used with IN270 diodes employed for detection.
discriminator appears across audio gain control R9.
AUDIO AND SQUELCH CIRCUITS
The audio signal is fed from the volume control through a 0.02-microfarad
capacitor to the base of transistor Q13, which is directly coupled to the audio
output stage Q14. The collector of Q14 feeds the transducer horn or the earphone
Squelch is provided through noise amplifier Q11,
The squelch is activated when the
volume control is first turned on.
deactivate the squelch voltage when the volume control reaches the maximum point on
The squelch threshold control, R8, is an internal adjustment and
Power for this receiver is supplied by a 6-volt battery through switch S1.
Silicon diode CR6 furnishes the bias for audio stage Q14.
Inductors L2, L3, L4,
L5, L6, L9, and L10 isolate the individual stages.
In each of the following exercises, select the ONE answer that BEST completes
the statement or answers the question.
Indicate your solution by circling the
letter opposite the correct answers in the subcourse booklet.
1. Squelch circuits are often incorporated in FM receivers to remove background
noise during the time that a signal is not being received.
voltage can be used to provide a reduction of background noise by applying the
voltage to the
a. discriminator through a squelch tube.
d. discriminator plates as a negative bias.
2. The voltage to operate a squelch tube is usually derived from another part of
the receiver. The stages that may be used to supply the voltages include the