Furuno FELCOM 12 Service Manual page 75

Antenna Power Supply NG
RX+18V/TX+29V, supply voltage to the antenna is divided by R61 and R62 to generate
a monitor signal ANT VOL. The A/D converter (U71) receives the ANT VOL signal and
sends it to the CPU2. If the voltage is not within the rating, "NG" will appear to indicate
short-circuit and/or disconnection. The voltage between J4, #6(+) and J4,#5(-) must be;
RX; 0.91 to 1.01 Vdc
TX; 1.45 to 1.49 Vdc
RX AGC Level NG
CPU 2 (U23) monitors the IF AGC level from the RF CON Board. If the level is less than
80, the receiver circuit in the antenna unit, TX Board, or RF CON Board may be
defective.
1530 - 1545MHz
1530 - 1545MHz
DIPLEXER
ANT
Antenna unit
Communication unit
TX
U25
J6
90.05MHz
RX Lo
(1620.05-1635.05MHz)
RF CON (16P0147)
CPU (16P0148)
6-7
U30,31
U32
Q12
50kHz
U33
AGC AMP
2nd Lo
AGC LEV
(90.1MHz)
AGC LEV
ANT VOL
CPU 2
ANT CUR
(U23) A/D
(U71)
TX LEV
DEMOD
J2-4 50kHz
J2-17
J10-17
J10-4