Yaesu FT-530, Technical Supplement

Page: 16 / 122

C i rcuit
the 430 Mother Unit, before delivery to the
antenna.
VHF Automatic Transmit Power Control (APC)
RF power output from the VHF final ampli­
fier is sampled and rectified by D3004 (188-
321). The resulting DC is fed back through
Q801 (28811320) and Q802 (28C4617) on
the APC Unit to driver Q3002 (28C4245) on
the 144 Mother Unit, controlling the level of
drive to the PA module, and thus the power
output. The microprocessor selects either high
or one of three low power levels via Q804
(UM81 ).
When the VHF transmitter PLL is unlocked,
or while receiving, the INH line ·causes the
ULTS line to be dropped via Q808 (OTC144-
EE), Q806 (UMW1) and Q807 (28811320),
which disables transmission by biasing final
amplifier Q901 off and opening VHF t/r
switch D901.
VHF Transmit/Receive Switching
Closing the PTT switch on the Key Unit
pulls one side of the microphone low, which
turns on Q140S (28A 1586Y) on the Mic/
AF
Amp Unit, putting S volts on PTT pin 33 of
microprocessor Ql OOS on the Control Unit.
The microprocessor then delivers appropriate
serial data to shift register Q1201 (TC4094BF)
on the Interface Unit to raise the TX line to the
144 Switch Unit (via the 144 Mother Unit)
where Q703 (OTA123YE) turns off the receiver
RS line, and Q704 (UM02) and Q701 (OTA-
143XE) turn on the transmitter TS line. This TS
signal is delivered to the 144 APC Unit where
it causes the ULTS line to go high via Q806 and
Q807, which in turn biases the VHF PAmodule
on and closes t/r switch D901 on the 144 PA
Unit. At the same time, Q801 on the 144 APC
Unit turns on Q3002 on the 144 Mother Unit to
drive the PA module.
Late UHF Transmit Stages
On the 430 VCO Unit, the modulated signal
from UHF VCO Q201 (28C4226) is buffered
by Q202 (28C4226) and returned to the 430
Mother Unit for amplification by Q2002 (28C-
4227), and then final amplification by UHF PA
module QSOl (8-AU26) on the 430 PA Unit.
The transmit signal then passes through an­
tenna t/r switch D501 before returning to the
duplexer network and the 3-pole low-pass fil­
ter consisting of L2001�3, C2014, C2018,
C2007, C2022�23, C20131�32 and C2037
mounted on the 430 Mother Unit before deliv­
ery to the antenna.
UHF Automatic Transmit Power Control (APC)
RF
power output from the UHF final ampli­
fier is sampled and rectified by D2004 (188-
321 ). The resulting DC is fed back through
Q401 (28811320) and Q402 (28C4617) on
the 430 APC Unit to driver Q2002 (2SC4227)
. on the 430 Mother Unit, controlling the level of
drive to the PA module, and thus the power
output. The microprocessor selects either high
or one of three low power levels via Q404
(UM81 ).
When the UHF PLL is unlocked, or while
receiving, the INH: line causes the ULTS line to
be dropped via Q408 (OTC144EE), Q406
(UMW1) and Q407 (28811320), which dis­
ables the transmitter by biasing final amplifier
QSOl off and opening UHF t/r switch DSOl.
UHF Transmit/Receive Switching
As for VHF, closing the PTT line raises the
TX line via Q140S on the Mic/ AF Amp Unit,
Q1005 on the Control Unit and Q1201 on the
Interface Unit. This line connects to the 430
Switch Unit (via the 430 Mother Unit) where
Q303 (OTA 123YE) turns off the receiver RS
line, and Q304 (UM02) and Q301 (OTA143XE)
turn on the transmitter TS line. This TS signal
is delivered to the 430 APC Unit where it
causes the ULT5 line to go high via Q406 and
Q407, which in turn biases the UHF PA mod­
ule on and closes t/r switch D501 on the 430
PA Unit. At the same time, Q401 on the 430
APC Unit turns on Q2002 on the 430 Mother
Unit to drive the PA module.
VHF PLL Frequency Synthesizer
The VHF PLL circuitry consists of separate
receive and transmit VCOs Q601 and Q602,
and VCO buffer Q603 (all 2SC4226) on the 144
VCO Unit; PLL subsystem IC Q300S (MB87-
091 PF-G-BNO) on the 144 Mother Unit, and
12.8-MHz reference oscillator X2001/Q2009
on the 430 Mother Unit. Q3005 contains a pres­
caler, reference divider, serial-to-parallel data
latch, programmable divider, phase compara­
tor, charge pump and a power saver circuit.
\
)