Modulation & Demodulation Questions And Answers


Modulation & Demodulation Questions And Answers

  1. Modulation is done in …………..

Transmitter

Radio receiver

Between transmitter and radio receiver

None of the above

Answer : 1

  1. In a transmitter ……………. oscillator is used

Hartley

RC phase-shift

Wien-bridge

Crystal

Answer : 4

  1. In India, ……………. modulation is used for radio transmission

Frequency

Amplitude

Phase

None of the above

Answer : 2

  1. In an AM wave useful power is carrier by ………….

Carrier

Sidebands

Both sidebands and carrier

None of the above

Answer : 2

  1. In amplitude modulation, bandwidth is ……………. the audio signal frequency

Thrice

Four times

Twice

None of the above

Answer : 3

  1. In amplitude modulation, the ………… of carrier is varied according to the

strength of the signal.

Amplitude

Frequency

Phase

None of the above

Answer : 1

  1. Overmodulation (amplitude) occurs when signal amplitude is …………. carrier

amplitude

Equal to

Greater than

Less than

None of the above

Answer : 2


  1. In an AM wave, the majority of the power is in …………….

Lower sideband

Upper sideband

Carrier

None of the above

Answer : 3

  1. At 100% modulation, the power in each sideband is ………………… of that of

carrier

50%

40%

60%

25%

Answer : 4

  1. Overmodulation results in …………..

Weakening of the signal

Excessive carrier power

Distortion

None of the above

Answer : 3

  1. If modulation is 100% then signal amplitude is ………….. carrier amplitude

Equal to

Greater than

Less than

None of the above

Answer : 1

  1. As the modulation level is increased, the carrier power …………..

Is increased

Remains the same

Is decreased

None of the above

Answer : 2

  1. Demodulation is done in …………

Receiving antenna

Transmitter

Radio receiver

Transmitting antenna

Answer : 3

  1. A high Q tuned circuit will permit an amplifier to have high ……………

Fidelity

Frequency range

Sensitivity

Selectivity

Answer : 4

  1. In radio transmission, the medium of transmission is ……………..

Space

An antenna

Cable

None of the above

Answer : 1

  1. If level of modulation is increased ……………. power is increased

Carrier

Sideband

Carrier as well as sideband

None of the above

Answer : 2

  1. In TV transmission, picture signal is ……………… modulated

Frequency

Phase

Amplitude

None of the above

Answer : 3

  1. In a radio receiver, noise is generally developed at ………….

IF stage

Receiving antenna

Audio stage

RF stage

Answer : 4

  1. Man made noise are …………. variations.

Amplitude

Frequency

Phase

Both phase and frequency

Answer : 1

  1. The signal voltage induced in the aerial of a radio receiver is of the order

of …………….

mV

μV

V

None of the above

Answer : 2

  1. Superhertodyne principle refers to

Using a large number of amplifier stages

Using a push-pull circuit

Obtaining lower fixed intermediate frequency

None of the above

Answer : 3

  1. If a radio receiver amplifies all the signal frequencies equally well, it is said to

have high …………

Sensitivity

Selectivity

Distortion

Fidelity

Answer : 4

  1. Most of the amplification in a superhetrodyne receiver occurs at ………. stage

IF

RF amplifier

Audio amplifier

Detector

Answer : 1

  1. The letters AVC stand for …………..

Audio voltage control

Abrupt voltage control

Automatic volume control

Automatic voltage control

Answer : 3

  1. The superhetrodyne principle provides selectivity at ………. stage

RF

IF

audio

Before RF

Answer : 2

  1. In superhetrodyne receiver, the input at mixer stage is ……….

IF and RF

RF and AF

IF and AF

RF and local oscillator signal

Answer : 4

  1. The major advantage of FM over AM is …………..

Reception is less noisy

Higher carrier frequency

Smaller bandwidth

Small frequency deviation

Answer : 1

  1. When the modulating signal controls the frequency of the carrier, we get……….

Phase modulation

Amplitude modulation

Frequency modulation

May be any one of the above

Answer : 3

  1. Modulation refers to a low-frequency signal controlling the …………

Amplitude of the carrier

Frequency of the carrier

Phase of the carrier

May be any of the above

Answer : 4

  1. The IF is 455 kHz. If the radio receiver is tuned to 855 kHz, the local oscillator

frequency is ………….

455 kHz

1310 kHz

1500 kHz

1520 kHz

Answer : 2

  1. If Amin = 40 and Amax = 60, what is the percentage of modulation?

20 %

40 %

50 %

10 %

Answer : 1

  1. The function of ferrite antenna is to …………….

Reduce stray capacitance

Stabilise d.c. bias

Increase the Q of tuned circuit

Reduce noise

Answer : 3

  1. In a radio receiver, we generally use ………….. oscillator as a local oscillator

Crystal

Wien-bridge

Phase-shift

Hartley

Answer : 4

  1. A 100 V carrier is made to vary between 160 V and 40 V by the signal. What is

the modulation factor?

3

65

None of the above

Answer : 2

  1. A 50 kW carrier is to be amplitude modulated to a level of 85%. What is the

carrier power after modulation?

50 kW

5 kW

8 kW

25 kW

Answer : 1


  1. In the above question, what is the power in sidebands?

8 kW

6 kW

06 kW

9 kW

Answer : 3

  1. In a superhetrodyne receiver, the difference frequency is chosen as the IF

rather than the sum frequency because …………….

The difference frequency is closer to oscillator frequency

Lower frequencies are easier to amplify

Only the difference frequency can be modulated

None of the above

Answer : 2

  1. The diode detector in an AM radio receiver is usually found ………….

Before the first RF stage

After the first RF stage

After several stages of amplification

None of the above

Answer : 3

  1. In a TRF radio receiver, the RF and detection stages are tuned to …………

Radio frequency

IF

Audio frequency

None of the above

Answer : 1

  1. In TV transmission, sound signal is ………………… modulated

Amplitude

Frequency

Phase

None of the above

Answer : 2

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