9
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
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