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MCQOPTIONS
This section includes 9294 Mcqs, each offering curated multiple-choice questions to sharpen your Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 8901. |
The circuit of figure give an output which is |
| A. | a frequency modulated signal |
| B. | an amplitude modulated signal |
| C. | a phase modulated signal |
| D. | none of the above |
| Answer» B. an amplitude modulated signal | |
| 8902. |
The amplitude of a modulated RF aerial current is 6 A on the peaks of modulation and 4 A on the troughs of modulation. The value of carrier amplitude is |
| A. | 5 |
| B. | 15 |
| C. | 20 |
| D. | 30 |
| Answer» B. 15 | |
| 8903. |
In practical commercial AM system channel bandwidth is |
| A. | 150 kHz |
| B. | 100 kHz |
| C. | 15 kHz |
| D. | 200 kHz |
| Answer» D. 200 kHz | |
| 8904. |
The currents fed to the two dipoles of turnstile antenna are |
| A. | in phase |
| B. | in quadrature |
| C. | in phase opposition |
| D. | either (a) or (c) |
| Answer» C. in phase opposition | |
| 8905. |
The storage capacity of audio CD is 540 Mb per side. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 8906. |
The device most likely to be found in an SSB transmitter is |
| A. | class C audio amplifier |
| B. | tuned modulator |
| C. | class B RF amplifier |
| D. | class A RF amplifier |
| Answer» D. class A RF amplifier | |
| 8907. |
Which of the following microphones has lowest output impedance? |
| A. | Moving coil |
| B. | Ribbon |
| C. | Crystal |
| D. | Condenser |
| Answer» C. Crystal | |
| 8908. |
In case of a low level AM transmitter, the amplifier modulated stage must be |
| A. | class A |
| B. | class B |
| C. | class B (linear) |
| D. | class C |
| Answer» D. class C | |
| 8909. |
Point out the false statement |
| A. | impulse noise voltage does not depend on bandwidth |
| B. | thermal noise is independent of frequency at which it is measured |
| C. | industrial noise is mostly of impulse type |
| D. | space noise is observable at frequencies in the range of 8 MHz and higher |
| Answer» B. thermal noise is independent of frequency at which it is measured | |
| 8910. |
In a low level AM system, the modulated amplifiers stage must be |
| A. | harmonic devices |
| B. | non-linear devices |
| C. | class C amplifier |
| D. | linear devices |
| Answer» E. | |
| 8911. |
In cell communication |
| A. | carrier frequency change |
| B. | carrier frequency constant |
| C. | depend upon location |
| D. | depend upon geographical area |
| Answer» B. carrier frequency constant | |
| 8912. |
A ground wave travels along surface of ground. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 8913. |
Homodyne detection means |
| A. | coherent detection |
| B. | non-coherent detection |
| C. | asynchronous detection |
| D. | none of the above |
| Answer» B. non-coherent detection | |
| 8914. |
A radio station works at 800 kHz and uses AM. If this is a public broadcast system, it should transmit using |
| A. | parabolic reflector to transmit all round |
| B. | turnstile antenna for the required land |
| C. | half wave long horizontal wave |
| D. | a vertical antenna less than quarter for practical reasons |
| Answer» E. | |
| 8915. |
In narrowband FM, the modulation index is |
| A. | near unity |
| B. | about 100 |
| C. | about 0.1 |
| D. | about 300 |
| Answer» B. about 100 | |
| 8916. |
A single-sideband (SSB) signal contains 3 kW. The power content of the carrier is __________ kW. |
| A. | 2 |
| B. | 2 |
| C. | 3 |
| D. | 0 |
| Answer» D. 0 | |
| 8917. |
Waves of frequencies higher than 30 MHz penetrate the atmosphere. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 8918. |
During fast forward operation of a tape recorder |
| A. | all heads are withdrawn |
| B. | all amplifiers are shut off |
| C. | tape is not pressed against capstan |
| D. | all of the above |
| Answer» C. tape is not pressed against capstan | |
| 8919. |
In a superheterodyne broadcast receiver, the frequency of local oscillator is __________ the incoming signal frequency. |
| A. | higher than |
| B. | lower than |
| C. | equal to |
| D. | not comparable to |
| Answer» B. lower than | |
| 8920. |
PCM : Quantising Noise :: Transistor : |
| A. | Partition noise |
| B. | Shot noise |
| C. | Whirl |
| D. | No noise |
| Answer» B. Shot noise | |
| 8921. |
PAL stands for |
| A. | Phase Attenuation by Line |
