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b. Voltage divider resistors R830 and
resistor R839 meters the voltage drop
R832 (fig. 14) bias the cathode of V802B
a c r o s s that resistor to indicate trans-
(fig. 20) positive with respect to the plate
mitter power amplifier plate current when
cutting off the tube. Potentiometer R831,
the METER switch is placed in the PA Ib
connected across secondary winding 10-11,
position. The metering circuit is shown in
of output transformer T802, controls the
figure 22, Sidetone audio is tapped off sec-
amplitude of the audio applied to the cath-
o n d a r y winding terminals 8-9, through
ode of V802B.
R 8 3 3 and applied to Radio Set Control
C-1439/U and front panel AUDIO jacks as
c. When the amplitude of audio signals on
described in paragraph 4 5 b .
the secondary winding increases so that the
peak audio voltage exceeds the R830 and
61. Limiter Rectifier V802B
R831 voltage divider bias, the negative half
(fig. 14 and 20)
cycles of audio signals cause the cathode of
limiter-rectifier V802B to go negative with
a. Limiter rectifier V802B monitors the
respect to the plate. This causes V802B to
modulation voltage developed across mod-
conduct. Tube V802B plate current through
ulation transformer T802 and limits the
resistors R841 and R819 develops a voltage
modulator output to a predetermined value.
drop which applies a negative bias voltage
W h e n the voltage across secondary ter-
to the control grid of V803. Capacitor C810
m i n a l s 10-11 exceeds the predetermined
maintains the negative bias on the grid of
value, a negative voltage is developed by
V803 while V802B is cutoff during positive
l i m i t e r rectifier V802B. This negative
half cycles of audio voltage. The negative
voltage is applied as bias to audio pream-
bias applied to the control grid of audio
plifier V803 and reduces the gain of V803;
preamplifier V803 lowers the gain of the
thereby, limiting the maximum voltage that
stage. Thus, the modulator output is auto-
can be developed across modulation trans-
matically limited.
former T802.


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