Yaesu FT-8800R, Техническое дополнение

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The 50-Watt RF signal is passed through a low-pass filter
network to the antenna switch
D1113 and D1114
( UM9957F ), then passed through a high-pass filter net-
work 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
D1121 and D1122 (both MA2S728 ) then delivered to APC
Q1129 ( NJM2904V ), as a DC voltage which is proportional
to the output level of the power amplifier.
At Q1129 , the rectified DC voltage from the power am-
plifier is compared to the reference voltage from the main
CPU
Q1104 to produce a control voltage, which regulates
the supply voltage to the pre-drive amplifier Q1132
( 2SK2596 ), driver amplifier Q1134 ( RD07MVS1 ), and
power amplifier Q1135 ( RD70HVF1 ), so as to maintain
stable output power under varying antenna loading con-
ditions.
144 MHz
A portion of the power amplifier output is rectified by
D1109 and D1110 (both MA2S728 ) then delivered to APC
Q1129 ( NJM2904V ), as a DC voltage which is proportional
to the output level of the power amplifier.
At Q1129 , the rectified DC voltage from the power am-
plifier is compared to the reference voltage from the main
CPU
Q1104 to produce a control voltage, which regulates
the supply voltage to the pre-drive amplifier Q1132
( 2SK2596 ), driver amplifier Q1134 ( RD07MVS1 ), and
power amplifier Q1135 ( RD70HVF1 ), so as to maintain
stable output power under varying antenna loading con-
ditions.
PTT (Push to Talk) Circuit
430 MHz
When the PTT switch is pressed, pin 8 of sub CPU Q2001
( M38223M4M ) goes “high,” which sends the “PTT” com-
mand to main CPU Q1104 .
When the “PTT” command is received, the main CPU
controls the I/O IC
Q1095 ( BU2090FS ), causing pin 8 of
Q1095 to go “low” which activates the UHF TX switch
section of Q1096 ( IMT17 ).
When the UHF TX switch section of Q1096 is activated, it
controls the antenna switch diodes D1118 , D1119 , and
D1120 (all UM9957F ), modulator switching diode D1088
( DAN222 ), modulator switching transistor Q1114 and
Q1115 (both DTC144EE ), diode switches D1099, D1101,
D1106 and D1107 (all HSC277 ), and APC switches Q1130
( DTA144EE ) and Q1131 ( DTC144EE ), which activate the
430 MHz transmitter circuit.
144 MHz
When the PTT switch is pressed, pin 8 of sub CPU Q2001
( M38223M4M ) goes “high,” which sends the “PTT” com-
mand to main CPU Q1104 .
When the “PTT” command is received, the main CPU
controls the I/O IC
Q1095 ( BU2090FS ), causing pin 9 of
Q1095 to go “low” which activates the VHF TX switch
section of Q1096 ( IMT17 ).
When the VHF TX switch section of Q1096 is activated, it
controls the antenna switch diodes D1113 and D1114
(both UM9957F ), D1117 ( HSC277 ) and D1115, D1116
( RLS135 ), modulator switching transistor Q1114 and
Q1115 (both DTC144EE ), diode switches D1089, D1102,
D1105, D1106 (all HSC277 ) and D1108 ( RLS135 ), and APC
switches Q1130 ( DTA144EE ) and Q1131 ( DTC144EE ),
which activate the 144 MHz transmitter circuit.
PLL Circuit
“Main” band
A portion of the output from UHF-VCO/B Q1116
( 2SC5006 ) is passed through buffer amplifier Q1117
( 2SC5006 ) and diode switch D1086 ( HSC277 ) to the pro-
grammable divider section of the PLL IC Q1109
( MB15A02PFV1 ), where it is divided according to the fre-
quency dividing data associated with the operating fre-
quency input from the main CPU
Q1104 . It is then sent to
the phase comparator.
A portion of the output from the VHF-VCO/B Q1120
( 2SC5374 ) is passed through buffer amplifier Q1121
( 2SC5374 ) and diode switch D1087 ( HSC277 ) to the pro-
grammable divider section of the PLL IC Q1109 , where it
is divided according to the frequency dividing data asso-
ciated with the operating frequency input from the main
CPU
Q1104 . It is then sent to the phase comparator.
The 11.15 MHz reference oscillator X1002 frequency is di-
vided by the reference frequency divider section of Q1109
into 2230 or 1784 parts, to become 5 kHz or 6.25 kHz com-
parative reference frequencies, which are utilized by the
phase comparator.
The phase comparator section of Q1109 compares the
phase between the frequency-divided oscillation frequen-
cy of the VCO circuit and the comparative frequency, and
its output is a pulse corresponding to the phase differ-
ence. This pulse is integrated by the loop filter into a con-
trol voltage (VCV) to control the oscillation frequency of
the VCOs.
Circuit Description