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3 - 2
(2) 50–60 MHz (BPF AND RXPLL-A UNITS)
When [P.AMP] switch is set to [P.AMP 1] or [P.AMP 2],
the amplified signals from the DW amplifier (BPF unit;
Q901) are applied to the pre-amplifier2 (BPF unit; Q903)
or pre-amplifier1 (RXPLL-A unit; Q1209, Q1210) via the
P.AMP2_ON selectors (BPF unit; RL902, RL903) and
P.AMP1_ON selectors (RXPLL-A unit; RL1203, RL1206),
respectively. Pre-amplified or bypassed signals are applied
to the 1st mixer circuit after being passed through the low-
pass filter (RXPLL-A unit; L1217–L1219, C1244–C1250,
C1268).
• RX-B CIRCUIT
(1) 0.03–30 MHz (RXPLL-B UNIT)
The RF signals from the DIGISEL unit are applied to (or
bypass) the DW amplifier (Q1001) via the DW selectors
(RL1001, RL1002), and are then applied to the pre-
amplifier circuit.
When [P.AMP] switch is set to [P.AMP 1] or [P.AMP 2], the
signals are applied to the pre-amplifier1 (Q1007, Q1008) or
pre-amplifier2 (Q1006) circuit via the P.AMP_ON selectors
(RL1003, RL1006) and P.AMP selectors (RL1004, RL1005),
respectively. Pre-amplified or bypassed signals are applied
to the 1st mixer circuit after being passed through the low-
pass filter (L1052–L1054, C1053–C1057, C1067).
(2) 50–60 MHz (BPF AND RXPLL-B UNITS)
When [P.AMP] switch is set to [P.AMP 1] or [P.AMP 2],
the amplified signals from the DW amplifier (BPF unit;
Q961) are applied to the pre-amplifier2 (BPF unit; Q953)
or pre-amplifier1 (RXPLL-B unit; Q1209, Q1210) via the
P.AMP2_ON selectors (BPF unit; RL952, RL953) and
P.AMP1_ON selectors (RXPLL-B unit; RL1203, RL1206),
respectively. Pre-amplified or bypassed signals are applied
to the 1st mixer circuit after being passed through the low-
pass filter (RXPLL-B unit; L1217–L1219, C1244–C1250,
C1268).
3-1-4 1ST MIXER CIRCUIT
(RXPLL-A AND RXPLL-B UNITS)
The 1st mixer circuit mixes the receive signals with the 1st
LO signal to convert the receive signal frequencies into
a 64.455 MHz (main) or 64.555 MHz (sub) 1st IF signal.
The IC-7800 has four 1st mixer circuits for the dualwatch
function.
• RX-A OR RX-ONLY CIRCUITS (RXPLL-A UNIT)
(1) 0.03–30 MHz
The filtered signals pass through the L1055, and are
then applied to the 1st mixer circuit (IC1051). The applied
signals are mixed with 1st LO signal from the RXPLL-A
circuit to convert into a fixed 64.455 MHz 1st IF signal.
The converted 1st IF signal is applied to the 50/HF selector
(IC1081, pin 1).
(2) 50–60 MHz
The filtered signals pass through the L1220, and are then
applied to the 1st mixer circuit (Q1211, Q1212). The applied
signals are mixed with 1st LO signal from the RXPLL-A
circuit to convert into a fixed 64.455 MHz 1st IF signal.
The converted 1st IF signal is applied to the 50/HF selector
(IC1081, pin 3).
The selected 1st IF signal passes through the low-pass
filter (L1058, L1060, L1062, L1063, C1061, C1062, C1064,
C1066, C1070, C1074, R1054), and is then applied to the
1st IF circuit.
• RX-B CIRCUIT (RXPLL-B UNIT)
(1) 0.03–30 MHz
The filtered signals pass through the L1055, and are
then applied to the 1st mixer circuit (IC1051). The applied
signals are mixed with 1st LO signal from the RXPLL-B
circuit to convert into a fixed 64.555 MHz 1st IF signal.
The converted 1st IF signal is applied to the 50/HF selector
(IC1081, pin 1).
(2) 50–60 MHz
The filtered signals pass through the L1220, and are then
applied to the 1st mixer circuit (Q1211, Q1212). The applied
signals are mixed with 1st LO signal from the RXPLL-B
circuit to into a fixed 64.555 MHz 1st IF signal.
The converted 1st IF signal is applied to the 50/HF selector
(IC1081, pin 3).
The selected 1st IF signal passes through the low-pass
filter (L1058, L1060, L1062, L1063, C1061, C1062, C1064,
C1066, C1070, C1074, R1054), and is then applied to the
1st IF circuit.
1st LO Main
1st LO Sub
Crystal
filter
FI401,
FI402,
FI403
FI401,
FI402,
FI403
Main 1st mixer
IC1051,
Q1211, Q1212
Sub 1st mixer
IC1051,
Q1211, Q1212
2nd LO Main
PWR amp.
IC140
Main 2nd mixer
IC1051,
IC1052
Sub 2nd mixer
IC1051,
IC1052
2nd LO Sub
Crystal
filter
0.03 60.0 MHz
0.03 60.0 MHz
DSP-A
board
MAIN unit
CHASSIS
unit
DSP-B
board
RXPLL-B UNIT
RXPLL-A UNIT
• RECEIVER CONSTRUCTION