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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.
| 701. |
In high power radars, which of the following are used for switching? |
| A. | Power diode |
| B. | Power BJT |
| C. | Power MOSFET |
| D. | Thyristor |
| Answer» E. | |
| 702. |
Each frequency in the modulating wave gives rise to four side bands. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 703. |
A sinusoidal carrier voltage, having frequency 1000 Hz is amplitude modulated by a sinusoidal voltage of frequency 15 kHz. The frequency of upper and lower sidebands will be |
| A. | 1015 kHz and 985 kHz |
| B. | 1030 kHz and 970 kHz |
| C. | 13 kHz and 17 kHz |
| D. | 14 kHz and 16 kHz |
| Answer» E. | |
| 704. |
Which of the following is the disadvantage of PDM and PPM? |
| A. | It requires pulses of larger widths |
| B. | More samples are needed per second |
| C. | More powerful transmitter is required |
| D. | None of the above |
| Answer» D. None of the above | |
| 705. |
In tape recorders the hissing noise is due to irregularities in magnetic coating on tape. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 706. |
The intermediate frequency of a superheterodyne receiver is 450 kHz. If it is tuned to 1200 kHz, the image frequency will be |
| A. | 750 kHz |
| B. | 900 kHz |
| C. | 1600 kHz |
| D. | 2100 kHz |
| Answer» E. | |
| 707. |
The efficiency of a direct radiating cone type loudspeaker is about |
| A. | 0.05 |
| B. | 0.2 |
| C. | 0.5 |
| D. | 0.8 |
| Answer» B. 0.2 | |
| 708. |
If transmission path, in PCM, is very long then |
| A. | repeater stations are used |
| B. | pulse width may be increased |
| C. | pulse amplitude is increased |
| D. | pulse spacing is reduced |
| Answer» B. pulse width may be increased | |
| 709. |
The number of channels available in MF band (300 kHz - 3 MHz) for AM modulating signal of 20 kHz is |
| A. | 70 |
| B. | 67 |
| C. | 100 |
| D. | 150 |
| Answer» C. 100 | |
| 710. |
The maximum power output of a standard A earth station over the total band allocated to satellite communication is about |
| A. | 0.5 kW |
| B. | 8 kW |
| C. | 20 kW |
| D. | 50 kW |
| Answer» B. 8 kW | |
| 711. |
Assertion (A): Many times a radar cannot detect 'grounding hopping' military aircraft.Reason (R): Ground interference limits the range of radar. |
| 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 | |
| 712. |
Y signal has maximum percentage of |
| A. | red colour |
| B. | blue colour |
| C. | green colour |
| D. | red and blue colours |
| Answer» D. red and blue colours | |
| 713. |
Which of the following refers to SSB suppressed carrier amplitude modulated system? |
| A. | A3E |
| B. | H3E |
| C. | J3E |
| D. | C3F |
| Answer» D. C3F | |
| 714. |
When the number of quantising levels is 16 in PCM, the number of pulses in a code group will be |
| A. | 3 |
| B. | 4 |
| C. | 8 |
| D. | 16 |
| Answer» C. 8 | |
| 715. |
The main advantage of TDM over FDM is that it |
| A. | needs less power |
| B. | needs less bandwidth |
| C. | needs simple circuitry |
| D. | gives better S/N ratio |
| Answer» D. gives better S/N ratio | |
| 716. |
In FM, as the modulating frequency decreases and the modulating voltage amplitude |
| A. | increases, the modulation index increases |
| B. | decrease, the modulation index increases |
| C. | remains constant, the modulation index increases |
| D. | remains constant, the modulation index decreases |
| Answer» D. remains constant, the modulation index decreases | |
| 717. |
The total number of channels allotted for cellular telephone is |
| A. | 666 |
| B. | 333 |
| C. | 221 |
| D. | 111 |
| Answer» B. 333 | |
| 718. |
Vividh Bharti programme is transmitted in |
