( 4 ) A U D IO UNIT
( P B 1 3 1 5 A )
This module contains the m icrophone ampl i fier. receiver
audio ampl i fier. VOX ampl i fier and CW sidetone oscil
lator. A speech signal from the m icrophone is fed to
the first MIC ampl i fier
Q l . 2SK 1 9GR
FET
from pin 5 .
Input im pedance o f the MIC ampl i fier i s 5 0
K
ohms.
The signal. control led i n ampl itude by the MIC GAIN
control between pin 3 and pin 4 . is ampli fied by the
second m icropbone ampl i fier Q2.
2SC3 72Y
and appl ied
to the em itter fol lower
Q
3 .
2SC3 72Y
to be del ivered
to the modu lator unit from pin 8.
The re c e ive r aud i o s ignal f r o m the A U D I O G A I N
c o n t r o l i s a pp l i ed th rough p i n 1 9 to a p r e a mp l i f i e r
Q9,
2SC 1 000,
and ampl ified by integrated c i rcuit Q8,
AN2 1 4 .
Th i s s tage, in tu r n , inc r e a s e s the s ignal to
s peake r l eve l . The aud i o powe r ampl i f i e r c i r c u i t
u t i l i z e s the O T L ( output t rans fo rme r l e s s ) c i r c u i t
and delivers 3 watts output t o t h e speaker through
p i n
22.
The signal from the first m icrophone ampl i fier is coupled
through the VOX GA IN control potentiometer
VRl
to
VOX ampl i fier
Q 4 . TA7042M .
The signal ampl i fied
by
Q4
is fed to the VOX rectifier. The positive DC
output voltage of the recti fier is appl ied to the gate
of the VOX relay control transistors
Q5 . 2SK 1 9Y
and
Q6. 2SC3 73
causing them to conduct and actuate
the VOX relay
RLl
on the main chassis. The collector
circuit of
Q6
is connected to RU through pin 1 3 .
The ANTITRIP circu it provides a threshold voltage
to prevent the speaker output from tripping the trans-
ceiver into the transm it function.
The receiver audio
Q ,
Q ,
Q ,
Q ,
Audio Module ( PB- 1 3 1 5 )
V R5 to the antitrip ampl i fier
Q4 .
and fed to rectifiers
DI
and 02.
l S l S S S .
Negative DC output voltage from
the recti fier. conn ected to the gate of
Q5 .
red uces the
gain of the VOX control transistor prov iding the neces
sary antitrip threshold. A NTITRIP control V R5 adjusts
the value of the antitrip voltage threshold so that the
loud speaker output will not produce excessive positive
DC output from the VOX rect ifier to exceed the nega
tive DC outpu t from the antitrip recti fier and cause
the control transistor to actuate the relay . When speak
ing into the m icrophone nornnl ly the positi\'e voltage
w i l l exceed the negative an titrip v oltage and actuate
the relay. VR3 pro\' ides course adj u stm ent for relay
sensitivity.
Relay hold time w i l l be determ ined by
DELAY
control
V R 2 .
T h e tone oscillator
Q7. 2SC3 73
operates w hen . the
MODE
sw itch is in
CW
pos ition It is a phasesh ift
oscillator opera ting at appro x i matel y
800
Hz.
The tone
output is activated by the keying circuit and coupled
th rough
SIDETO N E L
EV
EL
control
V R · 1
to the receiver
audio ampli fier for sidetone m on itoring i n
CW
operation.
The ou tput from
Q7
is a l so cou pled to the
VOX
ampl i fier
QI!
for brea k - i n
cv.·
operat ion.
( 5 )
MO
D
U
L
A
TO
R
U N IT ( PB 1 1 84A )
The
MODU LATOR U � IT
contains the carrier osci l
lators. t h e r i n g mod u lator ci rcu it for
SSH.
a n d
.-\ M
modu lator. The carrier oscil lator oscill ates either
:�
178.5
K Hz
for
USK
or
3 1 81 .5
K Hz
for
LSB.
depend i ng upon
X ,
Q ,
X 2
TC 6
x ,
Q z
Modula tor Module ( PB 1 1 84 )
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