Frequency Modulation Question & Answers July 5, 2021 By WatElectronics This article lists 100+ Frequency Modulation MCQs for engineering students. All the Frequency Modulation Questions & Answers given below include a hint and wherever possible link to the relevant topic. This is helpful for the users who are preparing for their exams, interviews, or professionals who would like to brush up their fundamentals on the Frequency Modulation topic. Digital signals are preferred for transmission, but it is not always feasible as it needs high bandwidth with low pass characteristics. To overcome such issues analog transmission is considered, as it possesses low bandwidth and bandpass characteristics. Information about the source gets imposed on the carrier signal by modifying certain characteristics of it. This process in the analog transmission is termed modulation. Move the signal spectrum to a frequency that is less susceptible to attenuation in a medium is necessary. Further, the modulations are classified into two types. They are Amplitude modulation and angle modulation. Frequency modulation is part of an Angle modulation. 1). Modulation in which the carrier wave angle varies in accordance with the baseband signal is termed as ___________. Amplitude Modulation Angle Modulation Spectral Modulation None of the above Hint 2). The man behind the invention of frequency modulation is ______________. Edwin Howard Armstrong John Chowning Reginald Fessenden None of the above Hint 3). The original signal of source in modulation is known as _________. Baseband signal Attenuated signal Deviated signal Carrier signal Hint 4). Conversion of analog or digital data into analog form is known as ___________. Encoding Modulation Decoding Attenuation Hint 5). To encode the information in the carrier signal by altering the wave frequency instantaneously is known as ____________. Amplitude Modulation Frequency Modulation Phase Modulation None of the above Hint 6). What types categorized under Analog modulation? Amplitude Modulation Frequency Modulation Phase Modulation None of the above Hint 7). What are the various Frequency modulations? Analog FM Digital FM Both a and b None of the above Hint 8). Modulation index in frequency modulation can be determined by using _________. δf / fm Am/fm Am/Ac Ac/fm Hint 9). A carrier signal of 100 MHz modulated using a sine wave whose frequency is 75 kHz with a deviation frequency of 50 kHz. What will be the modulation index? 0.555 0.667 0.778 0.889 Hint 10). NBFM bandwidth is ________. fm 2fm (β+1) 2 fm fm (β+1) Hint 11). What is the basic difference between NBFM and AM signal? Bandwidth Frequency deviation Sidebands Algebraic sign reversal for the lower side frequency Hint 12). Bandwidth of WBFM is ________. fm 2fm (β+1) 2 fm fm (β+1) Hint 13). A 12 MHz carrier gets modulated by a sine signal with a frequency of 500 Hz bearing the frequency deviation of about 50 kHz. Find the bandwidth? 100 101 102 103 Hint 14). Based on modulation index FM is classified as __________. Multitone FM Narrow band FM (NBFM) Wide band FM (WBFM) Both b and c Hint 15). In NBFM the modulation index is ____________. Less than 1 Greater than 1 Infinity Can’t say Hint 16). Modulation of the source signal with multiple frequency components in it is called _______________. Amplitude Modulation Frequency Modulation Phase Modulation Multitone Modulation Hint 17). Modulation index will be greater than 1 in _________________. Amplitude Modulation Phase Modulation Narrow Band Frequency Modulation Wide band Frequency Modulation Hint 18). The transmitted power is independent of modulation index in _________________. Amplitude Modulation Frequency Modulation Phase Modulation None of the above Hint 19). Noise immunity is superior in ________________. Amplitude Modulation Frequency Modulation Phase Modulation None of the above Hint 20). Modulation index in Frequency modulation is proportional to _______________. Modulating frequency Modulating signal Both a and b None of the above Hint 21). In _____________ angle is in direct proportion with the integral of modulating signal. Amplitude Modulation Frequency Modulation Phase Modulation None of the above Hint 22). Departure of maximum instantaneous frequency from the carrier’s frequency is known as ________________. Amplitude deviation Phase deviation Frequency deviation Frequency shift keying Hint 23). Side bands present in frequency modulation are ____________. Finite Infinite Large Both b and c Hint 24). Total variation of frequency from its low to high point is termed as __________. Carrier swing Sideband width Frequency deviation None of the above Hint 25). In FM signals the amount of frequency deviated is dependent upon ________. Modulating frequency Carrier frequency Amplitude Phase Hint Frequency Modulation Multiple Choice Question & Answers 26). Sidebands in FM are controlled based on selected ____________. Modulating frequency Carrier frequency Deviation Phase Hint 27). Maximum deviation is due to __________. Transmitter Design Transmitter Configuration