| A. | short wave |
| B. | medium frequency |
| C. | all of the above |
| D. | none of the above |
| Answer» D. none of the above | |
| 719. |
Figure shows the arrangement of |
| A. | FM |
| B. | PM |
| C. | AM-DSB |
| D. | AM-SSB |
| Answer» D. AM-SSB | |
| 720. |
Noise can be reduced by increasing sampling rate |
| A. | 1 |
| B. | |
| C. | can't say |
| D. | insufficient data |
| Answer» C. can't say | |
| 721. |
A three stage telephone switching structure is to have 128 input and 128 output terminals. There are 16 first stage and 16 third stage matrices. To avoid blocking the number of intermediate paths required is |
| A. | 16 |
| B. | 15 |
| C. | 8 |
| D. | 1 |
| Answer» C. 8 | |
| 722. |
In a TV receiver antenna the length of reflector rod |
| A. | is the same as that of dipole |
| B. | is less than that of dipole |
| C. | is more than that of dipole |
| D. | may be equal, more or less than that of dipole |
| Answer» D. may be equal, more or less than that of dipole | |
| 723. |
AGC voltage is applied to the stages which are |
| A. | before the detector stage |
| B. | after the detector stage |
| C. | either before or after the detector stage |
| D. | none of the above |
| Answer» B. after the detector stage | |
| 724. |
A fascimile reproduction has a specification of 200 lines per frame, progressive scanning and 5 frames per second. The time to scan one line is |
| A. | 5 ms |
| B. | 2.5 ms |
| C. | 1 ms |
| D. | 0.1 ms |
| Answer» D. 0.1 ms | |
| 725. |
What is the purpose of peak clipper circuits in radio transmitters? |
| A. | To prevent overmodulation |
| B. | To reduce bandwidth |
| C. | To increase bandwidth |
| D. | To regulate oscillator I/P voltage |
| Answer» B. To reduce bandwidth | |
| 726. |
Armstrong F.M. transmitter performs frequency multiplication in stages |
| A. | to increase the overall S/N |
| B. | for convenience |
| C. | to reduce the bandwidth |
| D. | to find the desired value of carrier frequency with frequency deviation |
| Answer» E. | |
| 727. |
Television transmission is by |
| A. | ground waves |
| B. | sky waves |
| C. | space waves |
| D. | all of the above |
| Answer» D. all of the above | |
| 728. |
For broadcasting purpose, full AM signal is preferred to SSB signal because |
| A. | it requires large bandwidth |
| B. | generation of full AM is easier |
| C. | detection of full AM is simpler |
| D. | none of the above |
| Answer» C. detection of full AM is simpler | |
| 729. |
AM transmitter employing low level modulation |
| A. | uses class C amplifier for amplification |
| B. | requires higher audio power |
| C. | has a poor efficiency |
| D. | has a higher efficiency |
| Answer» D. has a higher efficiency | |
| 730. |
Two messages m1, and m2 have a probability of 0.5 each. The entropy is |
| A. | 0.25 |
| B. | 0.5 |
| C. | 0.75 |
| D. | 1 |
| Answer» E. | |
| 731. |
In Vidicon camera tube, the resistance of photoconductive material on the target plate |
| A. | is constant |
| B. | is more in darkness and less in brightness |
| C. | is more in brightness but less in darkness and brightness |
| D. | may be more or less in darkness and brightness |
| Answer» C. is more in brightness but less in darkness and brightness | |
| 732. |
An oscillator at 4.2 MHz is followed by two frequency doublers and two triplers. The output frequency will be |
| A. | 84 MHz |
| B. | 112.4 MHz |
| C. | 151.2 MHz |
| D. | 303.4 MHz |
| Answer» D. 303.4 MHz | |
| 733. |
In a colour TV receiver, the sound intercarrier IF is generated in |
| A. | video detector |
| B. | video IF amplifier |
| C. | tuner mixer stage |
| D. | limiter stage |
| Answer» B. video IF amplifier | |
