( 7 )
VFO UNIT
( PB-1056)
The VFO module board is installed in the VFO chassis.
The VFO uses FET transistors
Ql.
2SK 1 9GR
and
Q2.
2SK 1 9GR
first buffer.
Q3 ,
2SC3 72Y
buffer
provides isolation and amplification of the VFO signal.
The VFO oscillation frequency is
8 700
K Hz
to
9 200
KHz
and covers the tunable I F range of
5 00
K Hz.
Varactor diode
D J ,
1 S2236
in series with capacitor
C14
is switched into the circuit by the clarifier switch
and the relay contacts to shift the V FO freq.uency for
receiver offset tuning.
N o i se Blan ker M o d u l e ( P B- 1 5 8 2 8 )
(8) :\OISE RL.'\ \ K E R l ' \i lT ( PB-1 292)
The
3 1 80
KHz signal i s fe d through
T
1 20
t o
IF
amplifier Q
1 ,
2SC3 72Y,
and then fed through
T
1 2 1 ,
noise blanker gate diode, D
1
and D2 ,
1 S 1 88
FM
and T l 22 to the second
IF
amplifier Q2 ,
2SK 1 9GR.
OUET
ALC
A portion of the input signal to the Noise Blanker
unit is fed through noise amplifier Q
8
,
2SC3 72Y
to a first gate of mixer-oscillator
Q3 ,
3SK40M .
The
AGC voltage controls the gain of the noise amplifier
Q8,
to avoid saturation of Noise Blanker against
an extremely strong noise , Q3 generates 2 7 2 5 KHz
crystal controlled signal which converts
3 1 80
KHz
signal into 45 5 KHz . 4 5 5 KHz signal is amplified
by a noise amplifier Q4 ,
3 SK40M.
The signal passed
through
C20
is rectified by an AGC rectifier
D3,
1 S 1 88
FM ,
and the rectified DC voltage is
amplified by Q5 ,
2SC3 7 2Y
in order to control the
gain of Q4 ,
3 SK40M .
C2 2 is charged by the volt age rectified by D4 ,
1 S 1 88FM ,
however, this voltage does not exceed
the conducting voltage of diode D4 , so that it d oes
not bias the pulse amplifier
Q6, 3SK40M
keeping
Q
6
in conduct with zero bias , in turn , blanker
controller Q7 ,
2SC372Y
stays in non-conducting
state with no noise pulses. As a result , noise gate
diodes D
1 ,
D2 ,
1 S 1 8 8FM
connected in parallel
with Q7 conduct and the signal passes through the
diodes.
When noise pulse exists, the voltage across C22
causes D4 to conduct and Q6 turns int o cutoff, in
turn , Q7 conducts and D l , D2 is biased t o cutoff
preventing the signal passing from the diodes.
(9)
CRYSTAL CONTROL/RF PROCESS OR UN IT
(PB- 1 5 3 4 )
This model is located o n the VFO u nit. The
interconnection of the mod ules is wired directly
without using plug-in socket.
ALC
OUT
I
E
TI
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J
RF
Speech Processor/Crystal Control Circuit Diagram ( PB- 1 534 )
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1 7 -
