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Ci rcu i t Descr i ption
the 12.8-MHz crystal reference, after buffering
by Q2009 (2SC4116GR), by 2560 (or 2048) to
produce the 5-kHz (or 6.25-kHz) loop refer
ence (respectively).
The 5-kHz (or 6.25-kHz) signal from the
programmable divider (derived from the
VCO) and that derived from the reference os
cillator are applied to the phase detector sec
tion of Q2005, which produces a dual 5-V
pulsed output with pulse duration depending
on the phase difference between the input sig
nals. This pulse train is filtered to DC and
returned to varactors D201 /D202 on the 430
VCO Unit.
Changes in the level of the DC voltage ap
plied to the varactors affect the reactance in the
tank circuit of the VCO, changing the oscillat
ing frequency of the VCO according to the
phase difference between the signals derived
from the VCO and the crystal reference oscil
lator. The VCO is thus phase-locked to the
crystal reference oscillator.
The output of VCO Q201 is also buffered by
Q202 and delivered to the 430 Mother Unit for
a mplification by Q2002 before application to
the 1st mixer, as described previously.
For UHF transmission, VCO Q201 oscillates
between 430 and 450 MHz according to the
m odel version and programmed transmit fre
quency. The remainder of the PLL circuitry
s hared with the receiver. However, the divid
ing data from the microprocessor is such that
the VCO frequency is at the actual transmit
frequency (rather than offset for IFs, as in the
receiving case) . Also, for transmission, the
VCO is modulated by the filtered speech audio
a pplied to the tank circuit at D203, as de
s cribed previously. Receive and transmit 5-V
buses select which VCO is to be active by Q204
and Q205 (both DTC144EE), respectively. PET
Q2007 (2SK880GR) on the 430 Mother Unit
buffers the VCV line for application to the
tracking band-pass filters in the receiver front
end.
When the power saving feature is active,
the microprocessor periodically signals the
PLL IC to conserve power and shorten lock-up
time.
Spurious Emissions
Spurious emissions from the 144 & 430
Mother Units radiating through the outer en
closure are reduced by die-cast aluminum
shielding. By-pass capacitors are also utilized
on the external EAR & MIC connectors .
Power-On Sequencing
Pressing the orange
volts to CPUS pin 24 of microprocessor Q1005
to wake it up. This pulls the NRS line high via
Q1801 (28811320) on the Key Unit, which
provides 5 volts to the 144 and 430 Switch
Units, which in turn provide regulated voltage
to the other boards.
Battery Charger
jack J2004 on the 430 Mother Unit
EXT DC
applies voltage to the B+ line through diode
D2030 to operate the transceiver, and through
is
regulator Q2017 (2SB1132Q) to the charging
terminal of the battery. The outer (negative)
contact of the
EXT DC
ative side of the battery from direct chassis
ground connection, placing diode D2024 in
line instead when a plug is inserted in the jack.
switch applies 5
POWER
Power Control
&
jack disconnects the neg
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