4-1
SECTION 4. CIRCUIT
DESCRIPTION
4-1 RECEIVE CIRCUITS
RF CIRCUITS
The received signal from the antenna connector passed
through the LPF (L90, L94, L96, C409, C418 and C428). The
fi ltered signal is applied to either the VHF or UHF band’s RF
circuit.
VHF BAND (118–174 MHz)
The received VHF band signal from the LPF (L90, L94, L96,
C409, C418 and C428) is passed through the LPF (L79, L83,
L87, C378, C386 and C394) and TX/RX SW (D66, D69 to
D71 and D77), and applied to the PRE-AMP (Q24).
• Left band
The amplifi ed signal is passed through the attenuator (D34)
and tuned BPF (D28, D88, L31, L34, C119, C127, C128 and
C135), and applied to the RF AMP (Q20). The amplifi ed sig-
nal is passed through the tuned BPF (D20, D87, L10, L18,
C60, C71, C74, C79 and C86), and then applied to the 1st
mixer (Q145).
• Right band
The amplifi ed signal is passed through the attenuator (D33)
and tuned BPF (D27, D85, L23, L32, L33, C116, C125, C126
and C132), and applied to RF AMP (Q19). The amplifi ed sig-
nal is passed through the tuned BPF (D19, D86, L9, L17,
C57, C69, C70, C77 and C84), and then applied to the 1st
mixer (Q143).
UHF BAND (375–550 MHz)
The received UHF band signal from the LPF (L90, L94, L96,
C409, C418 and C428) is passed through the HPF (L84, L88,
C392, C395 and C429), TX/RX SW (D68, D73, D75, D84,
L86, L92, C387, C396 and C413), and applied to the PRE-
AMP (Q23).
• Left band
The amplifi ed signal is passed through the attenuator (D32)
and tuned BPF (D22, D24, D26, D30, L21, L28 and L101),
and applied to the RF AMP (Q18). The amplifi ed signal is
passed through the tuned BPF (D12, D16, D91, D92, L4,
L12, L16, L102, C33, C65 and C67), and then applied to the
1st mixer (Q146).
• Right band
The amplifi ed signal is passed through the attenuator (D31)
and tuned BPF (D21, D23, D25, D29, L22, L27 and L99), and
applied to the RF AMP (Q17). The amplifi ed signal is passed
through the tuned BPF (D11, D15, D89, D90, L3, L11, L15,
L100, C32, C63 and C66), and then applied to the 1st mixer
(Q144).
RF CIRCUITS
BPF
HPF
RF
AMP
RF
AMP
ATT
TX/RX
SW
BPF
BPF
BPF
ATT
RF
AMP
LPF
BPF
ANTENNA
BPF
RF
AMP
BPF
LPF
RF
AMP
RF
AMP
ATT
TX/RX
SW
BPF
ATT
LIMITER
LIMITER
118-550MHz
118-174MHz
375-550MHz
118-174MHz
Left band
(VHF)
Right band
(VHF)
Left band
(UHF)
Right band
(UHF)
375-550MHz
400-470MHz
137-174MHz
VHF TX circuit
UHF TX circuit
D68,D73,
D84,D75
D66,D69
D79
D81
Q24
D34
D28,D88
Q20
D20,D87
D33
D27,D85
Q19
D19,D86
Q23
D32
D22,D24,D26,D30
Q18
D12,D16,D91,D92
D31
D21,D23,D25,D29
Q17
D11,D15,D89,D90
D70,D71,D77