( 3 )
LO\\.
FREQl ' E\CY
I F
l
'
\
IT
( PB118 3 B )
This modu le contains the low frt>q u ency IF amplifier.
CTYstal filtl'r. detector and A G C/S meter circuits.
On rt'Ct'iH'. a
3 180 !\ Hz
sign al from the n oise blanker
circuit is feel to the gall' of
QI
2SK 1 9GR, fET
from pin
] ;)
of the mod u le .
D1
·
[). 4
are diode switches w hich select tht' crystal
fil tt'r for SSB or CW reception. The 600 Hz C
W
filtt'r X F- 3 0C is an optional feat u re a\· ailable at additional
cost from you r dealer. The diode switch selects the
C W fil ter automatical l y w hen the 1\ 1 0 D E switch is set
to CW position . T his contro l rnltage is deriv ed from
pin
9
and
12.
The signal from the crystal fil tl'r is fed
to the base of Q2 .
2SC784R
and is amplified by Q2
and Q3 ,
TA-704SM
integrated circuit. The gain of
these two stages is controlled automatically by the
AGC voltage derived from AGC amplifier Q4,
2SC828Q.
The gain is also controlled manually by
the RF gain control on the front panel.
The output from Q3 is fed t h rough T 1 0 9 to the ring
demod u l ator
[)8 . J)l
I
for
CW
and
SSB
reception. The
carrier signal is feel to the detector from pin
5.
The
carrier signal is balanced by
V R I
to obtain minimum
distortion and also to a\·oid S-mctcr reading which
may be in fl u enced by the carrier oscil l ator signal. The
Q ,
T
109
VR ,
Low Frequency IF Module ( PB-1 1 83 )
A
B
B
/cl
A
S S B
on
:i•.l
-lll
L S B
U S B
.l i 8 1 "
3 l /h . '..>
'
� i "\I
C W A M
� :
) 1 j . •
FREQUENCY( KHz)
C H A R ACTER I STICS O F SSB/CW F ILTERS
A M
signal is detected by
D7 . 1 S 1 007
and fed to
the audio amplifier stage from pin 4 t h rough the
MODE
switch. T h e detected audio signa l s arc con n ected to
au dio amplifier u nit from pin
4
( A M ) and pin
6
( SSB & CW)
t h rough the lvfOD E switch on the front
panel and t he pn'- amplifier.
D� . 1 S 1 00 7 ,
D 6.
l S l S S S
AGC
rectifiers d rive the
ACC
amplifier
Q·1 .
The emitter o f Q 4 con tro l s S-meter
amplifier
Q5 .
2SC828Q.
On tran smit. the signal is applied to t he gate of
Ql
from pin
15 .
It is t h en amplified and passed th rough
the crystal fil ter. The output from the crystal filter 1s
applied to t lw high freq u rncy IF u nit from pin 1 0 .
03
BASE
03
X F30C
c w
L 3
l I
:CC?
C S
J:
X F 32A
S S B/ A M
Q I
0 2
CW F I LTER INSTALLATION D I A G R A M
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1 4 -
