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MCQOPTIONS
This section includes 1362 Mcqs, each offering curated multiple-choice questions to sharpen your Electronics & Communication Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 451. |
In narrowband FM, the modulation index is |
| A. | about 0.1 |
| B. | about 300 |
| C. | 2 |
| D. | 2 |
| Answer» B. about 300 | |
| 452. |
Speech amplifiers are usually operated as |
| A. | class A |
| B. | classes AB |
| C. | class B |
| D. | class C |
| Answer» B. classes AB | |
| 453. |
Which of the following modulation is analog in nature? |
| A. | PCM |
| B. | DPCM |
| C. | DM |
| D. | PDM |
| Answer» E. | |
| 454. |
An image uses 512 x 512 picture elements. Each element can take any of eight distinguishable levels. The maximum entropy in the above image will be |
| A. | 648 bits |
| B. | 144 bits |
| C. | 9.47 MHz |
| D. | 4.43 MHz |
| Answer» C. 9.47 MHz | |
| 455. |
In broadcast television, the number of lines per frame is chosen to be odd number to |
| A. | reduce the required bandwidth |
| B. | improve resolution |
| C. | reduce peak power requirement |
| D. | make interlacing easier |
| Answer» E. | |
| 456. |
Which of the following could be the equation for non-linear resistor shown in figure? |
| A. | a + be + ce2 + de3 |
| B. | a - be - ce2 - de3 |
| C. | a + be + ce2 - de3 |
| D. | a + be - ce2 - de3 |
| Answer» B. a - be - ce2 - de3 | |
| 457. |
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| A. | all heads are withdrawn |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 | |
| 458. |
Household tape recorders use |
| A. | separate motor for each operation |
| B. | only one motor for all operations |
| C. | one motor for capstan and another for take up reel |
| D. | a total of 3 motors |
| Answer» C. one motor for capstan and another for take up reel | |
| 459. |
Which of the following terms are applicable to troposcatter propagation? |
| A. | Faradays rotation |
| B. | SIOs |
| C. | Fading |
| D. | Atmospheric storms |
| Answer» D. Atmospheric storms | |
| 460. |
To separate channels in FDM receiver we have to use |
| A. | integration |
| B. | AND gate |
| C. | band pass filter |
| D. | differentiation |
| Answer» D. differentiation | |
| 461. |
The ratio for 100% amplitude modulation with identical total transmitted power (mf is modulation index of FM) is |
| A. | mf2 |
| B. | m2f |
| C. | mf3 |
| D. | m3f |
| Answer» C. mf3 | |
| 462. |
In the FM wave described by equation v = 15 sin (4 x 108 t + 3 sin 1100 t), the maximum frequency deviation is |
| A. | 175 Hz |
| B. | 525 Hz |
| C. | 3 Hz |
| D. | 58.33 Hz |
| Answer» C. 3 Hz | |
| 463. |
Which statement is incorrect for the signal x(t) = 5 sin (2p x 103t) sin (2p x 106t)? |
| A. | Upper side band frequency is 1001000 |
| B. | Carrier amplitude is 5 |
| C. | Lower sideband frequency is 990000 |
| D. | x(t) is DSB-SC |
| Answer» D. x(t) is DSB-SC | |
| 464. |
Convolution of x(t + 5) with impulse function δ(t - 7) is equal to |
| A. | x(t - 2) |
| B. | x(t + 12) |
| C. | x(t - 12) |
| D. | (t + 2) |
| Answer» B. x(t + 12) | |
| 465. |
If in a radio receiver, RF signal has a frequency of 800 kHz and local oscillator that of 1000 kHz, then at the output of the mixer, the frequencies found would be __________ kHz. |
| A. | 800 to 1000 |
| B. | 200, 800, 1000, 1800 |
| C. | only 200 |
| D. | only 1800 |
| Answer» D. only 1800 | |
| 466. |
A signal m(t) amplitude modulates a carrier Ac cos ωct. The final signal will be |
| A. | [Ac m(t)] cos ωct] |
| B. | Ac . [1 + m(t)] cos ωct |
| C. | Ac + [m(t)] cos ωct |
| D. | Ac cos ωct + m(t) |
| Answer» C. Ac + [m(t)] cos œâct | |
| 467. |
If transmitted power is 10 kW, the field strength at a distance d is 50 mV/m. If transmitted power is reduced to 2.5 kW, the field strength at the same point will be |
| A. | 25 mV/m |
