Yaesu FT-8900R, Техническое дополнение

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Q1134 (
RD70HVF1
), providing up to 35 Watts of power
output. These three stages of the power amplifier’s gain
are controlled by the APC circuit.
The 35-Watt RF signal is passed through a high-pass filter
network to the antenna switch D1102 , D1104 , and D1146
(all
UM9957F
), then passed through a low-pass filter net-
work and another high-pass filter network to the ANT
jack.
144 MHz Signal
The adjusted speech signal from Q1054 is passed through
the transistor switch Q1051 (
BU4066BCFV
) to varactor
diodes D1076 and D1077 (both
HVC365
), which frequen-
cy modulate the transmitting VCO, made up of VHF-VCO/
B Q1109 (
2SC5374
) and D1078 (
HSC277
).
The modulated transmit signal is passed through buffer
amplifiers Q1100 and Q1111 (both
2SC5374
) and diode
switches D1075 (
HSC277
) and D1128 (
DAN235E
) to the
pre-drive amplifier Q1139 (
2SK2596
).
The amplified transmit signal from Q1139 is passed
through the diode switch D1139 / D1140 (both
HSC277
)
and the driver amplifier Q1137 (
2SK2975
) to diode switch
D1133 (
RLS135
), then finally amplified by power ampli-
fier Q1134 (
RD70HVF1
) up to 50 Watts of power output.
These three stages of the power amplifier’s gain are con-
trolled by the APC circuit.
The 50-Watt RF signal is passed through a low-pass filter
network to the antenna switching relay RL1001 (
G5A-
237P
), then passed through a high-pass filter network and
another low-pass filter network to the ANT jack.
50 MHz Signal
The adjusted speech signal from Q1054 is passed through
transistor switch Q1086 (
BU4066BCFV
) to varactor di-
ode D1093 (
HVC300A
), which frequency modulates the
transmitting VCO, made up of TX50-29-VCO Q1118
(
2SC5374
) and D1094 (
HSC277
).
The modulated transmit signal is passed through buffer
amplifier Q1119 (
2SC5374
) to the pre-Drive amplifier
Q1123 (
2SC5374
).
The amplified transmit signal from Q1123 is passed
through diode switches D1127 (
DAN235E
) and D1141
(
HSC277
) and driver amplifier Q1137 (
2SK2975
) to di-
ode switch D1132 (
D1F20
), then finally amplified by pow-
er amplifier Q1134 (
RD70HVF1
) up to 50 Watts of power
output. These three stages of the power amplifier’s gain
are controlled by the APC circuit.
The 50-Watt RF signal is passed through antenna switch-
ing relay RL1002 (
G5A-237P
) to a low-pass filter network,
then passed through antenna switching relay RL1003
(
G5A-237P
) and another low-pass filter network to the
ANT jack.
28 MHz Signal
The adjusted speech signal from Q1054 is passed through
transistor switch Q1086 (
BU4066BCFV
) to varactor di-
ode D1093 (
HVC300A
), which frequency modulates the
transmitting VCO, made up of TX50-29-VCO Q1118
(
2SC5374
) and D1094 (
HSC277
).
The modulated transmit signal is passed through buffer
amplifier Q1119 (
2SC5374
) to the pre-Drive amplifier
Q1123 (
2SC5374
).
The amplified transmit signal from Q1123 is passed
through diode switches D1127 (
DAN235E
) and D1142
(
HSC277
) and driver amplifier Q1137 (
2SK2975
) to di-
ode switch D1132 (
D1F20
), then finally amplified by pow-
er amplifier Q1134 (
RD70HVF1
) up to 50 Watts of output
power. There three stages of the power amplifier’s gain
are controlled by the APC circuit.
The 50-Watt RF signal is passed through antenna switch-
ing relay RL1002 (
G5A-237P
) to a low-pass filter network,
then passed through antenna switching relay RL1003
(
G5A-237P
) and another low-pass filter network to the
ANT jack.
APC (Automatic Power Control) Circuit
430 MHz
A portion of the power amplifier output is rectified by
D1103 and D1105 (both
MA2S728
) then delivered to APC
Q1130 (
NJM2904V
), as a DC voltage which is proportional
to the output level of the power amplifier.
At
Q1130 , the rectified DC voltage from the power am-
plifier is compared to the reference voltage from the main
CPU Q1084 to produce a control voltage, which regulates
the supply voltage to the pre-drive amplifier Q1139
(
2SK5396
), driver amplifier Q1137 (
2SK2975
), and pow-
er amplifier Q1134 (
RD70HVF1
), so as to maintain stable
output power under varying antenna loading conditions.
144 MHz
A portion of the power amplifier output is rectified by
D1114 and D1115 (both
MA2S728
) then delivered to APC
Q1130 (
NJM2904V
), as a DC voltage which is proportional
to the output level of the power amplifier.
At
Q1130 , the rectified DC voltage from the power am-
plifier is compared to the reference voltage from the main
CPU Q1084 to produce a control voltage, which regulates
the supply voltage to the pre-drive amplifier Q1139
(
2SK5396
), driver amplifier Q1137 (
2SK2975
), and pow-
er amplifier Q1134 (
RD70HVF1
), so as to maintain stable
output power under varying antenna loading conditions.
50 MHz
A portion of the power amplifier output is rectified by
D1119 and D1121 (both
MA2S728
) then delivered to APC
Circuit Description