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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.
| 751. |
A photo diode converts light signals to binary. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 752. |
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 | |
| 753. |
A diode detector load consists of 0.01 μF capacitor in parallel with a 5 k ohms resistor. The maximum depth of modulation without diagonal clipping at modulating frequency of 1000 Hz and 10 kHz is |
| A. | 0.76, 0.24 |
| B. | 0.95, 0.3 |
| C. | 0.24, 076 |
| D. | 0.3, 0.95 |
| Answer» C. 0.24, 076 | |
| 754. |
The storage capacity of a CD is |
| A. | 360 k bytes per side |
| B. | 360 M bytes per side |
| C. | 540 k bytes per side |
| D. | 540 M bytes per side |
| Answer» E. | |
| 755. |
It is required to increase the maximum range of a radar by a factor of two. The peak power transmitted in the radar system has to be increased by a factor of |
| A. | 2 |
| B. | 4 |
| C. | 8 |
| D. | 16 |
| Answer» B. 4 | |
| 756. |
Assertion (A): CCIR-B system has 625 scanning lines per frame and 2 : 1 interlace.Reason (R): The aspect ratio is 4 : 3 |
| 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» C. A is correct but R is wrong | |
| 757. |
A frequency doubler has an FM signal input at 13 MHz with a deviation of 5 kHz. The output frequency of the carrier will be |
| A. | 26 kHz |
| B. | 260 kHz |
| C. | 26 MHz |
| D. | 260 MHz |
| Answer» E. | |
| 758. |
In EM waves, polarization |
| A. | is always vertical in an isotropic medium |
| B. | is caused by reflection |
| C. | is due to transverse nature of waves |
| D. | results from longitudinal nature of waves |
| Answer» D. results from longitudinal nature of waves | |
| 759. |
In the FM wave described by equation v = 15 sin (4 x 108 t + 3 sin 1100 t), the carrier frequency and signal frequency respectively are |
| A. | 63.66 MHz and 175 Hz |
| B. | 4 x 108 Hz and 1100 Hz |
| C. | 175 Hz and 63.66 MHz |
| D. | 1100 Hz and 4 x 108 Hz |
| Answer» B. 4 x 108 Hz and 1100 Hz | |
| 760. |
In the above case the total power in the modulated wave double sideband, suppressed carrier AM will be |
| A. | 112 W |
| B. | 400 W |
| C. | 415 W |
| D. | 512 W |
| Answer» C. 415 W | |
| 761. |
Which camera tube has highest sensitivity and very wide spectral response? |
| A. | Vidicon |
| B. | Plumbicon |
| C. | New vicon |
| D. | Saticon |
| Answer» D. Saticon | |
| 762. |
Audio systems use transverse recording. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 763. |
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 | |
| 764. |
A message signal with bandwidth 10 kHz is lower sideband SSB modulated with carrier frequency fc1 = 106 Hz. The resulting signal is then passed though a narrow band frequency modulator with carrier frequency fc2 = 109 Hz. The bandwidth of the output would be |
| A. | 4 x 104 Hz |
| B. | 2 x 106 Hz |
| C. | 2 x 109 Hz |
| D. | 2 x 1010 Hz |
| Answer» C. 2 x 109 Hz | |
| 765. |
A digital watch contains |
| A. | quartz crystal oscillator |
| B. | RC oscillator |
| C. | LC oscillator |
| D. | either quartz or RC oscillator |
| Answer» B. RC oscillator | |
| 766. |
For AM receivers the standard IF frequency is |
| A. | 106 kHz |
| B. | 455 kHz |
| C. | 1.07 MHz |
| D. | 10.7 MHz |
| Answer» C. 1.07 MHz | |
| 767. |
To avoid objectionable noise in a microwave TV link, the SNR should be about |
| A. | 50 or more |
| B. | 10 or more |
| C. | 25 or more |
| D. | 200 or more |
| Answer» D. 200 or more | |
| 768. |
