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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-
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
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
R831 voltage divider bias, the negative half
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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