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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.
| 501. |
The satellites used for intercontinental communication are called |
| A. | Comsat |
| B. | Domsat |
| C. | Marisat |
| D. | Intelsat |
| Answer» E. | |
| 502. |
The noise figure of individual stages of a two stage amplifier is 2.03 and 1.54 respectively. If gain of first stage is 62, the overall noise figure is |
| A. | 2.03 |
| B. | 2.055 |
| C. | 3.05 |
| D. | 6.05 |
| Answer» C. 3.05 | |
| 503. |
In case of a low level AM transmitter, the amplifier modulated stage must be |
| A. | class B (linear) |
| B. | class C |
| C. | class C audio amplifier |
| D. | tuned modulator |
| Answer» D. tuned modulator | |
| 504. |
An FM signal with a deviation δ is passed through a mixer, and has its frequency reduced 5 fold. The deviation in the output of the mixer is |
| A. | 5/δ |
| B. | Intermediate |
| C. | δ/5 |
| D. | δ |
| Answer» E. | |
| 505. |
In a single sideband suppressed carrier AM system, the modulation index is changed from 0 to 1, the power content of the signal |
| A. | will be quarter |
| B. | will be doubled |
| C. | will increase by 50 percent |
| D. | will increase by 25 percent |
| Answer» D. will increase by 25 percent | |
| 506. |
An audio signal (say from 50 Hz to 10000 Hz) is frequency translated by a carrier having a frequency of 106 Hz. The values of initial (without frequency translation) and final (after frequency translation) fractional change in frequency from one band edge to the other are |
| A. | 200 and 1.01 |
| B. | 200 and 10.01 |
| C. | 200 and 100.1 |
| D. | 200 and 200 |
| Answer» B. 200 and 10.01 | |
| 507. |
In the above case if another sine wave corresponding to 40% modulation is transmitted simultaneously, the total radiated power will be |
| A. | 9.9 kW |
| B. | 10.15 kW |
| C. | 10.84 kW |
| D. | 18.4 kW |
| Answer» D. 18.4 kW | |
| 508. |
The power required to produce a gain of 10 dB over 4 W of original power is __________ watt. |
| A. | 80 |
| B. | 40 |
| C. | 0.4 |
| D. | 8 |
| Answer» D. 8 | |
| 509. |
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 | |
| 510. |
A source has two symbols x1 and x2 with probabilities pi and pr. If a new source with four symbols is generated from the above source, the new symbol probabilities will be (‚àà is a number such that 0 < ‚àà < 1) |
| A. | p1, p2, p1, p2 |
| B. | p1, p1, p2, p2 |
| C. | (1 - ‚àà)p1, (1 - ‚àà) p2, p1, p2 |
| Answer» D. | |
| 511. |
PAL system was proposed first in |
| A. | USA |
| B. | Japan |
| C. | England |
| D. | Germany |
| Answer» E. | |
| 512. |
SWR for a transmission line is infinity when the load is Short circuitComplex impedanceOpen circuitPure reactance Of the above statements: |
| A. | 1, 3, 4 are correct |
| B. | 1 and 3 are correct |
| C. | 2, 3, 4 are correct |
| D. | 1, 2, 4 are correct |
| Answer» C. 2, 3, 4 are correct | |
| 513. |
In a FM receiver, amplitude limiter |
| A. | amplifiers low frequency signals |
| B. | reduces the amplitude of signals |
| C. | eliminates any change in amplitude of received FM signals |
| D. | none of the above |
| Answer» D. none of the above | |
| 514. |
Fourier series expansion of a real periodic signal with fundamental frequency is given by It is given that c3 = 3 + j5. then c-3 is |
| A. | 5 + j3 |
| B. | #VALUE! |
| C. | #REF! |
| D. | 3 - j5 |
| Answer» E. | |
| 515. |
The start of modern computer age was started by the event |
| A. | development of disc drive |
| B. | development of transistor |
| C. | development of Hollerith code |
| D. | design of EVIAC computer |
| Answer» C. development of Hollerith code | |
| 516. |
Industrial noise has the frequency range of |
