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The detected signal output from the PLL IC (pin 2) is
converted into a DC voltage (lock voltage) at the loop filter
and then fed back to one of the VCO circuits (Q5521,
D5521, L5523).
The oscillated signal from the buffer amplifier (Q5601) is
also applied to the MAIN unit via the "M1LO" line as a 1st
LO signal after being amplified at LO (Q5602) and buffer
(Q5603) amplifiers or passed through the bandpass filter
(L5602–L5604, C5610–C5616).
4-3-3 2ND LO AND REFERENCE OSCILLATOR
CIRCUITS (PLL UNIT)
The reference oscillator (X5251) generates a 32.0 MHz
frequency for the DDS circuits as a system clock and
for the LO output. The oscillated signal is doubled at the
doubler circuit (Q5202) and the 64.0 MHz frequency is
picked up at the double tuned filter (L5203, L5204). The
64.0 MHz signal is applied to the RF circuit via the "M2LO"
line as a 2nd LO signal.
4-3-3 3RD LO CIRCUIT (PLL UNIT)
The DDS IC (IC5701) generates a 10-bit digital signal using
the 32 MHz system clock. The digital signal is converted
into an analog wave signal at the D/A converter (R5701–
R5720). The converted analog wave is passed through the
low-pass filter (L5781–L5783, C5781–C5785) and is then
applied to the MAIN unit as the 3rd LO signal (422.500
kHz) via the attenuator (R5781–R5783).
• PLL CIRCUIT
PLL IC (IC5401)
Phase
detector
Programmable
Programmable
divider
divider
DDS IC
(IC5101)
Phase
Programmable
detector
divider
Programmable
divider
D/A
convertor
MAIN loop VCO
Loop filter
Q5521,
D5521,
Q5604
L5523
LO
Loop filter
Reference loop VCO
Q5301, D5301
AMP.
Q5351
DDS
Reference OSC. (32 MHz)
X5251; [USA], [CAN]
X5281; [OTH]
4-4 FRONT UNIT (RC-26)
4-4-1 LCD CIRCUIT (DISPLAY AND CONNECT
BOARDS)
The LCD (CONNECT board; DS8920) is controlled by the
LCD driver (CONNECT board; IC8940) via the drive signals
(CL1, RES, CS, RS, WR, RD, DB0–DB7) from the display
board. The LCD's back light employs 5 LEDs (DS8300–
DS8304). The LEDs are controlled by dimmer (Q8300,
Q8303) and dimmer controller (IC8280) circuits.
4-4-2 MICROPHONE CIRCUIT (DISPLAY BOARD)
The AF signals from the microphone are amplified at the
AF amplifier (IC8280) via the "MIC" signal. The signals are
applied to the IC-F7000's main unit through the J2501, pin
1 via the "FMOD" line.
4-4-3 KEY'S BACK LIGHTS CIRCUIT (DISPLAY
BOARD)
The key"s back lights compose of DS8305, DS8306,
DS8308, DS8309, DS8311–DS8314, and are controlled
by the dimmer (Q8301) and dimmer controller (IC8280)
circuits. The dimmer circuit is controlled by the FRONT
CPU.
4-4-4 RESET CIRCUIT (DISPLAY BOARD)
The reset IC (IC8202) resets the FRONT CPU (IC8201)
when IC-F7000 is power ON or OFF.
Q5601
Q5602
Buff
LO
Q5202
Doubler
Q5302
Buff
DDS
IC5701
4 - 6
Q5603
1st LO
Buff
(64 94 MHz)
2nd LO
(64 MHz)
3rd LO
D/A
(443 kHz)
convertor
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