| B. | 12.5 mV/m |
| C. | 6.25 mV/m |
| D. | 3.125 mV/m |
| Answer» B. 12.5 mV/m | |
| 468. |
If there are M equally likely and independent messages and M = 2N where N is an integer, the information in each message is equal to |
| A. | 2 N bits |
| B. | 4 N bits |
| C. | 1 |
| D. | |
| Answer» B. 4 N bits | |
| 469. |
For real and odd signals, the Fourier series coefficient an is |
| A. | purely imaginary |
| B. | purely real and even |
| C. | purely imaginary and odd |
| D. | purely real and odd |
| Answer» C. purely imaginary and odd | |
| 470. |
In a TV receiver there is no raster, no picture and no sound. The most likely defective stage is |
| A. | power supply unit |
| B. | video output circuit |
| C. | horizontal oscillator |
| D. | balun |
| Answer» B. video output circuit | |
| 471. |
Identical telephone numbers in different parts of a country are distinguished by their |
| A. | area codes |
| B. | office codes |
| C. | access digits |
| D. | language codes |
| Answer» B. office codes | |
| 472. |
In a CD player the speed of CD is |
| A. | constant at 500 rpm |
| B. | constant at 200 rpm |
| C. | varies from 200 to 500 rpm |
| D. | none of the above |
| Answer» D. none of the above | |
| 473. |
ADM stands for |
| A. | Angle Delta Modulation |
| B. | Angle Digital Modulation |
| C. | Adaptive Delta Modulation |
| D. | Adaptive Digital Modulation |
| Answer» D. Adaptive Digital Modulation | |
| 474. |
Vidicon and plumbicon operate on the principle of |
| A. | photo conduction |
| B. | photo emission |
| C. | photo voltaic |
| D. | none of the above |
| Answer» D. none of the above | |
| 475. |
TV signal strength when expressed in dB m has the reference of |
| A. | 10 μV/m |
| B. | 5 μV/m |
| C. | 2 μV/m |
| D. | 1 μV/m |
| Answer» E. | |
| 476. |
In which of the following frequency bands are the standard AM radio broadcast stations? |
| A. | MF |
| B. | HF |
| C. | VHF |
| D. | UHF |
| Answer» E. | |
| 477. |
The function of duplexer in a RADAR is |
| A. | to permit the use of same antenna for transmission and reception |
| B. | to provide gain to the transmitted power |
| C. | to amplify the received signal |
| D. | both (b) and (c) |
| Answer» B. to provide gain to the transmitted power | |
| 478. |
The power density spectrum of noise voltage of resistor R can be expressed as |
| A. | 2 kTR |
| B. | 1 kTR |
| C. | 0.5 kTR |
| D. | 0.25 kTR |
| Answer» B. 1 kTR | |
| 479. |
If a signal voltage Vs is accompanied by a noise voltage Vn the signal to noise ratio is |
| A. | |
| B. | |
| Answer» B. | |
| 480. |
An MTI compares a set of received echos with those received during the previous sweep. |
| A. | 1 |
| B. | |
| C. | 4.77 kHz |
| D. | 47.7 kHz |
| Answer» B. | |
| 481. |
Pre-emphasis circuit is used |
| A. | after modulation |
| B. | before modulation |
| C. | before detection |
| D. | after detection |
| Answer» C. before detection | |
| 482. |
In an AM wave the carrier and one of the side bands is suppressed. If m = 1, the percentage saving in power is |
| A. | 0.25 |
| B. | 0.5 |
| C. | 0.666 |
| D. | 0.833 |
| Answer» E. | |
| 483. |
The correct sequence of subsystem in an FM receiver is |
| A. | mixer, RF amplifier, limiter, IF amplifier, discriminator, audio amplifier |
| B. | RF amplifier, mixer, IF amplifier, limiter, discriminator, audio amplifier |
| C. | RF amplifier, mixer, limiter, discriminator, IF amplifier, audio amplifier |
| D. | mixer, IF amplifier, limiter, audio amplifier, discriminator |
| Answer» C. RF amplifier, mixer, limiter, discriminator, IF amplifier, audio amplifier | |
| 484. |
Higher order TDM levels are obtained by |
| A. | forming super master groups |
| B. | using A law |
| C. | using μ law |
| D. | dividing pulse width |
| Answer» E. | |
| 485. |
The first geostationary satellite was named |
| A. | Intelsat I |
| B. | Intelsat II |
| C. | Intelsat III |
