4 - 1
• RF CIRCUITS
SECTION 4
CIRCUIT DESCRIPTION
4-1 RECEIVE CIRCUITS
RF CIRCUITS
VHF BAND (108–174 MHz)
The RF signal from the antenna is passed through two LPFs
(L513, L515, L516, C547, C549, C553, C555 and C556),
ANT SW (D506, D903) and BPF (L705, L706, L909, C724
and C976), and then applied to the RF AMP (Q702).
• Band A (137–174 MHz)
The amplifi ed signal is passed through the BPF (D705, L703
and C715) and AGC circuit (Q49, Q50, D34, D704), and then
applied to the RF AMP (Q701).
The amplifi ed signal is applied to the 1st IF circuit, through
the BPF (D702, D703, L701, C703 to C705).
• Band B (108–174 MHz)
The amplifi ed signal is passed through the ATT (D745), BPF
(D744, L742 and C753) and AGC circuit (Q903, D743), and
then applied to the RF AMP (Q740).
The amplifi ed signal is applied to the 1st IF circuit, through
the BPF (D741, D742, L740, C741 to C743).
D506,D903
RX:380.000M~479.000MHz
D501
D508
D510
RX:108.000M~174.000MHz
TX:400.000M~479.000MHz
TX:136.000M~174.000MHz
D503,D504
From the TX circuit
From the TX circuit
Q702
D705D702,D703
Q740
-Band A:137M-174MHz-
-Band B:108M-174MHz-
D744
Q701
D741,D742
-Band A:380M~479MHz-
Q601
Q602
D605,D606
-Band B:380M~479MHz-
Q641
108M-174MHz
380M-479MHz
D602,D603
D642,D643 D645,D646
AGC
AGC
AGC
AGC
Q49,Q50,D34
Q903,D743
Q49,Q50,D34
Q903,D644
D704
D604
D745
To the 1st IF circuit (Band A).
To the 1st IF circuit (Band B).
To the 1st IF circuit (Band B).
To the 1st IF circuit (Band A).
ANT
SW
HPF
LPF
LPF LPF
ANT
SW
LPF
BPF
BPF
RF
AMP
BPF
BPF
RF
AMP
RF
AMP
RF
AMP
RF
AMP
BPF
RF
AMP
BPFBPF
BPF
ATT
UHF BAND (380–479 MHz)
The RF signal from the antenna is passed through the HPF
(L512, L514, C545, C548, C550, C551 and C554), two LPFs
(L511, C536, C539 and L507, C524, C526, C529), ANT SW
(D508 and D510) and BPF (L608, L610, L612, C630, C631
and C634), and then applied to the RF AMP (Q602).
• Band A
The amplifi ed signal is passed through the two BPFs (D605,
L605, C615 and D606, L606, C619) and AGC circuit (Q49,
Q50, D34, D604), and then applied to the RF AMP (Q601).
The amplifi ed signal is applied to the 1st IF circuit, through the
BPF (D602, D603, L602, L603, C603 to C605, C607, C907).
• Band B
The amplifi ed signal is passed through the BPF (D645, D646,
L644, L645, C654, C655, C658) and AGC circuit (Q903,
D644), and then applied to the RF AMP (Q641).
The amplifi ed signal is applied to the 1st IF circuit, through
the BPF (D642, D643. L641, L642, C642 to C644, C646 and
C972).
To Next Page
Loading...
Need help?
General
