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Descr i ption
The FT-530 electronics consists of three ma
jor boards: the 144 and 430 (MHz) mother
boards (or Mother Units) and the Control Unit,
and numerous minor boards that mount on
these. The motherboards include the receiver
front ends, IF and PLL subsystem ICs, and
support daughter boards for transmit stages,
local VCOs, supply regulation and switching
circuits. The Control Unit includes the micro
processors and tone generator
I
decoder chips,
and supports daughter boards for the display,
keys and keypad, audio circuits and an inter
face board for coupling with the mother
boards. While reading this description, you
can ref er to the block diagram for an overview
of the major circuit blocks, and to the sche
matic diagrams for component details.
Antenna Duplexer
Incoming
RF
from the antenna jack passes
through a 450-MHz low-pass filter on the 430
Mother Unit before application to two band
switching networks: coil L2009, diode D2003
and capacitor C2033 on the 430 Mother Unit,
a
_
nd D501 on the 430 PA Unit for UHF signals;
and coil L3006, diode D3003 and capacitor
C3029 on the 144 Mother Unit, and D901 on
the 144 PA Unit for VHF signals. These net
works filter VHF signals from the UHF re
ceiver and UHF signals from the VHF receiver,
allowing each band to operate independently
while sharing the same antenna connection.
VHF Reception
VHF signals passed by the duplexer are ap
plied to a varactor-tuned band-pass filter con
sisting of T3004 and D3016/D3017 before
RF
amplification by Q3016
(2SC4537).
The am
plified
RF
is then band-pass filtered again by
varactor-tuned resonators T3003 /D3020 /
D3023, T3002/D3019/D3022 and T3001/
D3018 /D3021 to ensure pure in-band input to
1st mixer Q3011
(2SK882Y).
Tuning voltage
for the varactors is provided by VHF PLL
Q3005, buffered by Q3007
(2SK880GR).
Buffered 128.75 - 138.75-MHz output from
the VCO Unit is amplified by Q3002
(2SC-
4245)
and applied to the 1st mixer. The result
ing 15.25-MHz 1st mixer product is passed
through dual monolithic crystal filters XF-
3001/XF3002
(±
7.5-kHz BW) to strip away all
but the desired signal, which is then amplified
by Q3012
(2SC4215Y)
before delivery to FM
IF subsystem IC Q3010
(MC3372D),
contain
ing the 2nd mixer, 2nd local oscillator, limiter
amplifier, noise amplifier, S-meter amplifier
and squelch gates. A 2nd local signal is gener
ated from 15.705-MHz crystal X3001, which
produces the 455-kHz 2nd IF when mixed
with the 1st IF signal within Q3010. The 2nd IF
.
is passed through ceramic filter CF8001 on the
IF Unit daughter board to strip away unwan
ted mixer products, and is then applied to the
limiter amp in Q3010, which removes ampli
tude variations in the 455-kHz IF before detec
tion of the speech by ceramic discriminator
CD8001, also on the daughter board.
Detected audio from pin 9 of Q3010 is de
emphasized and passed to detector output
gates Q8001 and Q8002
(2SC4116G R
x
2) and
gate controller Q8003
(DTC144EE)
on the 144
IF Unit. If the squelch is open, the signal is then
delivered via the 144 Mother Unit, Interface
Unit and Control Unit (for sampling by CTCSS
&
DTMF detectors), and then to the MIC/
AF
Amp Unit.
VHF Squelch Control
When no carrier is received, noise at the
output of the detector stage in Q3010 is ampli
fied and band-pass filtered by the noise amp
section of Q3010 and the network between
pins 9 and 10, and then rectified by D3013. The
resulting DC squelch control voltage, adjusted
by the
SOL
control on the VOL Unit, is passed
to the squelch switching section within Q3010.
While no carrier is received, pin 14 of Q3010
(the Scan Stop line) remains low, signaling pin
9 of microprocessor Q1006
(HD4074808H)
on
the Control Unit to keep the green (Busy) half
of the VHF
ON AIR/BUSY
LED off, and holding
the AF MUTE line to the MIC AF Amp Unit
high to block VHF receiver audio from passing
through analog gate Q1406 while no signal is
being received, and during transmission.
When a carrier appears at the discriminator,
noise is removed from the output, causing pin
14 of Q3010 to go high and signaling micro
processor Q1006 to activate the
BUSY
LED. The
microprocessor then checks CTCSS chip
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