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• SCOPE UNIT SYSTEM CLOCK CIRCUIT
The 40 MHz reference signal is amplified at the buffer
amplifier (Q601) via the “40M” line, and then passes
through the low-pass filter (L602, L603, C609–C613). The
filtered signal is applied to the buffer amplifier (SCOPE unit;
Q701) as the 40 MHz system clock via the J601.
3-4 ANTENNA TUNER CIRCUITS
3-4-1 MATCHING CIRCUIT (NETWORK BOARD)
The matching circuit is a T-network. Using 2 tuning motors,
the matching circuit obtains rapid overall tuning speed.
Using relays (RL50, RL60, RL70, RL80, RL90, RL100,
RL110, RL120), the relay control signals from the antenna
tuner CPU (CTRL board; IC1) via the buffer amplifier (IC402)
ground one of the taps of L50, L60, L70, L80, L90, L100,
L110, L120. After selecting the coils, 2 motors (TUNER
unit; MF1, MF2) adjust C1 and C2 using the antenna tuner
CPU (CTRL board; IC1) and the motor controller (CTRL
board; Q3–Q10, D3–D6) to obtain a low SWR (Standing
Wave Ratio).
3-4-2 DETECTOR CIRCUIT (CTRL BOARD)
(1) SWR DETECTOR
Forward and reflected power are picked up by a current
transformer (L101), detected by D101 and D102, and
then amplified at IC101, pin 3 and pin 5, respectively. The
amplified voltages are applied to the antenna tuner CPU
(IC1, pins 2, 3) via “AN0” and “AN1” lines. The tuner CPU
detects the SWR.
(2) REACTANCE COMPONENTS DETECTOR
Reactance components are picked up by comparing the
phases of the RF current and RF voltage. The RF current
is detected by L151 and R151–R154 and buffer-amplified
at IC151, pin 13 and IC154, pin 1 and then applied to the
phase comparator (IC156, pin 1). RF voltages are detected
by C151–C153, C158 and then applied to the phase
comparator (IC156, pin 13) after being amplified at the
buffer amplifiers (IC151, IC153). The output signal from the
phase comparator (IC156, pin 6 for RF current, IC156 pin 7
for RF voltage) is rectified at D154 and D153 for conversion
into DC voltage. The rectified voltage signals are combined,
then amplified at the differential amplifier (IC201, pin 2),
then applied to the antenna tuner CPU (IC1, pin 64) via the
“AN3” line.
A C-MOS IC is used for the buffer amplifier (IC151) to
improve functionable sensitivity; the differential amplifier
(IC201) is very responsive even with a low signal level
input. Together, these ensure quick and stable signal
detection even at low RF signal level input.
(3) RESISTANCE COMPONENTS DETECTOR
Resistance components are picked up by L201, and
detected by D201, D202 and Q201. The detected
resistance components are amplified at the differential
amplifier (IC201, pin 6), and then applied to the antenna
tuner CPU (IC1, pin 1) via the “AN2” line.
3-4-3 MOTOR CONTROL CIRCUIT
(CTRL BOARD AND TUNER UNIT)
The control circuit of the internal antenna tuner consists of
the CPU, EEPROM (Electronically-Erasable Programmable
Read Only Memory), tuning motors and tuning relays.
(1) CPU AND EEPROM (CTRL BOARD)
The antenna tuner CPU (IC1) controls the tuning motors
via the motor controller (Q3–Q10, D3
–D6) and tuning
relays, and memorizes the best preset position in 100 kHz
steps. The memory contents are stored in the EEPROM
(IC2) without a backup battery.
(2) TUNING MOTORS (CTRL BOARD)
A motor controller (Q3–Q10 D3–D6) rotates the tuning
motors (TUNER unit; MF1, MF2) to obtain a low SWR.
(3) TUNING RELAYS (TUNER UNIT)
According to the operating frequency band and antenna
condition, tuning relays select the capacitors and coils.
3-4-4 ANTENNA TUNER CPU PORT ALLOCATION
(CTRL BOARD; IC1)
1
2
13
15
17
21
22, 23
26
27–32
34–40
41–48
64
Input por t for the resistance
components detection voltage.
Input port for the reflected RF
power voltage.
Outputs tuner data signal.
Input port for the serial signal.
Input port for [TUNER] ON/OFF
signal.
Input port for the TX/RX switching
signal.
Input port for the antenna tunner
CPU system clock.
Outputs the coil selection signal.
High :
While 46–60 MHz band is
displayed.
Output the coil selection signal.
Output the capacitor selection
signal.
Output pulse-type control signals
for the tuning motors (MF1, MF2).
Input por t for the reactance
components detection voltage.
AN2
AN1
IKEY
IKEYB
THRU
TRC
#CL1, CL2
VHF
L24M, L18M,
L14M, L10M,
L7M, L3.5M
CO3, CO2,
CO1, CI3,
CI2, CI1
AZ, AY, AX,
AW, PZ, PY,
PX, PW
AN3
Pin
Port
Description
number
name
