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OCUBIC
COMMUNICATIONS
S.,A_
DIVIBION
eZI8
~
RI1I7
R/70
RI73
0118
""5
OUTPUT
AMPLIFIER
"211
~C181
EXT/INT
L.O.
SWITCHING
"'"
0117
CI79
~
Cl
8 2 D ' O
j
9
T
rrYY"'I
Irt
CRI08
TO lO
L__
~
~+-
....
..--o
OUTPUT
CI80
C 1 8 3 .
8UFFER
~
C18 ..
.I
R218
RI72
':"
-=
C/85
~
1t201
LO BANDPASS FILTERI BUFFER
RI71
..v'O-....-
...- - - - - -....- - ,
..--~"",,,,,,,,,,----+----"'JVv......-.o+VI60
j
FROM
L 0
o-t...
>-t-i.
MIlIER
is processed through one of six
bandpass filter-amplifier com-
binations.
Since
all
six are
identical
in
operation ,
only
the 160 meter version
will be
discussed here.
Collector and
switching
power comes from the 160 meter
control
line.
Rl?l
supplies
bias for
amplifier QIIJ,
and
also
biases
switch
CRIO? on;
the
voltage
drop
across
its
ground
return
resistor
(not
shown
in the
simplified
dia-
gram)
reverse
biases
similar
diode
switches
in
the
other
bandpass filter circuits.
QlIJ operates
without an emitter bypass capacitor,
and is therefore a .
bit degenerative;
its collector is composed of a parallel resonant circuit
forwed by TIO? and the Cl?9-C180
combination.
Output is taken from the low
impedance tap between these two capacitors,
and coupled through series res-
onant circuit
TI08-C18J,
then stepped
back up to
higher impedance
by
the
output
parallel
re sonant
circuit TI09-C182-Cl84.
Output switching is via
CRI08, biased on through Rl?J, the secondary of
TI09,
and R218.
C185 is a
bypass for the signal.
Again,
the voltage drop
across R218 reverse biases
the output
switching
diodes in
the other filters.
When
the PTO switch on the
front panel
is in the
EXTernal
position,
a voltage
is applied
through R191 to
CRl15,
and th-
ence
to
the
emitter
of L.O.
buffer Qll?
This reverse bias-
es
this
stage's
base--emitter
junction, preventing internally-
generated L.O. energy from be-
ing passed on.
At the same time
the voltage drop across R195 re-
verse biases CRl16
(since
the
INT
line is low) and Q118 acts
as a buffer for externally
sup-
plied L.O.
signal,
and
it is
passed on through
R196 and C215
to
the
L.O. output
amplifier,
Q120.
When
the PTO
switch is in,
any other than the EXT position,
the INT and"EXT voltages are re-
versed, and internally generated
L.O. signal is passed on to Ql20.
Ql20 and Ql21 are directly coupled, and amplify the L.O. signal select-
ed
by
the
switching circuit.
The emitter of Q120
is wired conventionally,
while R206 and R20? are the bias divider.
Feedback from the emitter of Ql21
-6
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