| A. | 1 to 100 Hz |
| B. | 200 to 5000 Hz |
| C. | above 200 MHz |
| D. | 1 to 600 MHz |
| Answer» E. | |
| 517. |
A balun transformer gives an impedance transformation of |
| A. | 0.16736111111111 |
| B. | 0.084027777777778 |
| C. | 0.044444444444444 |
| D. | 0.043055555555556 |
| Answer» B. 0.084027777777778 | |
| 518. |
Which camera tube has gamma of almost unity? |
| A. | Vidicon |
| B. | Plumbicon |
| C. | New vicon |
| D. | Saticon |
| Answer» E. | |
| 519. |
CW Doppler radar is capable of giving accurate measurements of relative velocities. |
| A. | 1 |
| B. | |
| C. | the discriminator must have a fast time constant to prevent demodulation |
| D. | the higher discriminator frequency the better the oscillator frequency stability |
| Answer» B. | |
| 520. |
A direct radiating cone type loudspeaker attenuates : |
| A. | medium range frequencies |
| B. | very low frequencies |
| C. | high frequencies |
| D. | very low and high frequencies |
| Answer» E. | |
| 521. |
Radiation resistance of an antenna is a |
| A. | dc resistance |
| B. | ac resistance |
| C. | either (a) or (b) |
| D. | none of the above |
| Answer» C. either (a) or (b) | |
| 522. |
If carrier modulated by a digital bit stream had one of the possible phases of 0°, 90°, 180°, 270°, then the modulation is called. |
| A. | BPSK |
| B. | QPSK |
| C. | QAM |
| D. | MSK |
| Answer» C. QAM | |
| 523. |
The main systems used for generation of SSB are |
| A. | filter method |
| B. | phase cancellation method |
| C. | third method |
| D. | all of the above |
| Answer» E. | |
| 524. |
In the equation of M-ary PSK signal (where Ey is symbol energy), M becomes large. Then d will approach |
| A. | 2 |
| B. | infinity |
| C. | zero |
| D. | 1 |
| Answer» D. 1 | |
| 525. |
Consider the following statements in amplitude modulation The harmonic and intermodulation distortion may occur in audio and RF amplifiersThe sum and difference frequencies are present in the output of mixerThe diode detector has audio frequencies in its outputA balanced modulator cannot produce an AM with suppressed carrier Which of the above are true? |
| A. | 1, 2, 3, 4 |
| B. | 1, 2, 3 |
| C. | 1, 2 |
| D. | 3, 4 |
| Answer» C. 1, 2 | |
| 526. |
An FM wave is made to pass through a frequency tripler. If original modulation index is mf, the output of tripler has a modulation index equal to |
| A. | mf |
| B. | mf |
| C. | 3 mf |
| D. | mf |
| Answer» D. mf | |
| 527. |
If the carrier of a 100 percent modulated AM wave is suppressed, the percentage power saving will be |
| A. | 50 |
| B. | |
| C. | 100 |
| Answer» B. | |
| 528. |
In a radio receiver the input from local oscillator is fed to |
| A. | RF amplifier |
| B. | mixer |
| C. | IF amplifier |
| D. | detector |
| Answer» C. IF amplifier | |
| 529. |
Which of the following microphones works on the piezoelectric effect? |
| A. | Carbon |
| B. | Condenser |
| C. | Moving coil |
| D. | Crystal |
| Answer» E. | |
| 530. |
One of the advantages of base modulation over collector modulation in a class C transistor amplifier is |
| A. | higher efficiency |
| B. | more linear operation |
| C. | more power output per transistor |
| D. | lesser requirement of modulating power |
| Answer» E. | |
| 531. |
In a high speed modem the data rate handled is about |
| A. | 1000 bps |
| B. | 5000 bps |
| C. | 20000 bps |
| D. | 50000 bps |
| Answer» C. 20000 bps | |
| 532. |
Costa's receiver is used for |
| A. | coherent detection of AM-SC signal |
| B. | asynchronous detection of AM-SC signal |
| C. | amplitude modulation of signal |
| D. | frequency modulation of signal |
| Answer» B. asynchronous detection of AM-SC signal | |
| 533. |
In a tape recorder the erase head is |
