Receiver Circuits - Icom IC-7100 Service Manual Addendum

SECTION 3.

3-1 RECEIVER CIRCUITS

RF CIRCUIT (PA UNIT)
• While operating on the HF, 50 MHz and 70 MHz bands
The RX signal from the antenna connector ([ANT1]: J1) is
passed through the power/SWR detect circuit (D961 and
D962) and one of the LPFs, depending on the operating
band, to remove unwanted out-of-band signals. (See the LPF
TABLE below.)
The fi ltered RX signal is passed through the TX/RX SW
(RL801) and LPF (L801, L802, C801, C803 and C805) for fur-
ther removal of unwanted signals, and then passed through
the mute SWs (D181 and D182).
When the attenuator is turned ON, the RX signal is passed
through the 18 dB attenuator (MAIN UNIT: D3082 and D3083).
• RF CIRCUITS
f c=500MHz D3272
LPF BRF
To the 1st RX IF circuit
(74.8MHz or above)
Q3201
PRE
AMP
fc=74.8MHz
LPF
To the 1st RX IF circuit
(74.8MHz and below)
• LPF TABLE
Operating frequency
Filter
(MHz)
L1 0.030000 to 1.999999 RL880 RL881 L881, L882 C882 to C886, C888 to C890, C893, C894, C896, C897, C899
L2 2.000000 to 3.999999 RL920 RL921 L921, L922, C922 to C929, C933, C984
L3 4.000000 to 7.300000 RL840 RL841 L841 to L843, C842 to C848, C850, C854 to C859
L4 7.300001 to 14.350000 RL900 RL901 L901 to L903, C902, C907
L5 14.350001 to 21.450000 RL940 RL941 L942, L943, C944 to C947, C950, C953
L6 21.450001 to 32.999999 RL820 RL821 L822, L823, C824 to C828, C833, C835
L7 33.000000 to 74.799999 RL860 RL861 L861 to L863, C863 to C866, C868, C869, C873, C875 to C878
CIRCUIT DESCRIPTION
D181,D182
74.8MHz or above
74.8MHz and below
18dB D3072
ATT MUT E
0.03-1.6MHz
LPF
"B1"
1.6-74.8MHz
1.6-2.0MHz HPF
"B2"
2.0-3.4MHz
HPF
"B3"
3.4-6.9MHz
HPF
"B4"
6.9-13.9MHz
HPF
"B5"
13.9-20.9MHz
HPF
"B6"
20.9-40.0MHz
HPF
"B7"
40.0-60.0MHz
BPF
"B8"
60.0-74.8MHz
HPF
"B9"
Filter switches
The RF signal is passed through one of the BPFs, depend-
ing on the operating frequency, to remove unwanted signals.
(See the BPF TABLE on page 3-2.)
The fi ltered signal is applied to the pre-AMP circuit.
PRE-AMP CIRCUIT (MAIN UNIT)
When the pre-AMP is turned ON, the RX signal is amplifi ed
by the pre-AMP (Q3201).
The amplifi ed signal is applied to the 1st RX IF circuits.
From the TX circuit
TX/RX
SW
fc=74.8MHz
LPF
MUTE
D422,423,424
From the
TX/RX
TX circuit
SW
From the
TX/RX
TX circuit
SW
Q481
RF
BPF
AM P
BPF
Components
3-1
0.03-2.0MHz
LPF
"L1"
2.0-4.0MHz
LPF
"L2"
4.0-7.3MHz
LPF
"L3"
7.3-14.35MHz
LPF
"L4"
14.35-21.45MHz
LPF
"L5"
21.45-33.0MHz
LPF
"L6"
33.0-74.8MHz
LPF
"L7"
430 MHz band
(400-470 MHz)
D433,D434
fc=270M fc=700M
HPF LPF
MUT E
fc=200M
LPF
144 MHz band
(74.8-200 MHz)
20dB
Q451
430 MHz
PRE
BPF ATT
AM P
(400-470MHz)
20dB
Q551
144 MHz
PRE
BPF ATT
AM P
(74.8-200MHz)
HF/50MHz/70MHz
ANTENNA
D961,D962
PWR/SWR
DET
PA UNIT
144/430MHz
ANTENNA
D651,D661
PWR/SW R
DET
Control line
(Active High)
L1
L2
L3
L4
L5
L6
L7