.
CPU 1
sig.
(U49)
RX freq.
offset data
VITERBI
(U54)
6-5
To terminal unit
CPU 2
(U23)