TRANSMIT CIRCUIT
SSB MODE
The output from m icrophone jack J 2 is fed
through the MIC GAIN control VR3a to pin 8 o f
the AF UNIT.
AF UNIT (PB-1 964 )
The speech signal from pin 8 is amplified by micro
phone amplifier Q502
(TA 7063P)
and fed through
relay RL5 0 1 to the ring modulator, D502 - D 5 0 5 ,
where the speech signal modulates the carrier signal
delivered frpm Q s 1 3 . The resulting double sideband
signal is fed to the IF UNIT.
IF UNIT (PB- 1 96 3 )
The 8 . 9 8 7 5
MHz
double sideband signal is amplifi
ed by Q4o 1
( 3 SK5 1 - 03 )
and passed through side
band filter XF4o 1 by diode swit ches D403 , D409
( 1 S 1 5 55 ) ,
D4os ,
and D40 7
( 1 S 1 007 ) .
Here the
signal is converted to a single sideband signal by
removal o f the unwanted sideband .
The signal is then fed to buffer amplifier Q402
(2SK 1 9GR ) .
When the RF speech processor is
OFF , diode swit ches D4 1 1 and D4 1 2
( 1 S 1 5 5 5 )
fee d
the I F signal to IF amplifier Q40 5
( 3 SK5 1 -03 )
.
When the RF speech processor is ON, the S S B
signal is amplified by buffer amplifier Q402
( 2SK 1 9GR)
and further amplified by limiter Q403
(TA 7060P) ,
where signals that exceed the preset
clipping level are sliced out .
This highly clipped SSB signal is amplified b y
buffer amplifier Q4o4
( 2SC3 72Y)
and passed
through a s elective filter, XF403 , which removes
RF harmonics that result from signal clipping. The
signal is then fed to IF amplifier Q40 5 , and sub
sequently d elivered to the RF UNIT. The front
panel COMP LEVEL control, VR4 , controls t he
voltage at gate 2 of Q4o 1 , thus setting the processor
level.
The return of the grid circuit of the final amplifier
tubes is fed to Q406
(2SK 1 9BL),
which produces
ALC voltage. This voltage is fed to gate 1 of Q40 5 ,
controlling the gain o f this stage . When the RF
pro cessor is off, ALC voltage is also fed to gate 1
of Q40 1 . Q4o7
(2SA564 )
amplifies the ALC voltage
for indication on the front panel meter.
RF
UNIT (PB- 1 96 0 )
The IF signal is fed through T 104 to the transmit
mixer, consisting of parallel-connected Q 1 0 5 and
Q106
( 3 SK40M ) ,
where the IF signal at gate 1 is
mixed with the lo cal signal fed to gate 2 , p roducing
the RF output signal . The RF signal is then fed
through diode swit ch D 1 04
( 1 S 1 007)
to the
DRIVE UNIT.
DRIVE UNIT (PB- 1 7 1 4 ) , PA UNIT (PB- 1 7 1 5 )
The RF signal is amplified by driver V 1 6 o 1
( 1 2BY7 A ) ,
and delivered t o P A UNIT final
amplifier tubes V 1 7 0 1 and V 1 702
(6 1 4 6B ) .
The
output from the final tubes is fed to the antenna
jack .
A portion of the RF signal is coupled through C 1 4
t o the cathode o f the l 2BY7
A
driver, for the
purpose of improving the linearity of the final
amplifier. This technique is known as RF negative
feedback.
CW MODE
For CW, the 8 . 9 8 83 MH
z
carrier is generated by
oscillator Qs 14 at the frequency set by X 504 . The
carrier signal is fed through buffer Q5 1 3 and fed to
the ring modulator. The same carrier frequency is
used in the tune mode.
DC voltage is applied through diode swit ch D 5 1 7
( 1 S 1 5 5 5 )
and relay RL5 0 1 , unbalancing the ring
modulator for CW operation. The carrier signal is
then fed to the IF UNIT . The signal path is
identical to that on S S B , up to the D RIVE UNIT.
DRIVE UNIT (PB- 1 7 1 4 ) , PA UNIT (PB- 1 7 1 5 )
Keying o f the transmitter is accomplished b y
changing t h e bias voltage to the driver and final
tubes. During "key u p , " the tubes are cut off by
application of -3 5 volts to V 1 60 1 and - 1 1 0 volts
to V 1 70 1 and V 1 702 . These cutoff voltages are
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