Circuit Descripiton; Receiver Circuits - Icom IC-PCR1500 Service Manual

SECTION 4
4-1 RECEIVE CIRCUITS
4-1-1RF CIRCUITS (MAIN-A/-B UNITS)
The MAIN-A UNIT has eight RF circuits and one down converter
circuit to provide wide receiving range. The received signals from
the antenna connector (CHASSIS; J1) are applied to RF circuits
or down converter circuit according to the received frequency,
and amplified within the frequency coverage.
IC-PCR2500 contains MAIN-B UNIT which has 4 RF circuits to
provide dulalwatch or diversity capability .
The 0.01–50 MHz signals from the antenna are passed
through the attenuator (D1, D3), band switch (D9) and low-
pass fi lter (LPF; L20, L26, C54, C60, C68, C72, C81, C88),
then applied to one of the RF circuit.
• 0.01–1.8 MHz*
The 0.01–1.8 MHz signals are passed through the band
switch (D29), LPF (L48, L52, C134, C148, C171, C173) and
another band switch (D56), then applied to the 1st mixer
(IC14, pins 4, 5).
<0.01–18 MHz>
D56 D29
LPF From the LPF
• 1.8–15.0 MHz*
The 1.8–15.0 MHz signals are passed through the band
switch (D25), LPF (L43, L47, L50, C102, C120, C125, C131,
C135, C140), high-pass filter (HPF; L57, L60, L72, C150,
C161, C163, C174, C178, C618, C619) and another band
switch (D49), and then applied to the RF amplifier (Q22).
The amplified signals are then applied to the 1st mixer
(IC14, pins 4, 5) via the band switch (D102).
<1.8–15 MHz>
D102 Q22
D49
To the
RF
amp.
1st mixer
(IC14, pins 4, 5)
• 15.0–30 MHz*
The 15.0–30 MHz signals are passed through the band
switch (D82), LPF (L46, L49, C116, C118, C124, C130,
C136), HPF (L55, L58, C139, C149, C151, C162, C164)
and another band switch (D83), and then applied to the RF
amplifi er (Q22). The amplifi ed signals are then applied to the
1st mixer (IC14, pins 4, 5) via the band switch (D102).
<15–30 MHz>
D102 Q22
D83
To the
RF
1st mixer
amp.
(IC14, pins 4, 5)
• 30–50 MHz*
The 30–50 MHz signals are passed through the band switch
(D30), HPF (L77, L82, C201, C206, C208, C213, C216)
and another band switch (D48), and then applied to the RF
amplifi er (Q22). The amplifi ed signals are then applied to the
1st mixer (IC14, pins 4, 5) via the band switch (D102).
<30–50 MHz>
Q22
To the
D102 D48
RF
1st mixer
amp.
(IC14, pins 4, 5)
*MAIN-A UNIT only
CIRCUIT DESCRIPTION
D25
LPF From the LPF
HPF
D82
LPF From the LPF
HPF
D30
HPF
From the LPF
The 50–1300 MHz signals from the antenna are passed
through the anttenuator (D1, D3), band switch (D7) and LPF
(L5, C33, C34), then applied to one of the RF circuit.
• 50–150 MHz
The received signals 50–150 MHz are passed through the
band switch (D5) and the tunable bandpass fi lter (BPF; D8,
D16–D18, D28, D31, L9, L21, L25, L31, L33, C39, C41,
C44, C49, C70), and then applied to the RF amplifi er (Q15).
The amplified signals are passed through another tunable
BPF (D35, D36, L53, L62, L69, L73, C142, C154, C199) and
another band switch (D44), and then applied to the 1st mixer
(IC14, pins 4, 5).
<50–150 MHz>
D35, D36
D44
To the
BPF
1st mixer
(IC14, pins 4, 5)
• 150–350 MHz
The received signals 150–350 MHz are passed through the band
switch (D6) and BPF (D32, L10, L12, L34, L37, L39, C40, C42,
C45, C50, C82, C114, C117), and applied to the RF amplifier
(Q17). The amplified signals are passed through another BPF
(D37, L56, L67, L71, C155, C167, C183, C195) and another band
switch (D46), and then applied to the 1st mixer (IC14, pins 4, 5).
<150–350 MHz>
D37
D46
To the
BPF
1st mixer
(IC14, pins 4, 5)
• 350–700 MHz
The received signals 350–700 MHz are passed through the
band switch (D14) and BPF (D26, D27, L24, L32, L40, C65,
C71, C81, C106), then applied to the RF amplifier (Q16). The
amplifi ed signals are passed through another BPF (D38, D39,
L54, L64, L74, L78, C144, C172, C211) and another band switch
(D47), and then applied to the 1st mixer (IC14, pins 4, 5).
<350–700 MHz>
D38, D39
D47
To the
BPF
1st mixer
(IC14, pins 4, 5)
• 700–1300 MHz
The received signals 700–1300 MHz are passed through the
band switch (D13) and BPF (D19, D23, D33, D34, L22, L27,
L36, L36, L41, L44, C66, C77, C119), then applied to the RF
amplifier (Q18). The amplified signals are passed through
another BPF (D40, D41, L51, L59, L68, L72, C168, C176,
C205) and the band switch (D45), and then applied to the
1st mixer (IC14, pins 4, 5).
<700–1300 MHz>
D40, D41
D45
To the
BPF
1st mixer
(IC14, pins 4, 5)
4 - 1
D8, D16–D18
D28, D31
Q15
D5
RF
BPF From the HPF
amp.
D32
Q17
D6
RF
BPF From the HPF
amp.
D26, D27
Q16
D14
RF
BPF
From the HPF
amp.
D19, D23
Q18
D13
RF
BPF From the HPF
amp.