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~~M~!~ATIDNB
5""'11_
DIVIBION
normal sound to the transmitted voice sig-
nal.
The output
is taken via C136,
with
C147 providing
bypassing
for RF
energy.
When operating
in the CW mode,
or in the
receive condition,
the amplifier is
dis-
abled by voltages applied through
CR120
or CRl19,
respectively, and through R161,
to the inverting input
of the amplifier,
causing
its
output
to go to
its lowest
limit and remain there
so long as
these
voltages are present,
preventing it from
amplifying the transmit audio signal.
CI!S
RI62
FROM
MIC GAlM
CI!4
î
CIM
o
~U~OD
+ (
ot
CRlt9
~C147
R lINE
Rlel
CRI20
RI60
Clf LINt:
'='
RIS.
'='
MODULATION AMPLIFIER
BALANCED MOIDLATOR
R
loe
.IV
A.~
..........oe
Rloa
.IV
e.70
~
RI.
CW DftfVE
W'''E.1It
o-<I~lV'v-+{
CI72
t
ou.
11180
"='
OSCILLATOft
SWITCH'N.
AIID ItAUNCtD MCXlULATClR
Cl73
.~:: ~t-'\I'V\r+-i-{
osc.
ZlOl, on the exciter board, used as the first mixer in the receive con-
dition, is used as the
balanced modulator in the transmit condition.
Audio
from the
modulation
amplifier
is applied to ZlOl through
RIOl and RI02.
Meanwhile,
the P.A. bias line,
which goes low for transmit, cuts off Q116,
removing the voltage applied through R180 and CRI05 from the emitter of Ql17
which allows it
to operate as a normal amplifier.
This voltage, present in
the receive
condition,
reverse biases
the base-emitter junction of Q117, dis-
abling it when it is not needed.
Carrier oscillator energy is coup-
led through
C173 and Rl84
to the base
of Q1l7, where
i t is
amplified.
Out-
put is taken from the emitter, through
R181 and Cl71,
and applied to the base
of Q101.
(In the
receive
condition,
local oscillator
energy is coupled th-
rough Ql15
to
the
base of Q101,
but
this path is interrupted in
the trans-
mit condition).
Q101 is a feedback
am-
plifier,
with its
gain
determined by
the ratio of
feedback resistor RI05 to
the
input series resistor, R18l.
Bias
and emitter circuits
are conventional,
and output is taken from the collector
.of QlOl
through a winding
internal to
ZlOl.
The
DSB suppressed-carrier out-
put is
taken
through
cl06.
(For
internal circuitry of Zlül, see the servicing Hints section of this manual.l
FIRST I. F. !NOISE
BLANKER
GATE
The DSBSC output
of ZlOl is coupled to the first I.F. amplifier, Ql03,
via cl06.
Rlll and Rl12 form the bias network,
while emitter resistor RIIO
is unbypassed,
providing
some degenerative feedback.
Output is developed
across a parallel-tuned resonant circuit composed of the primary of TIOl and
Cl09.
Rl14 and CI07 form a decoupling network, while the latter also places
the upper end of the
primary of TIOl at AC ground.
4-2
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