Modulation And Demodulation MCQs with Explanations

Understanding Modulation: Imagine a radio station broadcasting. The carrier is like the main, constant radio wave. The signal is the information (music, voice) being sent. Modulation changes the carrier wave based on the signal. Think of it like changing the volume (amplitude modulation) of the carrier wave according to the signal's strength. In this question: The carrier's voltage is 100V (this is the constant part). The signal makes the carrier voltage vary between 160V (highest) and 40V (lowest). Calculating Modulation Factor (m): The modulation factor shows how much the carrier's amplitude changes due to the signal. It's calculated as follows: m = (Vmax - Vmin) / (2 * Vc) Where: * Vmax = Maximum voltage of the modulated carrier (160V) * Vmin = Minimum voltage of the modulated carrier (40V) * Vc = Voltage of the unmodulated carrier (100V) Let's calculate: m = (160V - 40V) / (2 * 100V) = 120V / 200V = 0.6 The modulation factor (m) is 0.6. However this value is not present in option. Another approach to calculate modulation factor: m = (Vmax -Vc)/Vc m = (160-100)/100 = 0.6 or m = (Vc-Vmin)/Vc m = (100-40)/100 = 0.6 Since 0.6 is not an option, the correct answer is D: None of the above .

The correct answer is Option A: 20% . Here's why: Modulation percentage in Amplitude Modulation (AM) tells us how much the amplitude of the carrier signal changes. It's calculated using the formula: Modulation Percentage = [(Amax - Amin) / (Amax + Amin)] * 100 Where: Amax is the maximum amplitude of the modulated signal. Amin is the minimum amplitude of the modulated signal. In this problem: Amax = 60 Amin = 40 So, let's plug in the values: Modulation Percentage = [(60 - 40) / (60 + 40)] * 100 Modulation Percentage = [20 / 100] * 100 Modulation Percentage = 0.2 * 100 Modulation Percentage = 20% Therefore, the percentage of modulation is 20% .

Lower frequencies are easier to amplify is the correct answer to “In a superhetrodyne receiver, the difference frequency is chosen as the IF rather than the sum frequency because ___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Transmitter is the correct answer to “Modulation is done in ___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Radio receiver is the correct answer to “Demodulation is done in ___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

06 kW is the correct answer to “In the above question, what is the power in sidebands”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Obtaining lower fixed intermediate frequency is the correct answer to “Superhertodyne principle refers to”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

25% is the correct answer to “At 100% modulation, the power in each sideband is ___________ of that of carrier”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Crystal is the correct answer to “In a transmitter ___________ oscillator is used”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Sideband is the correct answer to “If level of modulation is increased ___________ power is increased”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Greater than is the correct answer to “Overmodulation (amplitude) occurs when signal amplitude is ___________ carrier amplitude”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Equal to is the correct answer to “If modulation is 100% then signal amplitude is ___________ carrier amplitude”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Amplitude is the correct answer to “Man made noise are ___________ variations.”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Amplitude is the correct answer to “In TV transmission, picture signal is ___________ modulated”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Frequency is the correct answer to “In TV transmission, sound signal is ___________ modulated”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

IF is the correct answer to “Most of the amplification in a superhetrodyne receiver occurs at ___________ stage”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

IF is the correct answer to “The superhetrodyne principle provides selectivity at ___________ stage”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Selectivity is the correct answer to “A high Q tuned circuit will permit an amplifier to have high ___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Fidelity is the correct answer to “If a radio receiver amplifies all the signal frequencies equally well, it is said to have high ___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Twice is the correct answer to “In amplitude modulation, bandwidth is ___________ the audio signal frequency”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Amplitude is the correct answer to “In amplitude modulation, the ___________ of carrier is varied according to the strength of the signal.”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

50 kW is the correct answer to “A 50 kW carrier is to be amplitude modulated to a level of 85%. What is the carrier power after modulation”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Reception is less noisy is the correct answer to “The major advantage of FM over AM is ___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Carrier is the correct answer to “In an AM wave, the majority of the power is in ___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Remains the same is the correct answer to “As the modulation level is increased, the carrier power ___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

May be any of the above is the correct answer to “Modulation refers to a low-frequency signal controlling the ___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

RF stage is the correct answer to “In a radio receiver, noise is generally developed at ___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

After several stages of amplification is the correct answer to “The diode detector in an AM radio receiver is usually found ___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Increase the Q of tuned circuit is the correct answer to “The function of ferrite antenna is to ___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

µV is the correct answer to “The signal voltage induced in the aerial of a radio receiver is of the order of ___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Amplitude is the correct answer to “In India, ___________ modulation is used for radio transmission”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Frequency modulation is the correct answer to “When the modulating signal controls the frequency of the carrier, we get___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Sidebands is the correct answer to “In an AM wave useful power is carrier by ___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Hartley is the correct answer to “In a radio receiver, we generally use ___________ oscillator as a local oscillator”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Space is the correct answer to “In radio transmission, the medium of transmission is ___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

RF and local oscillator signal is the correct answer to “In superhetrodyne receiver, the input at mixer stage is ___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Distortion is the correct answer to “Overmodulation results in ___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Automatic volume control is the correct answer to “The letters AVC stand for ___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

Radio frequency is the correct answer to “In a TRF radio receiver, the RF and detection stages are tuned to ___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.

1310 kHz is the correct answer to “The IF is 455 kHz. If the radio receiver is tuned to 855 kHz, the local oscillator frequency is ___________”. This question is standard in competitive examination syllabi for Modulation And Demodulation.