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DRAKE TR-4CW - Transmitter Circuitry

DRAKE TR-4CW
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DRAKE
The
IF
signal
from
T12
is
also
applied
to
V2
which
functions
as
a
diode
detector
and
an
audio
amplifier
in
the
AM
receive
mode.
The
output
of
this
stage
is
also
fed
to
the
Mode
switch
and
is
connected
to
V17
through
the
Audio
Gain
control
when
the
Mode
switch
is
in
the
X-AM
position.
The
output
of
V17
is
applied
through
the
audio
output
trans-
former
to
the
phone
jack,
J5,
and
to
pin
12
of
the
power
connector.
Also,
output
from
the
plate
of
V17
is
applied
to
the
anti
vox
rectifier,
D6,
through
the
ANTIVOX
control.
A
100
kHz
crystal
calibrator,
V5,
is
switched
on
when
the
Mode
switch
is
in
the
CAL
position.
Its
output
is
coupled
to
the
grid
of
the
RF
amplifier
V7.
The
S
meter
in
the
TR—4C
operates
in
a
bridge
circuit
with
the
plates
of
a
receiver
IF
amplifier,
V11,
and
the
transmitter
IF
amplifier,
V15
in
one
leg
of
the
bridge
and
plate
of
the
audio
output
tube
V17
in
the
other
leg.
Receiver
AGC
voltage
applied
to
V1
1
on
receive
and
transmit
causes
these
tubes
to
draw
less
current,
thus
unbalancing
the
bridge,
which
causes
the
S
meter
to
read
up
scale.
The
bridge
is
balanced
on
receive
by
the
ZERO
control.
On
transmit,
the
meter
may
rest
up
scale
with
no
modulation.
4-3.
TRANSMITTER
CIRCUITRY.
Audio
input
from
the
microphone
is
applied
to
one
section
of
the
microphone
amplifier
V18
where
it
is
amplified
and
applied
to
the
remaining
section
of
this
tube
through
one
section
of
the
XMTR
GAIN
control.
Output
from
the
cathode
of
the
second
triode
of
V18
is
applied
to
the
balanced
modulator
through.
the
Mode
switch
for
SSB
operation.
Out-
put
from
the
plate
is
applied
to
the
grid
of
the
AM
screen
modulator,
V14,
and
to
the
grid
of
the
first
VOX
amplifier
triode,
VI9A,
through
the
VOX
control.
The
output
from
V19A
is
rectified
by
the
VOX
rectifier,
D5,
and
the
resulting
positive
DC
voltage
is
applied
to
the
grid
of
the
relay
control
triode,
VI9B,
causing
it
to
conduct
and
to
close
the
transmit/receive
relay.
Audio
voltage
from
V17
is
rectified
by
the
anti
vox
rectifier,
D6,
which
supplies
negative
voltage
to
the
grid
of
VI9B,
and
preventing
it
from
conducting
and
closing
the
relay
when
the
microphone
picks
up
audio
from
the
speaker.
Cut
off
bias
for
the
relay
tube
is
obtained
from
a
voltage
divider.
When
the
microphone
push-to-talk
switch
is
activated
the
cut
off
bias
is
grounded,
causing
V19B
to
conduct
and
close
the
relay.
RF
from
the
9.0
MHz
crystal
oscillator
portion
of
the
product
detector
tube
V16
is
applied
to
the
balanced
diode
modulator
through
the
carrier
balance
control.
On
SSB
the
audio
from
V18
is
also
applied
to
the
balanced
modulator
and
the
result
is
a
double
sideband
suppressed
carrier
signal
which
is
applied
to
the
transmitter
IF
amplifier.
The
ampli-
fied
output
is
coupled through
T13
to
the
upper
or
lower
crystal
filter
where
the
undesired
sideband
is
filtered
out.
The
resulting
SSB
signal
is
coupled
through
T6
to
the
transmitter
mixer,
V4,
where
it
is
combined
with
a
premixer
signal
of
the
proper
frequency
to
give
output
on
the
desired
amateur
band.
Output
from
V4
passes
through
the
L/C
circuit,
T7,
T8
and
C37,
and
is
applied
to
the
grid
of
the
driver
tube,
V6.
Here
it
is
amplified
and
applied
to
the
grids
of
V8,
V9,
and
V10
through
the
L/C
network,
T9,
T10
and
the
other
half
of
C37.
Three
parellel
power
amplifier
tubes
boost
the
sig-
nal
to
a
power
level
suitable
for
transmission.
The
output
impedance
of
the
power
amplifier
tubes
is
matched
to
a
52
ohm
load
by
means
of
the
pi
net-
work
circuit
composed
of
L8, L9,
C94
and
C95.
At
the
first
trace
of
flat
topping
in
the
final
ampli-
fier
tubes,
a
small
amount
of
grid
current
will
be
drawn.
This
produces
a
voltage
drop
across
R47.
The
small
negative
going
voltage
thus
obtained
is
applied
through
R46
to
the
cathode
of
V13B
where
it
is
amplified.
The
amplified
negative
voltage
is
applied
to
the
grid
of
V15,
thus
reducing
the
level
of
the
driving
signal.
When
the
Mode
switch
is
placed
in
the
X-CW
position,
V2
becomes
an
audio
phase
shift
oscilla-
tor
which
is
grid-block
keyed
along
with
the
trans-
mitter
mixer,
V4,
and
the
driver,
V6.
The
audio
output
from
V2
is
applied
to
the
grid
of
the

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