CHAPTER 3: AMPLITUDE MODULATION

If the plate supply voltage for a plate-modulated class C amplifier is

V, the maximum plate-cathode voltage could be almost as high as

a. 4V

b. 3V

c. 2V

d. 1V

A

In a low-level AM system, amplifiers following the modulated stage must

be

a. linear devices

b. harmonic devices

c. class C amplifiers

d. nonlinear devices

A

If the carrier of a 100 percent modulated AM wave is suppressed, the

percentage power saving will be

a. 50

b. 150

c. 100

d. 66.66

D

Leak-type bias is used in a plate-modulated class C amplifier to

a. prevent tuned circuit damping

b. prevent excessive grid current

c. prevent overmodulation

d. increase the bandwidth

B

The output stage of a television transmitter is most likely to be a

a. plate-modulated class C amplifier

b. grid-modulated class C amplifier

c. screen-modulated class C amplifier

d. grid-modulated class A amplifier

B

The modulation index of an AM wave is changed from 0 to 1. The

transmitted power is

a. unchanged

b. halved

c. doubled

d. increase by 50 percent

D

One of the advantages of the base modulation over collector modulation

of a transistor class C amplifier is

a. the lower modulating power required

b. higher power output per transistor

c. better efficiency

d. better linearity

A

A carrier is simultaneously modulated by two sine waves with modulation

indices of 0.3 and 0.4, the total modulation index

a. is 1

b. cannot be calculated unless the phase relations are known

c. is 0.5

d. is 0.7

C

Amplitude modulation is used for broadcasting because

a. it is more noise immune than other modulation systems.

b. Compared with other systems it requires less transmitting power

c. its use avoids receiver complexity.

d. no other modulation system can provide the necessary bandwidth for

high fidelity

C

What is the ratio of modulating power to total power at 100 percent

modulation?

a. 1:3

b. 1:2

c. 2:3

d. None of the above

A