| A. | engaged during playback but disengaged during recording |
| B. | engaged both during recording and playback |
| C. | disengaged both during recording and playback |
| D. | engaged during recording but disengaged during playback |
| Answer» E. | |
| 534. |
Which of the following codes provides parity checks? |
| A. | CCITT-2 |
| B. | EBCDIC |
| C. | ASCII |
| D. | Baudot |
| Answer» D. Baudot | |
| 535. |
The IF frequencies in a TV receiver |
| A. | 38.9 MHz for video and 33.4 MHz for audio |
| B. | 38.9 MHz for both video and audio |
| C. | 33.4 MHz for both video and audio |
| D. | 33.4 MHz for video and 38.9 MHz for audio |
| Answer» B. 38.9 MHz for both video and audio | |
| 536. |
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 | |
| 537. |
The constellation diagram of a modem has four states as shown in the figure given below. What is the bit rate of this modem? |
| A. | Two times its band rate |
| B. | Four times its band rate |
| C. | Same as band rate |
| D. | Sufficient information is not given to give the answer |
| Answer» B. Four times its band rate | |
| 538. |
Narrowband FM signal can be considered to be equal to |
| A. | PM |
| B. | AM |
| C. | SSB |
| D. | DSB |
| Answer» C. SSB | |
| 539. |
A 360 W carrier is simultaneously modulated by two audio wave with modulation percentage of 55 and 65 respectively. Total sideband power radiated will be |
| A. | 500 W |
| B. | 360 W |
| C. | 180 W |
| D. | 130 W |
| Answer» E. | |
| 540. |
Pulse modulation is used in |
| A. | radio navigation |
| B. | automatic landing equipment |
| C. | data communications |
| D. | all of the above |
| Answer» E. | |
| 541. |
In practical commercial FM system, channel bandwidth is |
| A. | 88 MHz |
| B. | 108 MHz |
| C. | is always vertical in an isotropic medium |
| D. | is caused by reflection |
| Answer» B. 108 MHz | |
| 542. |
Consider the following statements: The radar pulse must be flat topped to allow accurate range measurementallow good minimum rangeprevent frequency changes in magnetronmake the returned echoes easier to distinguish from noise. Which of the above are correct? |
| A. | 1, 2, 3, 4 |
| B. | 1, 2, 3 |
| C. | 1, 2 |
| D. | 1, 3, 4 |
| Answer» C. 1, 2 | |
| 543. |
In a DM system, the granular noise occurs when modulating signal |
| A. | decrease Rapidly |
| B. | increase |
| C. | has high frequency component |
| D. | change within step size |
| Answer» D. change within step size | |
| 544. |
Noise which assumes great importance at high frequencies is |
| A. | flicker noise |
| B. | Johnson noise |
| C. | transit-time noise |
| D. | shot noise |
| Answer» D. shot noise | |
| 545. |
Strength of space wave is not dependent on distance. |
| A. | 1 |
| B. | |
| C. | The signal is more noise resistant |
| D. | More channel space is available |
| Answer» B. | |
| 546. |
The radio receivers mostly used now a days are |
| A. | TRF receivers |
| B. | super heterodyne receivers |
| C. | CW receivers |
| D. | pulsed receivers |
| Answer» C. CW receivers | |
| 547. |
The number of spectral component of impulse wave is |
| A. | 1 |
| B. | 0 |
| C. | 2 |
| D. | ‚àû |
| Answer» E. | |
| 548. |
An MTI radar operating at 5 GHz has a PRF of 800 pps. The lowest blind speed is |
| A. | 48 m/s |
| B. | 96 m/s |
| C. | 192 m/s |
| D. | 24 m/s |
| Answer» B. 96 m/s | |
| 549. |
A ground wave travels along surface of ground. |
| A. | 1 |
| B. | |
| C. | near unity |
| D. | about 100 |
| Answer» B. | |
| 550. |
If fh(t) is the Hilbert transform of f(t), and f(t) is a real valued signal, the pre-envelope of f(t) is |
| A. | f(t) - jfh(t) |
| B. | f(t) + jfh(t) |
| C. | fh(t) + jf(t) |
| D. | fh(t) - jf(t) |
| Answer» C. fh(t) + jf(t) | |