| B. | Phase Alternation by Line |
| C. | Parabolic Alternation by Line |
| D. | Picture Alternation by Line |
| Answer» C. Parabolic Alternation by Line | |
| 8922. |
In digital TV digital imaging standard comprises |
| A. | six profiles and four levels |
| B. | four levels and six profiles |
| C. | six profiles and six levels |
| D. | four profiles and four levels |
| Answer» B. four levels and six profiles | |
| 8923. |
In an SSB transmitter one is most likely to find |
| A. | class C audio amplifier |
| B. | tuned modulator |
| C. | class B RF amplifier |
| D. | class AB power amplifier |
| Answer» D. class AB power amplifier | |
| 8924. |
The antenna current of an AM transmitter is 8 A. When only the carrier is sent, but it increases to 8.93 A. when the carrier is sinusoidally modulated. The percentage modulation is nearly |
| A. | 90% |
| B. | 80% |
| C. | 75% |
| D. | 70% |
| Answer» E. | |
| 8925. |
The 2 out of 5 code has |
| A. | two 0s and three 0s in each code group |
| B. | one 1s and four 0s in each code group |
| C. | four 1s and one 0s in each code group |
| D. | three 1s and two 0s in each code group |
| Answer» B. one 1s and four 0s in each code group | |
| 8926. |
Which of the following modulation is analog in nature? |
| A. | PCM |
| B. | DPCM |
| C. | DM |
| D. | PDM |
| Answer» E. | |
| 8927. |
Consider the following statements as regards BPSK and QPSK: In BPSK we deal individually with each bit of duration TbIn QPSK we lump two bits to form a symbolIn both BPSK and QPSK signal changes occur at bit rateIn QPSK the symbol can have any one of four possible values Which of the above statements are correct? |
| A. | 1, 2, 3, 4 |
| B. | 1, 2, 3 |
| C. | 1, 2, 4 |
| D. | 2, 3, 4 |
| Answer» D. 2, 3, 4 | |
| 8928. |
In equally tampered musical scale, an octave is divided into |
| A. | 12 intervals |
| B. | 10 intervals |
| C. | 7 intervals |
| D. | 5 intervals |
| Answer» B. 10 intervals | |
| 8929. |
Figure of merit is always unity in |
| A. | AM |
| B. | SSB-SC |
| C. | FM |
| D. | All |
| Answer» C. FM | |
| 8930. |
In the spectrum of a FM wave |
| A. | the carrier frequency cannot disappear |
| B. | the carrier frequency disappears when the modulation index is large |
| C. | the amplitude of any sideband depends on the modulation index |
| D. | the total number of sidebands depends on the modulation index |
| Answer» D. the total number of sidebands depends on the modulation index | |
| 8931. |
The gap width in audio heads is about 0.01 mm. |
| A. | True |
| B. | False |
| Answer» C. | |
| 8932. |
Speeds of sound and radio waves are equal. |
| A. | True |
| B. | False |
| Answer» C. | |
| 8933. |
In PCM, bit duration is defined as |
| A. | <img src="/_files/images/electronics-and-communication-engineering/communication-systems/534-918-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/communication-systems/534-918-2.png"> |
| C. | sampling period x total no. of bits |
| D. | none of these |
| Answer» B. <img src="/_files/images/electronics-and-communication-engineering/communication-systems/534-918-2.png"> | |
| 8934. |
Assertion (A): If frequency is high, the distance between transmitter and antenna may be an appreciable fraction of wavelengthReason (R): Wavelength is inversely proportional to frequency. |
| A. | Both A and R are correct and R is correct explanation of A |
| B. | Both A and R are correct but R is not correct explanation of A |
| C. | A is correct but R is wrong |
| D. | A is wrong but R is correct |
| Answer» B. Both A and R are correct but R is not correct explanation of A | |
| 8935. |
The spectral component of noise associated with kth frequency is given, in the limit as f 0 by nk(t) written as nk(t) = Ck cos (2pk ft + k) Consider the following statements as regards Ck and k Ck and k are independent of one anotherCk and k are independent of the amplitude of a spectral component at a different frequencyCt and k are independent of the phase of a spectral component at a different frequency Which of the above statements are correct? |
| A. | 1, 2 only |
| B. | 1, 3 only |
| C. | 1, 2, 3 |
| D. | 2, 3 only |
| Answer» D. 2, 3 only | |
| 8936. |
In a modulator it is found that the amplitude spectrum consists a component at fc, the carrier frequency and one component each at fc - fs and fc + fs where fs is the modulating signal frequency. Then the modulator used is |
| A. | AM |
| B. | AM or MBFM with modulation index 0.5 |