Both a and b None of the above Hint 28). Good audio quality needs ________. High deviation Low deviation Lesser deviation None of the above Hint 29). Human speech prefers _______. Higher deviation Lower deviation Larger deviation None of the above Hint 30). WBFM possess ________. High deviation Low deviation Lesser deviation None of the above Hint 31). If the deviation is +20 KHz indicates _________. Baseband is 20 KHz above fo Baseband is 20 KHz below fo Carrier is 20 KHz above fo Carrier is 20 KHz below fo Hint 32). What are the methods used to produce FM waves? Direct method Indirect method Both a and b None of the above Hint 33). The wave originated from the transmitter and its frequency varies concerning modulation source is possible in __________ of FM. Direct method Indirect method Both a and b None of the above Hint 34). Phase of the originated wave is a function of modulation in ______________ of FM. Direct method Indirect method Both a and b None of the above Hint 35). Armstrong method is categorized as ____________. Direct method Indirect method Both a and b None of the above Hint 36). _______________ is used to estimate the bandwidth of FM signal. Barkhausen criteria Nyquist rate Carson’s rule None of the above Hint 37). Spectrum of NBFM is similar to the spectrum of _____________. Amplitude Modulation Frequency Modulation Phase Modulation None of the above Hint 38). Carson’s rule formula for bandwidth calculation is _____________. fm 2fm (β+1) 2 fm 2(Δf+fm) Hint 39). The Δf in the Carson’s rule stands for _________. Peak deviation in frequency Required bandwidth Highest frequency Modulating frequency Hint 40). _____________ device is used to convert the received FM signal converted to voltage. PLL Frequency discriminator Envelope detector Oscillator Hint 41). Other than frequency discriminator ________ can be used for FM demodulation. PLL Frequency discriminator Envelope detector Oscillator Hint 42). FM is normally used above _____________ MHz. 20 30 40 50 Hint 43). What are the two common applications of frequency modulation? Two-way communications FM radio Both a and b None of the above Hint 44). An FM receiver consisting of Amplitude limiters serves the purpose of _________. Amplification Filteration Demodulation Removal of amplitude variations Hint 45). Circuit consisting of differentiator that allows to pass _______. High frequencies Low frequencies High voltages Low voltages Hint 46). __________ circuits are used in FM. Pre-emphasis De-emphasis Filteration Both a and b Hint 47). Boosting the high-level audio frequencies artificially according to the prearranged curve of response is known as ___________. Pre-emphasis De-emphasis Filteration Amplification Hint 48). ________ circuit used at the transmitter of FM. Pre-emphasis De-emphasis Filteration Amplification Hint 49). _______ circuit present at the receiver of FM. Pre-emphasis De-emphasis Filteration Amplification Hint 50). __________ filter is used in De-emphasis circuit. High pass Low pass Band pass Notch Hint Frequency Modulation MCQs for Exams 51). Parameters constant in FM are _____________. Amplitude Phase Frequency Both a and b Hint 52). Pre-emphasis is performed before ____________. Transmission Modulation Amplification Can’t say Hint 53). Pre-emphasis can be done __________.53). Pre-emphasis can be done __________. To boost the voltage of the modulating signal Modulation of signal at high frequencies Before modulation All the above Hint 54). What will be the change in bandwidth of the FM signal as the frequency of modulation tends to increase from 14 kHz to 28 kHz? 40 58 28 24 Hint 55). The characteristics of WBFM are _____________. Large Kf Wide Band width Both a and b None of the above Hint 56). The characteristics of NBFM are _________. Small Kf Narrow Bandwidth Both a and b None of the above Hint 57). PLL can be used as _______. AM demodulator FM receiver FM demodulator AM receiver Hint 58). NBFM operates at a range of ________ modulating frequencies. 30 Hz to 30 KHz 30 Hz to 3 KHz 3 KHz to 30 KHz 30 Hz to 15 KHz Hint 59). FM signal with 7 as modulation index applied to the ‘Frequency Tripler’. What will be the modulation index at the output obtained? 7 14 21 0 Hint 60). FM signal passed from mixer makes the deviation ____________. Reduce Double Halved Remains unaffected Hint 61). Digitally encoded data transmitted with frequency-modulated signals referred to as _________. Frequency-shift keying Phase-shift keying Amplitude-shift keying None of the above Hint 62). FM broadcast requires ____________ max. Bandwidth for commercial uses. 100 KHz 200 KHz 300 KHz 400 KHz Hint 63). The purpose of Guard bands in FM is to _________. Prevent adjacent channel interference Increase bandwidth Increase noise Both b and c Hint 64). In Armstrong method FM is obtained by using ____________. Amplitude Modulation Frequency Modulation Phase Modulation None of the above Hint 65). To generate WBFM, components present are _____. NBFM modulator Frequency multiplier Frequency converter All the above Hint 66). Frequency multiplier