Some features of advanced mobile phone service are To provide telephone communication to a large number of telephone users within the area of a metropolitan onlyTo use minimum amount of frequency spectrumTo permit hand held as well as vehicle operation of telephone Which of the above are true? |
| A. | 1 and 2 only |
| B. | 1, 2, 3 |
| C. | 1 and 3 only |
| D. | 2 and 3 only |
| Answer» C. 1 and 3 only | |
| 769. |
TDM |
| A. | can be used with PCM only |
| B. | interleaves pulses belonging to different transmissions |
| C. | combines five groups into a super group |
| D. | stacks 24 channels in adjacent frequency slots |
| Answer» C. combines five groups into a super group | |
| 770. |
The main function of a balanced modulator is to |
| A. | produce balanced modulation of a carrier wave |
| B. | produce 100% modulation |
| C. | suppress carrier signal in order to create a single-sideband or double sideband |
| D. | limit noise picked by a receiver |
| Answer» C. suppress carrier signal in order to create a single-sideband or double sideband | |
| 771. |
A transmitter power of 10 W is increased by 30 dB. The effective radiated power is |
| A. | 100 W |
| B. | 1000 W |
| C. | 10000 W |
| D. | 100000 W |
| Answer» D. 100000 W | |
| 772. |
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 | |
| 773. |
In push pull amplifier, each transistor conducts for |
| A. | 180° |
| B. | 360° |
| C. | 90° |
| D. | 45° |
| Answer» B. 360¬∞ | |
| 774. |
Which one of the following blocks is not common in both AM and FM receivers? |
| A. | RF amplifier |
| B. | Mixer |
| C. | IF amplifier |
| D. | Slope detector |
| Answer» E. | |
| 775. |
The unit for luminous energy is |
| A. | lumens/sec |
| B. | lumens/m2 |
| C. | lumen-sec |
| D. | lumen/m |
| Answer» D. lumen/m | |
| 776. |
Tape recorders use |
| A. | cone type loudspeakers |
| B. | horn type loudspeakers |
| C. | either cone type or horn type loudspeakers |
| D. | none of the above |
| Answer» B. horn type loudspeakers | |
| 777. |
Which of the following codes is based on BCD format? |
| A. | EBCDIC |
| B. | ASCII |
| C. | Hollerith |
| D. | both (a) and (b) |
| Answer» E. | |
| 778. |
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 | |
| 779. |
If in a broadcasting studio, a 1000 kHz carrier is modulated by an audio signal of frequency range 100-5000 kHz, the width of channel is __________ kHz. |
| A. | 5 |
| B. | 4.9 |
| C. | 995 |
| D. | 10 |
| Answer» E. | |
| 780. |
AM-SC stands for |
| A. | Amplitude Modulated-Suppressed Carrier |
| B. | Amplitude Modulated-Single Carrier |
| C. | Amplitude Modulated-Synchronous Carrier |
| D. | Amplitude Modulated-Self Carrier |
| Answer» B. Amplitude Modulated-Single Carrier | |
| 781. |
Probability density function of thermal noise is |
| A. | Poisson |
| B. | Binomial |
| C. | Gaussian |
| D. | None of the above |
| Answer» B. Binomial | |
| 782. |
Which of the following are useful in comparing the noise performance of receivers? Input noise voltageNoise figureNoise resistanceNoise temperature Select answer as per the following codes: |
| A. | 1, 2 and 3 |
| B. | 1, 3 and 4 |
| C. | 2, 3, 4 |
| D. | 1, 2, 4 |
| Answer» D. 1, 2, 4 | |
| 783. |
The modulation index of wideband FM signal is |
| A. | less than unity |
| B. | unity |
| C. | greater than unity |
| D. | nearly 0.67 |
| Answer» D. nearly 0.67 | |
| 784. |
For maximum output the width of air gap of audio head should be |
| A. | equal to wavelength |
| B. | half the wavelength |
| C. | one quarter the wavelength |