| C. | FM |
| D. | PAM |
| Answer» C. FM | |
| 8937. |
Troposphere is the portion of atmosphere |
| A. | nearest to ground |
| B. | between 50 to 90 km above ground |
| C. | between 110 to 220 km above ground |
| D. | between 250 to 350 km above ground |
| Answer» B. between 50 to 90 km above ground | |
| 8938. |
Earth's curvature affects the effective height of antenna. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 8939. |
A narrowband amplifier is one that has a passband |
| A. | limited to 2000 Hz only |
| B. | limited to audio frequency range only |
| C. | near cut off region of active device |
| D. | approximately 10% of its central frequency |
| Answer» E. | |
| 8940. |
In PCM, the quantization noise depends on |
| A. | sampling rate |
| B. | signal power |
| C. | number of quantization level |
| D. | signal energy |
| Answer» D. signal energy | |
| 8941. |
The power density spectrum of noise voltage at the input of a network is Sni and that at the output of the network is Sno. If transfer function of network is H( ), the corresponding noise figure is |
| A. | <img src="/_files/images/electronics-and-communication-engineering/communication-systems/502-156-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/communication-systems/502-156-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/communication-systems/502-156-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/communication-systems/502-156-4.png"> |
| Answer» B. <img src="/_files/images/electronics-and-communication-engineering/communication-systems/502-156-2.png"> | |
| 8942. |
Pulse modulation is often used in |
| A. | microwave band |
| B. | FL band |
| C. | telegraphy |
| D. | telephony |
| Answer» D. telephony | |
| 8943. |
In a colour TV receiver, the function of comb filter is |
| A. | to pass only the clusters of monochrome signal energy while blocking chrome signals |
| B. | to pass only chrome signals and block monochrome signals |
| C. | to block both monochrome and chrome signals |
| D. | none of the above |
| Answer» B. to pass only chrome signals and block monochrome signals | |
| 8944. |
In AM the amplitude of carrier components ... while in FM it |
| A. | remains constant, does not remain constant |
| B. | does not remain constant ... remains constant |
| C. | remains constant... also remains constant |
| D. | does not remain constant, also does not remain constant |
| Answer» B. does not remain constant ... remains constant | |
| 8945. |
Which of the following form of angle modulation in this? If e = 10 sin(108 t + 3 sin 104 t) |
| A. | AM |
| B. | FM |
| C. | AM or FM |
| D. | AM or PCM |
| Answer» C. AM or FM | |
| 8946. |
The noise performance of a square law demodulator of AM signal is |
| A. | better than that of an envelope detector |
| B. | better than that of a synchronous detector |
| C. | identical with that of a synchronous detector |
| D. | poorer than that of an envelope detector |
| Answer» C. identical with that of a synchronous detector | |
| 8947. |
A communication receiver is |
| A. | TRF receiver |
| B. | a superheterodyne receiver |
| C. | either (a) or (b) |
| D. | neither (a) nor (b) |
| Answer» C. either (a) or (b) | |
| 8948. |
Which of the following microphones has bidirectional feature? |
| A. | Moving coil |
| B. | Ribbon |
| C. | Condenser |
| D. | Carbon |
| Answer» C. Condenser | |
| 8949. |
In TV transmitter some possible advantages of IF modulation are The modulator section and visual exciter can be solid state devicesVSB filter can be introduced at low power levelThe subsequent stages following VSB filter can be tuned permanently for wideband linear operationIt is economical which of the above are true? |
| A. | 1 and 2 |
| B. | 1, 2 and 3 |
| C. | 2, 3 and 4 |
| D. | 1, 2, 3 and 4 |
| Answer» E. | |
| 8950. |
A source is radiating power equally in all directions. If source power is P, the power density at distance d is |
| A. | <img src="/_files/images/electronics-and-communication-engineering/communication-systems/508-292-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/communication-systems/508-292-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/communication-systems/508-292-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/communication-systems/508-292-4.png"> |
| Answer» B. <img src="/_files/images/electronics-and-communication-engineering/communication-systems/508-292-2.png"> | |