Power Supply Line - Yaesu FT-8900R Technical Supplement

is divided according to the frequency dividing data asso-
ciated with the operating frequency input from the main
CPU Q1084. It is then sent to the phase comparator.
A portion of the output from the TX50-29-VCO Q1118
(2SC5374) is passed through buffer amplifier Q1119
(2SC5374) and diode switch D1096 (HSC277) to the pro-
grammable divider section of the PLL IC Q1095, where it
is divided according to the frequency dividing data asso-
ciated with the operating frequency input from the main
CPU Q1084. It is then sent to the phase comparator.
A portion of the output from the RX50-29-VCO Q1121
(2SC5374) is passed through buffer amplifier Q1122
(2SC5374) and diode switch D1096 to the programmable
divider section of the PLL IC Q1095, where it is divided
according to the frequency dividing data associated with
the operating frequency input from the main CPU Q1084.
It is then sent to the phase comparator.
The 11.15 MHz reference oscillator X1003 frequency is
divided by the reference frequency divider section of
Q1095 into 2230 or 1784 parts, to become 5 kHz or 6.25
kHz comparative reference frequencies, which are utilized
by the phase comparator.
The phase comparator section of Q1095 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 charge pump consist-
ing of D1067 (UDZS5.1B), Q1098 (2SA1774), Q1099
(2SC4617), and loop filter into a control voltage (VCV) to
control the oscillation frequency of the VCOs.
Circuit Description
"Right" band
A portion of the output from the UHF-VCO/B Q1106
(2SC5006) is passed through buffer amplifier Q1107
(2SC5006) and diode switch D1079 (HSC277) to the pro-
grammable divider section of the PLL IC Q1090
(MB15A02PFV1), where it is divided according to the fre-
quency dividing data associated with the operating fre-
quency input from the main CPU Q1084. It is then sent to
the phase comparator.
A portion of the output from the VHF-VCO/B Q1109
(2SC5374) is passed through buffer amplifier Q1110
(2SC5374) and diode switch D1080 (HSC277) to the pro-
grammable divider section of the PLL IC Q1090, where it
is divided according to the frequency dividing data asso-
ciated with the operating frequency input from the main
CPU Q1084. It is then sent to the phase comparator.
The 11.70 MHz reference oscillator X1002 frequency is
divided by the reference frequency divider section of
Q1090 into 2340 or 1872 parts to become 5 kHz or 6.25
kHz comparative reference frequencies, which are utilized
by the phase comparator.
The phase comparator section of Q1090 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 charge pump consist-
ing of D1061 (UDZS5.1B), Q1091 (2SA1774), Q1092
(2SC4617), and loop filter into a control voltage (VCV) to
control the oscillation frequency of the VCOs.

Power Supply Line

When the user presses and holds in the "Left" VOL knob
for 2 seconds, pin 23 of the main CPU Q1084 goes "low"
and pin 39 of main CPU Q1084 goes "high," which acti-
vates the power switch Q1057 (2SB1301), Q1061
(2SC4617), and Q1062 (2SA1774), to supply 13.8 VDC to
each circuit in the transceiver.
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