TM 11-5826-225-25
unit front panel is a dc microammeter requir-
operation of bfo Q21 by supplying or removing
emitter and base bias voltages. A regulated
ing 100 microampere of current for full-scale
source of + 15 volts dc is connected to one side
d e f l e c t i o n . The negative side of M301 is
of BFOOFF switch S301. Setting the switch
grounded and the positive side is connected to
of BFO, applies proper bias voltages to Q21
the cathode of meter rectifier CR10 through a
causing it to oscillate. When the BFOOFF
low-pass filter comprising R40, L15, C117, and
switch is set to OFF, bias voltage is removed
C114. The current flowing through M301 is the
and transistor Q21 cannot oscillate. The bfo
is used for tuning to zero beat when receiving
half wave, rectified, positive cycles of signal
continuous wave (C W) signals. For bfo circuit
present at the output of IF transformer T17.
functioning, refer to paragraph 1-14.
This current is proportional to the amplitude
of IF amplifier signal and reaches maximum
1-32. Receiver Tuning Meter
amplitude when the receiver is tuned to the
RF carrier of a radio station. The receiver is
tuned for maximum tuning meter indication.
Tuning meter M301 mounted on the control
Figure 1-19. Remover tuning meter, schematic diagram.
1-30 Change 5
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