| D. | very small as compared to wavelength |
| Answer» C. one quarter the wavelength | |
| 785. |
A radar beacon is a small radar set having a receiver, a separate transmitter and an antenna. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 786. |
When the modulating frequency is doubled, the modulation index is halved and the modulating voltage remains constant. The modulation system is |
| A. | FM |
| B. | AM |
| C. | phase modulation |
| D. | none of the above |
| Answer» B. AM | |
| 787. |
In a colour TV receiver the bandwidth of RF amplifier is |
| A. | exactly equal to channel width |
| B. | a little less than channel width |
| C. | a little more than channel width |
| D. | either (a) or (b) |
| Answer» D. either (a) or (b) | |
| 788. |
The difference between phase and frequency modulation |
| A. | is purely of academic interest |
| B. | lies in the different definitions of the modulation index |
| C. | lies in the poor audio response of phase modulation |
| D. | is too great to make the two systems compatible |
| Answer» C. lies in the poor audio response of phase modulation | |
| 789. |
For a bit rate of 8 kbps, the best possible values of the transmitted frequencies in a coherent binary FSK system are |
| A. | 16 kHz and 20 kHz |
| B. | 20 kHz and 32 kHz |
| C. | 20 kHz and 40 kHz |
| D. | 32 kHz and 40 kHz |
| Answer» E. | |
| 790. |
A video monitor is exactly similar to TV receiver. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 791. |
Consider the following differences between QPSK and MSK The side lobes in MSK are relatively much smaller in comparison to the main lobeThe spectrum of MSK has a main centre lobe which is 1.5 times as wide as the main lobe of QPSKThe waveforms of both MSK and QPSK exhibit phase continuity Which of the above statements are correct? |
| A. | 1 only |
| B. | 1 and 2 only |
| C. | 1, 2 and 3 |
| D. | 2 and 3 only |
| Answer» C. 1, 2 and 3 | |
| 792. |
Which one of the following is digital? |
| A. | Pulse code modulation |
| B. | Pulse width modulation |
| C. | Pulse frequency modulation |
| D. | Pulse position modulation |
| Answer» B. Pulse width modulation | |
| 793. |
The number of spectral component when two sine wave of same frequency multiplied is |
| A. | 2 |
| B. | 3 |
| C. | ‚àû |
| D. | 4 |
| Answer» C. ‚àû | |
| 794. |
Which one is digital modulation technique? |
| A. | AM |
| B. | PAM |
| C. | PCM |
| D. | None |
| Answer» E. | |
| 795. |
Dynamic range of hi-fi system is at least |
| A. | 150 dB |
| B. | 120 dB |
| C. | 80 dB |
| D. | 40 dB |
| Answer» D. 40 dB | |
| 796. |
In a TV, the output from RF tuner is about |
| A. | 1 μV |
| B. | 1000 μV |
| C. | 100 μV |
| D. | 0.5 μV |
| Answer» C. 100 ŒºV | |
| 797. |
The material used for the magnet of moving coil cone type loudspeaker is |
| A. | steel alloy |
| B. | soft iron |
| C. | hard steel |
| D. | Alnico |
| Answer» E. | |
| 798. |
Assertion (A): An electronic tuner uses varactor diodeReason (R): The capacitance of a varactor diode depends on the magnitude of reverse bias. |
| 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 | |
| 799. |
Which of the following frequency is likely to be associated with AM radio broadcast? |
| A. | 1000 kHz |
| B. | 100 MHz |
| C. | 500 MHz |
| D. | 10 GHz |
| Answer» B. 100 MHz | |
| 800. |
The maximum range of a transmitter depends on |
| A. | its frequency |
| B. | its power |
| C. | both its frequency and power |
| D. | none of the above |
| Answer» D. none of the above | |