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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.
| 551. |
Figure of merit is always unity in |
| A. | AM |
| B. | SSB-SC |
| C. | FM |
| D. | All |
| Answer» C. FM | |
| 552. |
In the spectrum of a frequency modulated wave |
| A. | carrier frequency cannot disappear |
| B. | carrier frequency vanishes when modulation index is large |
| C. | the number of significant sidebands depends upon modulation index |
| D. | none of the above |
| Answer» D. none of the above | |
| 553. |
Vestigial sideband is most commonly used in |
| A. | telephony |
| B. | all of the above |
| C. | 2097152 bits |
| D. | 786432 bits |
| Answer» C. 2097152 bits | |
| 554. |
Beam width of an antenna is expressed in |
| A. | metres |
| B. | degrees |
| C. | ratio of two powers |
| D. | ratio of two angles |
| Answer» C. ratio of two powers | |
| 555. |
The overall noise temperature Te, absolute temperature T and noise figure F are related as |
| A. | Te = T(F - 1) |
| B. | Te = F(T - 1) |
| C. | T = Te(F - 1) |
| D. | Te = (T)(F) |
| Answer» B. Te = F(T - 1) | |
| 556. |
An SSB-AM signal cannot be demodulated by |
| A. | Balanced modulator |
| B. | Complete phase shift generator |
| C. | Diode balanced modulator |
| D. | Product detector |
| Answer» B. Complete phase shift generator | |
| 557. |
CATV stands for |
| A. | Common Antenna Television |
| B. | Community Antenna Television |
| C. | Cable Antenna Television |
| D. | Channel Antenna Television |
| Answer» C. Cable Antenna Television | |
| 558. |
Thermal noise is independent of |
| A. | temperature |
| B. | bandwidth |
| C. | centre frequency |
| D. | Boltzmann constant |
| Answer» D. Boltzmann constant | |
| 559. |
A + 1.9 lens has a focal length of 25 mm. The diameter of lens is about |
| A. | 13 mm |
| B. | 1.3 mm |
| C. | 130 mm |
| D. | none of the above |
| Answer» B. 1.3 mm | |
| 560. |
In telephone, the dial tone has a frequency of |
| A. | 5 Hz |
| B. | 15 Hz |
| C. | 33 Hz |
| D. | 233 Hz |
| Answer» D. 233 Hz | |
| 561. |
1 GHz is equal to |
| A. | 106 Hz |
| B. | 108 Hz |
| C. | 109 Hz |
| D. | 1010 Hz |
| Answer» C. 109 Hz | |
| 562. |
Assertion (A): Electromagnetic waves in free space spread uniformly in all directions from a point sourceReason (R): Free space has no interference or obstacles. |
| 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 | |
| 563. |
The number of possible colours with a 4 line digital input monitor are |
| A. | 4 |
| B. | 16 |
| C. | 64 |
| D. | 2 |
| Answer» C. 64 | |
| 564. |
For signal amplitude modulated to a depth of 100% by a sinusoidal signal, power is |
| A. | same as that of unmodulated carrier |
| B. | twice the power of unmodulated carrier |
| C. | times the power of unmodulated carrier |
| D. | times the power of unmodulated carrier |
| Answer» D. times the power of unmodulated carrier | |
| 565. |
Commercial Frequency deviation of FM is |
| A. | 70 kHz |
| B. | 75 kHz |
| C. | 80 kHz |
| D. | 65 kHz |
| Answer» C. 80 kHz | |
| 566. |
In TV systems, equalising pulses are sent during |
| A. | horizontal blanking |
| B. | vertical blanking |
| C. | serrations |
| D. | horizontal retrace |
| Answer» B. vertical blanking | |
| 567. |
Consider the following statements as regards IF in radio receivers If IF is too high, poor selectivity and poor adjacent channel rejection could resultIf IF is high, tracking difficulties increaseA very low IF makes selectivity too sharpAs IF is decreased, image frequency rejection becomes better Which of the above are correct? |
| A. | 1, 2, 3, 4 |
| B. | 1, 2, 3 |
| C. | 2, 3, 4 |
| D. | 1, 3, 4 |
| Answer» C. 2, 3, 4 | |
| 568. |
A carrier is modulated by two modulating waves A and B having modulation indices of 0.6 and 0.8 respectively. The overall modulation index is |
| A. | 1 |
| B. | 0.7 |
| C. | 0.2 |
| D. | 1.4 |
| Answer» B. 0.7 | |
| 569. |
In single tone FM discriminator (S0/N0) is |
| A. | proportional to deviation |