| 734. |
In a circuit the value of resistor is made four times. The noise voltage generated by this resistance will |
| A. | be doubled |
| B. | be increased four times |
| C. | remain the same |
| D. | become half |
| Answer» B. be increased four times | |
| 735. |
An AM wave is given by s(t)AM = 20 (1 + 0.5 cos 103t + 0.3 cos 104 t cos 106 t) the modulation index of the envelope is |
| A. | 0.5 |
| B. | 0.58 |
| C. | 0.3 |
| D. | 0.8 |
| Answer» C. 0.3 | |
| 736. |
If e = 10 sin(108 t + 3 sin 104 t) then modulating frequency is |
| A. | 159 Hz |
| B. | 1590 Hz |
| C. | 1.59 MHz |
| D. | 15.9 MHz |
| Answer» C. 1.59 MHz | |
| 737. |
In a radio detector |
| A. | stabilization against signal strength variation is provided |
| B. | linearity is worse than in a phase discriminator |
| C. | the circuit is the same as in discriminator except that diodes are reversed |
| D. | output is twice that obtainable from a similar phase discriminator |
| Answer» C. the circuit is the same as in discriminator except that diodes are reversed | |
| 738. |
In pulse code modulation when the maximum frequency in the signal is fmax the bandwidth required will be |
| A. | ≤ p.fmax |
| B. | ‚â• p.fmax |
| C. | ≤ (p.fmax)2 |
| D. | ‚â• (p.fmax)2 |
| Answer» C. ‚⧠(p.fmax)2 | |
| 739. |
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. | |
| 740. |
A planar array radar uses a high gain planar array antenna. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 741. |
A noise can be represented as superposition of spectral components. When this noise is passed through a narrow band filter, the output of filter should look like |
| A. | sinusoidal |
| B. | rectangular |
| C. | triangular |
| D. | none of the above |
| Answer» B. rectangular | |
| 742. |
PWM can be generated |
| A. | by a free running multivibrator |
| B. | by integrating the signal |
| C. | by a monostable multivibrator |
| D. | by differentiating pulse position modulation |
| Answer» D. by differentiating pulse position modulation | |
| 743. |
In a PCM the amplitude levels are transmitted in a 7 unit code. The no. of levels is |
| A. | 18 |
| B. | 14 |
| C. | 128 |
| D. | 64 |
| Answer» D. 64 | |
| 744. |
If transmitted power is 75 kW, the field strength at 30 km distance will be about |
| A. | 10 V/m |
| B. | 1 V/m |
| C. | 50 mV/m |
| D. | 2 mV/m |
| Answer» D. 2 mV/m | |
| 745. |
In a stereo tape recorder the speed of the tape is |
| A. | 38 m/s |
| B. | 19 m/s |
| C. | 9.5 m/s |
| D. | 4.75 m/s |
| Answer» E. | |
| 746. |
E and H fields are perpendicular to each other. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 747. |
When a wave reaches the open circuited end of a line |
| A. | all the forward energy is reflected by the open circuit |
| B. | all the forward energy is absorbed by the open circuit |
| C. | a small portion of energy is radiated into atmosphere and the remaining energy is reflected |
| D. | either (a) or (b) |
| Answer» D. either (a) or (b) | |
| 748. |
An FM signal with deviation δ is passed through mixer. Its frequency is reduced five fold. The deviation in output of mixer is |
| A. | 0.28 |
| B. | δ |
| C. | 5 δ |
| D. | very very high |
| Answer» C. 5 Œ¥ | |
| 749. |
Which of the following pulse-time modulation is least used? |
| A. | PDM |
| B. | PPM |
| C. | PWM |
| D. | PAM |
| Answer» E. | |
| 750. |
In PAL system weighting of R - Y and B - Y signals is done to |
| A. | prevent over modulation on saturated colours |
| B. | prevent under modulation of saturated colours |
| C. | allow over modulation of saturated colours |
| D. | allow under modulation on saturated colours |
| Answer» B. prevent under modulation of saturated colours | |