Logic Circuits; 2Nd Lo And Reference Oscillator Circuits; 3Rd Lo Circuit; Band Selection Data - Icom IC-7000 Service Manual

3-3-3 2ND LO AND REFERENCE OSCILLATOR
CIRCUITS (DDS UNIT)
The reference oscillator (X1, Q1) generates a 24.8064 MHz
frequency used for the 1st LO, 3rd LO and DSP circuits as a
system clock and for the 2nd LO signal.
The oscillated signal is multiplied by 5 at Q101 and then
passed through the bandpass filter (FI101). The filtered
124.032 MHz signal is amplified at Q151 and then applied to
the 2nd mixer circuit (MAIN unit) after being passed through
the low-pass filter (L153, C154–C156) and attenuator (R157
–R159) via J151 as the 2nd LO signal.
3-3-4 3RD LO CIRCUIT (DDS UNIT)
The 3rd LO circuit generates a 3rd LO signal and shift the
frequency for the operating mode needed.
The DDS IC (IC51) generates a 10-bit digital signal. The
24.8064 MHz system clock signal from the reference oscil-
lator (X1, Q1) is buffer amplified at IC61 (pins 2, 4) and then
applied to DDS IC (IC51, pins 5, 10). The DDS IC (IC51)
generates the 438.85 kHz frequency signal and then output
from pin 10. The output signal is applied to the low-pass fil-
ter (L53, C59–C61) and then applied to the 3rd mixer circuit
(MAIN unit) via J952 (pin 13) as the 3rd LO signal.
• 3RD LO FREQUENCY
RX frequency
Mode
[kHz]
USB 440.350
LSB 437.350
438.850
CW
(–CW PITCH)
438.850
CW-R
(+CW PITCH)
RTTY 436.555*
RTTY-R 440.975*
AM 438.850
FM 438.850
*RTTY TONE: 2125 Hz, RTTY SHIFT: 170 Hz
TX frequency
[kHz]
440.350
437.350
438.850
438.850
436.555*
436.555*
438.850
438.850
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3-4 LOGIC CIRCUITS

3-4-1 BAND SELECTION DATA

IC2151
(MAIN)
IC2152
Frequency
(MAIN)
[MHz]
HPF
(MAIN)
0.03–1.599999 B0
1.6–1.999999 B1
2.0–3.399999 B2
3.4–3.999999
B3
4.0–6.899999
6.9–7.300000
7.300001–7.999999
B4
8.0–10.999999
11.0–13.899999
13.9–14.350000
14.350001–
B5
14.999999
15.0–20.899999
20.9–21.45
21.450001–
B6
21.999999
22.0–29.999999
T: B1
30.0–49.999999
R: B7
50.0–54.0 B7
54.000001– T: B1
59.999999 R: B7
60.0–115.512999
115.513–
128.999999
L8
129.0-148.0
148.000001–
199.999999
400.0–470.0 L9

3-5 POWER SUPPLY CIRCUITS

3-5-1 FRONT UNIT VOLTAGE LINE
Line
Common 3.3 V converted from the 5 V line
by the 3.3 V regulator circuit (IC151). The out-
3.3 V
put voltage is applied to the sub CPU (IC2003),
etc.
Common 5 V converted from the 8 V line by
the 5 V regulator circuit (IC101). The output
5 V
voltage is applied to the LCD driver (IC506),
etc.
IC2152
(MAIN) IC901
IC981 (DDS)
(PA)
LOF
LPF (PA)
(DDS)
L1
L2
L3
L4
LOF1
L5
L6
L7 LOF2
LOF3
LOF4
L8
LOF5
L9 LOF6
Description