15. Good voltage regulation can be obtained in a modulator driver stage by using
a. zero-bias modulator tubes.
b. a regenerative-feedback circuit.
c. driver tubes with high plate impedances.
d. a driver transformer with the highest possible step-up turns ratio.
16. Each class of modulator has its own operating characteristics. The class of
modulator that gives the lowest plate circuit efficiency, power output, and
distortion is the one operated as class
a. AB1.
c. A.
b. AB2.
d. B.
17. The circuit of the volume compression system shown in figure 131
(TM 11-665) is so arranged that
a. the speech-amplifier tubes are required to amplify less than normal.
b. rectifier tube V2 operates continuously until a level of approximately
100-percent modulation is reached.
c. a positive voltage applied to the cathode
of
tube
V2
adjusts
the
modulation level to a predetermined value.
d. overmodulation is automatically prevented by applying AF voltage above a
predetermined value to the suppressor grid of the speech-amplifier tube.
18. The purpose of both high-level and low-level speech clippers is to
a. prevent the distortion caused by undermodulation.
b. provide means to eliminate the lower-than-average signal voltage.
c. permit the average peaks of the AF signal voltage to produce nearly 100-
percent modulation.
d. eliminate the undesirable high and low audio frequencies that are present
in speech but are not necessary for intelligibility.
19. In the low-level speech clipper shown in A of figure 132, TM 11-665, clipping
occurs when the bias voltages of the clipper diodes are
a. double the average value of the AF signal voltage.
b. equal to the average value of the AF signal voltage.
321 L2
11
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