SECTION 4
CIRCUIT DESCRIPTION
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).
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).
4 - 1
<0.01–18 MHz>
D29
LPF
From the LPF
D56
• 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>
LPF
HPF
From the LPF
To the
1st mixer
(IC14, pins 4, 5)
D25
D49
D102 Q22
RF
amp.
• 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>
From the LPF
To the
1st mixer
(IC14, pins 4, 5)
LPF
HPF
D82
D83
D102 Q22
RF
amp.
• 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>
From the LPF
To the
1st mixer
(IC14, pins 4, 5)
HPF
D30
D48
Q22
RF
amp.
D102
<50–150 MHz>
D8, D16–D18
D28, D31
BPF
D35, D36
BPF
From the HPF
To the
1st mixer
(IC14, pins 4, 5)
D5
Q15
RF
amp.
D44
• 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>
D32
BPF
D37
BPF
From the HPF
To the
1st mixer
(IC14, pins 4, 5)
D6
Q17
RF
amp.
D46
• 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>
D26, D27
BPF
D38, D39
BPF
From the HPF
To the
1st mixer
(IC14, pins 4, 5)
D14
Q16
RF
amp.
D47
• 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>
D19, D23
BPF
D40, D41
BPF
From the HPF
To the
1st mixer
(IC14, pins 4, 5)
D13
Q18
RF
amp.
D45
*MAIN-A UNIT only
