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(3) 440 MHz band
The signals from the limiter amplifier (RF unit; IC301)
changes the reactance of a diode (VCO unit; D321) to mod-
ulate the oscillated signal at the 440-VCO circuit (VCO unit;
Q321, Q322, D321, D322, L322). The modulated signals are
amplified at the buffer-amplifier (Q323) and the LO amplifier
(Q823). The amplified signals are applied to the drive/power
amplifier circuits for UHF band.
(4) 1200 MHz band
The signals from the limiter amplifier (RF unit: IC301)
changes the reactance of a diode (VCO unit; D352) to mod-
ulate the oscillated signal at the 1200-VCO circuit (VCO unit;
Q350, D351, D352, L330). The modulated signals are ampli-
fied at the buffer-ampifier (Q351). The amplified signals are
applied to the doubler circuit (Q353), and then passed
through the high-pass (C376–C380, L334, L335) and the
low-pass (C381–C386, L336, L337) filters. The filtered sig-
nals are amplified at the buffer-amplifier (Q354) and the LO
amplifier (Q824). The amplified signals are applied to the
drive/power amplifier circuits for SHF band.
4-2-3 DRIVE/POWER AMPLIFIER CIRCUITS
(RF UNIT)
The amplifier circuit amplifies the VCO oscillating signal to
the output power level.
(1) 50 MHz PA
The signal from the LO amplifiers (Q821) is amplified at the
buffer-amplifier (Q133) and the YGR amplifier (Q134). The
amplified signal is applied to the driver amplifiers (Q921),
and is then amplified at the power amplifier (Q922) to obtain
5.0 W of RF power.
The amplified signal is passed through the antenna switch-
ing circuit (D101 and D102) and low-pass filters, and is then
applied to the antenna connector.
(2) 144 MHz PA
The signal from the LO amplifiers (Q822) is passed through
the Tx/Rx switch (D802 and D803), and is amplified at the
buffer-amplifier (Q133) and the YGR amplifier (Q134). The
amplified signal is applied to the driver amplifiers (Q921),
and is then amplified at the power amplifier (Q922) to obtain
5.0 W of RF power.
• APC CONTROL CIRCUIT
VCC
TXC
+3C
APC SENSOR CIRCUIT
R911
Q912
Q913
430 MHz
RF transmit
signal
50, 144 MHz
RF transmit
signal
D/A CONVERTER
2
3
6 PSET
IC5 (LOGIC unit)
Differential
amplifier
The amplified signal is passed through the antenna switch-
ing circuit (D101 and D102), low-pass filters and high-pass
filters. The signal is applied to the antenna connector.
(3) 440 MHz PA
The signal from the LO amplifiers (Q823) is passed through
the Tx/Rx switch (D804 and D805), and is amplified at the
buffer amplifier (Q135) and the YGR amplifier (Q136). The
amplified signal is applied to the driver amplifier (Q921), and
is then amplified at the power amplifier (Q922) to obtain 5.0
W of RF power.
The amplified signal is passed through the antenna switch-
ing circuit (D402 and D403), low-pass filters and high-pass
filters. The low-pass filtered signal is applied to the antenna
connector.
(4) 1200 MHz PA
The signal from the LO amplifiers (Q824) is passed through
the Tx/Rx switch (D806 and D807), and is amplified at the
buffer-amplifiers (Q131 and Q132) and the YGR amplifier
(Q138). The amplified signal is applied to the driver ampli-
fiers (Q921) to obtain 1.0 W of RF power.
The amplified signal is passed through the antenna switch-
ing circuit (D51 and D52), low-pass filter and high-pass fil-
ters. The high-pass filtered signal is applied to the antenna
connector.
Collector voltages for the drive amplifier (Q921) and control
voltage for the power amplifier (Q922) and YGR amplifier
(Q138) are controlled by the APC circuit to protect the power
module from a mismatched condition as well as to stabilize
the output power.
4-2-4 APC CIRCUITS (RF UNIT)
The APC circuit protects the power amplifier from a mis-
matched output load and stabilizes the output power. The
APC circuit is designed to use VHF, UHF and SHF bands
commonly.
YGR
1200 MHz
amp.
Q138
RF transmit
signal
YGR
amp.
Q135
YGR
amp.
Q134
–
1
VGGC
IC901
+
4 - 4
to the antenna
Drive
Power
amp.
amp.
Q921
Q922
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