| B. | proportional to cube of deviation |
| C. | proportional to square of deviation |
| D. | none of the above |
| Answer» E. | |
| 570. |
According to CCIR standards, the Vestigial Sideband (VSB) |
| A. | video frequencies upto 4 MHz are transmitted |
| B. | video frequencies upto 5 MHz are transmitted |
| C. | video frequencies upto 5.5 MHz are transmitted |
| D. | video frequencies upto 6 MHz are transmitted |
| Answer» C. video frequencies upto 5.5 MHz are transmitted | |
| 571. |
The effective length of antenna is different from actual length due to |
| A. | top loading |
| B. | end effects |
| C. | both (a) and (b) |
| D. | none of the above |
| Answer» D. none of the above | |
| 572. |
Which wave is also called surface wave? |
| A. | Ground wave |
| B. | Sky wave |
| C. | Space wave |
| D. | Both (b) and (c) |
| Answer» B. Sky wave | |
| 573. |
Which of the following is not true as regards communication receiver? |
| A. | It is exactly same as radio receiver used in households |
| B. | It can be used, besides communication, for detection in high frequency bridges |
| C. | It is designed to perform the task of low and high frequency reception better than in household receiver |
| D. | Its tuning and operation are more complicated than those in household receiver |
| Answer» B. It can be used, besides communication, for detection in high frequency bridges | |
| 574. |
In cell communication, cell stands for |
| A. | Geographical Area |
| B. | Battery |
| C. | Location |
| D. | No meaning |
| Answer» B. Battery | |
| 575. |
In FM, |
| A. | there is a large decrease in noise and hence increase in the signal to noise ratio |
| B. | there is a large increase in noise and hence decrease in the signal to noise ratio |
| C. | there is a large increase in noise and hence increase in the signal to noise ratio |
| D. | there is a large decrease in noise and hence decrease in the signal to noise ratio |
| Answer» B. there is a large increase in noise and hence decrease in the signal to noise ratio | |
| 576. |
Low frequency boost can be easily compensated by |
| A. | attenuating the frequencies from 0 to 1.25 MHz |
| B. | using an appropriate de-emphasis circuit in the receiver |
| C. | using an appropriate pre-emphasis circuit in the transmitter |
| D. | none |
| Answer» B. using an appropriate de-emphasis circuit in the receiver | |
| 577. |
The modulation index of a narrowband FM signal is |
| A. | nearly equal to 0.3 |
| B. | much less than unity |
| C. | nearly 0.5 |
| D. | much more than unity |
| Answer» B. much less than unity | |
| 578. |
The frequency response of a microphone means |
| A. | bandwidth of frequencies having output with in ± 1 dB of the output at 1000 Hz |
| B. | bandwidth of frequencies having output with in ± 3 dB of the output at 1000 Hz |
| C. | bandwidth of frequencies having output with in ± 1 dB of the output at 500 Hz |
| D. | bandwidth of frequencies having output with in ± 3 dB of the output at 500 Hz |
| Answer» B. bandwidth of frequencies having output with in ¬± 3 dB of the output at 1000 Hz | |
| 579. |
An RF carrier of 12 kV at 1 MHz is amplitude modulated by 1 kHz signal having peak value of 6 kV. The modulation pattern is seen on CRO screen. The voltage indicated will be |
| A. | 18 kV |
| B. | 1.001 kV |
| C. | 6 kV |
| D. | 36 kV |
| Answer» E. | |
| 580. |
Which of the following is used to generate PDM? |
| A. | Free running multi-vibrator |
| B. | Monostable multi-vibrator |
| C. | JK flip-flop |
| D. | Schmitt trigger |
| Answer» C. JK flip-flop | |
| 581. |
If sound wave has an intensity of 10 Pa. The dB level is about |
| A. | 1.139 dB |
| B. | 11.39 dB |
| C. | 113.9 dB |
| D. | 1139 dB |
| Answer» D. 1139 dB | |
| 582. |
A video transmission system transmits 625 picture frames per second. Each frame consist of a 400 x 400 pixel grid with 64 intensity levels per pixel. The data rate of the system is |
| A. | 600 Mbps |
| B. | 6.4 Gbps |