is a __________ device. Linear Non-linear Ideal None of the above Hint 67). What are the direct methods of FM generation? FM varactor diode modulator Armstrong method PLL direct FM transmitter Both a and c Hint 68). Parameter variation for FM generation is a ___________ method. Direct Indirect Armstrong None of the above Hint 69). Carrier is in phase with upper sidebands where the carrier is out of phase with the lower sideband in ____________. Amplitude modulation NBFM Phase modulation None of the above Hint 70). Crystal controlled oscillator used in FM generation is to provide ____________. Frequency deviation Increase bandwidth Increase noise Frequency stability Hint 71). NBFM signal’s frequency multiplied using frequency multiplier and produces _______. AM NBFM PM WBFM Hint 72). PLL is __________ feedback system. Positive Negative Zero Can’t say Hint 73). PLL FM detector can be used in ___________ applications. Analog Digital Both a and b None of the above Hint 74). PLL FM detector consists of _________________. Mixer Low pass filter VCO All the above Hint 75). Phase Locked Loop compares the input signal’s phase with the output signals phase using ________. Mixer Low pass filter VCO All the above Hint Frequency Modulation MCQs for Quiz 76). FM discriminator consists of ______________. Differentiator Envelope detector Limiter All the above Hint 77). To ensure the input signal amplitude in FM discriminator maintained constant __________ is used. Differentiator Envelope detector Limiter All the above Hint 78). Single slope discriminator has poor ____________. Linearity Non-linearity Ideal None of the above Hint 79). Two signals of FM in which one signal’s amplitude is twice the other strongest signal gets captured and weaker one gets rejected known as ___________. Linear effect Capture effect Carson’s rule None of the above Hint 80). ______________ improves the Signal to Noise ratio (SNR). Pre-emphasis De-emphasis Filteration Amplification Hint Read More About Frequency Modulation 81). AFC stands for _________________. Automatic Force Control Automatic Frequency Control Automatic Force Compulsion None of the above Hint 82). What are the advantages of Indirect method to generate FM? Frequency stability Frequency deviation Both a and b None of the above Hint 83). The maximum amount of deviation in frequency allowed for the broadcasting of FM commercially is __________. 50 KHz 75 KHz 85 KHz 100 KHz Hint 84). ____________ is an experimental technique utilized by FM systems to set the deviation of frequency with precision. FM varactor diode modulator Armstrong method PLL direct FM transmitter Bessel null method Hint 85). Audio oscillators analog output connected to the input of the buffer amplifier in _________ method. FM varactor diode modulator Armstrong method PLL direct FM transmitter Bessel null method Hint 86). VCO is used in _______ method to generate FM. Direct Indirect Both a and b None of the above Hint 87). ____________ method used in the generation of FM because the frequency of the oscillator varies directly based on the modulating signals. FM varactor diode modulator Armstrong method PLL direct FM transmitter Bessel null method Hint 88). What are the advantages of Varactor diode modulators of FM? Reliable Stability Simple All the above Hint 89). What is the drawback of Varactor diode modulators? Stability Linearity Complexity Frequency deviation Hint 90). FM circuit made using inductors known as ____________. FM saturable reactor modulator Armstrong method PLL direct FM transmitter Bessel null method Hint 91). Frequency Modulation can be achieved using _____________. PIN diode Klystron oscillators Multivibrators All the above Hint 92). Varactor diode in the frequency modulation is __________. Forward biased Reverse biased Neither forward not reverse None of the above Hint 93). VCO’s frequency of oscillations has _________dependent on the voltage applied. Linearly Non-linearly Inversely Can’t say Hint 94). Armstrong’s modulator using ‘frequency-up’ conversion involves __________ methods. FM saturable reactor modulator Heterodyne Multiplication Both b and c Hint 95). The modulator made using Armstrong method consists of ______________. Balanced modulator Phase shifter Multipliers and mixers All the above Hint 96). Desired deviation of frequency in Armstrong modulators can be attained using _________. Balanced modulator Phase shifter Multipliers and mixers All the above Hint 97). Which detector can detect either WBFM or NBFM modulated signals? PLL demodulator FM discriminator Quadrature FM detector Ratio detector Hint 98). Double tuned transformer for FM generation is used in ____________ detector. PLL demodulator FM discriminator Quadrature FM detector Ratio detector Hint 99). Noise suppressed without limiters in _______ detectors. PLL demodulator FM discriminator Quadrature FM detector Ratio detector Hint 100). What is the disadvantage of FM in comparison to AM? Lesser prone to noise interference Large Bandwidth needed Low power consumption All the above Hint Time is Up! Time's up