| D. | Early bird |
| Answer» E. | |
| 486. |
Which of the following is a false statement about Armstrong modulation system? |
| A. | Equalization is unnecessary |
| B. | Frequency multiplication must be used |
| C. | AM |
| D. | PAM |
| Answer» D. PAM | |
| 487. |
The relation between bandwidth B, modulating frequency fm and frequency deviation Δf for a sinusoidally modulated FM signal is |
| A. | B = fm - Δf/ |
| B. | B = 2(fm - Δf) |
| C. | VHP range |
| D. | UHF range |
| Answer» C. VHP range | |
| 488. |
Which of the following has highest power gain? |
| A. | CE |
| B. | CC |
| C. | CB |
| D. | CB or CC |
| Answer» B. CC | |
| 489. |
During amplitude modulation, the phase angle of the modulating voltage changes by |
| A. | 0° |
| B. | 45° |
| C. | 90° |
| D. | 180° |
| Answer» B. 45¬∞ | |
| 490. |
FM has |
| A. | two sidebands only |
| B. | four sidebands only |
| C. | eight sidebands only |
| D. | infinite sidebands |
| Answer» E. | |
| 491. |
In case of stabilized reactance modulator AFC system |
| A. | phase modulator is converted into frequency modulation by equalizer circuit |
| B. | the discriminator must have a fast time constant to provide demodulation |
| C. | the higher discriminator frequency, the better oscillator frequency |
| D. | the discriminator frequency must be too low, or the system will fail |
| Answer» D. the discriminator frequency must be too low, or the system will fail | |
| 492. |
A UPS contains |
| A. | rectifier |
| B. | inverter |
| C. | either rectifier or inverter |
| D. | both rectifier and inverter |
| Answer» E. | |
| 493. |
A narrow band FM does not have the following feature |
| A. | it has two sidebands |
| B. | both sideband equal in magnitude |
| C. | both sideband have same Phase Difference |
| D. | it does not show Amplitude variation |
| Answer» D. it does not show Amplitude variation | |
| 494. |
Modulation is also called detection. |
| A. | 1 |
| B. | |
| C. | its frequency |
| D. | its power |
| Answer» C. its frequency | |
| 495. |
If the AF voltage is raised to 10 V, while the AM is dropped to 200 Hz, what is the deviation? |
| A. | 10 kHz |
| B. | 15 kHz |
| C. | 20 kHz |
| D. | 40 kHz |
| Answer» D. 40 kHz | |
| 496. |
Each of the following statements regarding frequency modulation is true except |
| A. | amplitude of the modulated wave remains the same as that of carrier wave |
| B. | the amount of variation of deviation from the original carrier frequency is determined by the frequency of the modulating signal |
| C. | the rate at which the frequency of modulated wave varies is determined by the frequency of the modulating signal |
| D. | frequency of modulated wave increases as the signal voltage increases and vice-versa |
| Answer» C. the rate at which the frequency of modulated wave varies is determined by the frequency of the modulating signal | |
| 497. |
The most frequent users of long distance VLF transmission is |
| A. | ship communication |
| B. | radio broadcasting |
| C. | TV broadcasting |
| D. | telephone and telegraph |
| Answer» B. radio broadcasting | |
| 498. |
If a sound wave has a frequency of 50 Hz, the wavelength is |
| A. | 66 m |
| B. | 6.6 m |
| C. | 0.66 m |
| D. | 0.066 m |
| Answer» C. 0.66 m | |
| 499. |
An AM signal and a narrowband FM signal with identical carriers, modulating signals and modulation index of 0.1 are added together. The resultant signal can be closely approximated by |
| A. | Broadband FM |
| B. | SSB with carrier |
| C. | DSB-SC |
| D. | SSB without carrier |
| Answer» C. DSB-SC | |
| 500. |
In TV transmitter, visual exciter may consist of Video processing unitVisual modulatorVSB filterDelay equaliserFrequency converter Which of the above are actually a part of visual exciter? |
| A. | 1, 2 and 3 |
| B. | 2, 3 and 4 |
| C. | 1, 2, 3 and 4 |
| D. | 1, 2, 3, 4 and 5 |
| Answer» E. | |