| C. | The system is basically phase, not frequency, modulation |
| D. | AFC is not needed, as a crystal oscillator is used |
| Answer» D. AFC is not needed, as a crystal oscillator is used | |
| 583. |
Quantization noise occurs in |
| A. | PAM |
| B. | DM |
| C. | PWM |
| D. | PPM |
| Answer» C. PWM | |
| 584. |
The contrast control in colour TV receiver is done by |
| A. | chroma amplifier |
| B. | SAW filter |
| C. | video detector |
| D. | luminance amplifier |
| Answer» E. | |
| 585. |
The tape recorders used in homes have |
| A. | common head and common amplifier system for recording and playback |
| B. | different heads and amplifiers for recording and playback |
| C. | same head but different amplifiers for recording and playback |
| D. | different heads but same amplifier for recording and playback |
| Answer» B. different heads and amplifiers for recording and playback | |
| 586. |
Satellite communication uses frequencies in the range of |
| A. | 3 to 6 GHz |
| B. | 3-10 MHZ |
| C. | 10-50 GHz |
| D. | 100-200 GHz |
| Answer» B. 3-10 MHZ | |
| 587. |
The noise sources shot noise, partition noise and thermal noise are associated with which component |
| A. | BJT |
| B. | diode |
| C. | resistor |
| D. | capacitor |
| Answer» B. diode | |
| 588. |
In FM, as bandwidth increases |
| A. | distortion increases |
| B. | distortion decreases |
| C. | distortion remains unaffected |
| D. | all |
| Answer» C. distortion remains unaffected | |
| 589. |
Three analog signals, having bandwidths 1200 Hz, 600 Hz, 600 Hz are sampled at their Nyquist rates, encoded with 12 bit words, and time division multiplexed. The bit rate for the multiplexed signal is |
| A. | 115.2 kbps |
| B. | 28.8 kbps |
| C. | 57.6 kbps |
| D. | 38.4 kbps |
| Answer» D. 38.4 kbps | |
| 590. |
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 | |
| 591. |
Assertion (A): Stubs, directional couplers and baluns are very commonly used in communication systemsReason (R): Characteristic impedance of a line is an important parameter. |
| 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 | |
| 592. |
The FM broadcast band is from |
| A. | 550 to 1600 kHz |
| B. | 88 to 108 kHz |
| C. | 88 to 108 MHz |
| D. | 1600 kHz to 59.75 MHz |
| Answer» D. 1600 kHz to 59.75 MHz | |
| 593. |
An amplifier has an input resistance of 10 kΩ and the noise voltage is 10 μV. If two such resistances of 10 kΩ each are connected in series at the input, the total noise voltage is about |
| A. | 20 μV |
| B. | 5μV |
| C. | 14.14 μV |
| D. | 10 μV |
| Answer» D. 10 ŒºV | |
| 594. |
A line has standing waves with a voltage maximum of 35 mV and minimum of 17.5 mV VSWR is |
| A. | 2 |
| B. | 4 |
| C. | 0.5 |
| D. | 0.25 |
| Answer» B. 4 | |
| 595. |
Which of the following noise sources is different from others? |
| A. | Cosmic |
| B. | Solar |
| C. | Atmospheric |
| D. | Galactic |
| Answer» D. Galactic | |
| 596. |
Homodyne detection means |
| A. | coherent detection |
| B. | non-coherent detection |
| C. | asynchronous detection |
| D. | none of the above |
| Answer» B. non-coherent detection | |
| 597. |
The autocorrelation function of the white noise is |
| A. | impulse function |
| B. | step function |
| C. | constant |
| D. | none of the above |
| Answer» D. none of the above | |
| 598. |
Which of the following stage is not present in AM receiver as compared to FM receiver? |
| A. | AM amplifier |
| B. | Demodulator |
| C. | Amplitude limiter |
| D. | AF amplitude |
| Answer» D. AF amplitude | |
| 599. |
The speeds used in recording audio programs in house hold recorders are |
| A. | 38 cm/s and 9.5 cm/s |
| B. | 38 cm/s and 19 cm/s |
| C. | 9.5 cm/s and 4.75 cm/s |
| D. | 38 cm/s and 4.75 cm/s |
| Answer» D. 38 cm/s and 4.75 cm/s | |
| 600. |
The number of bits of information required to indicate the correct selection of 3 independent consecutive events out of 75 equally probable events is |
| A. | 6.23 |
| B. | 18.69 |
| C. | 10.46 |
| D. | 24.92 |
| Answer» C. 10.46 | |