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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.
| 1001. |
The complete video signal consists of |
| A. | video signal and synchronising pulses |
| B. | video signal, synchronising pulses and blanking pulses |
| C. | video signal corresponding to picture information only |
| D. | video signal and blanking pulses |
| Answer» C. video signal corresponding to picture information only | |
| 1002. |
A device with input x(t) and y(t) is characterized by y(t) = x2(t). An FM signal with frequency deviation of 90 kHz and modulating signal bandwidth of 5 kHz is applied to this device. The bandwidth of the output signal is |
| A. | 370 kHz |
| B. | 190 kHz |
| C. | 380 kHz |
| D. | 95 kHz |
| Answer» D. 95 kHz | |
| 1003. |
Tracking of extra terrestrial objects requires |
| A. | high transmitting power |
| B. | very sensitive receiver |
| C. | fully steerable antenna |
| D. | all of the above |
| Answer» E. | |
| 1004. |
Some features of RF stage in good radio receivers is It increases sensitivity by providing amplification to RF signalIt eliminates image frequency interferenceIt increases selectivityIt reduces noise level Which of the above are true? |
| A. | 1, 2 and 3 only |
| B. | 1, 2 and 4 only |
| C. | 2, 3, 4 only |
| D. | 1, 2, 3, 4 |
| Answer» E. | |
| 1005. |
Audio cassettes used in household tape recorders have a width of |
| A. | 1" |
| B. | 1/2" |
| C. | 1/4" |
| D. | 1/8" |
| Answer» D. 1/8" | |
| 1006. |
In the television system in India, each frame is scanned |
| A. | 100 times |
| B. | 50 times |
| C. | 20 times |
| D. | 10 times |
| Answer» C. 20 times | |
| 1007. |
What is the RF amplifier plate voltage when the audio-modulating voltage is +600 V? |
| A. | -600 V |
| B. | Zero |
| C. | 600 V |
| D. | 1200 V |
| Answer» D. 1200 V | |
| 1008. |
In FM noise can be decreased by a feature that AM does not have |
| A. | increasing deviation |
| B. | decreasing deviation |
| C. | reducing modulation index |
| D. | increasing modulation index |
| Answer» D. increasing modulation index | |
| 1009. |
FSK is a system involving |
| A. | pulse modulation |
| B. | frequency modulation |
| C. | amplitude modulation |
| D. | phase modulation |
| Answer» C. amplitude modulation | |
| 1010. |
As the magnitude of reverse bias is increased, the capacitance of varactor diode |
| A. | increases |
| B. | decreases |
| C. | first increase, then decreases |
| D. | first decreases then increases |
| Answer» C. first increase, then decreases | |
| 1011. |
In a two tone AM system the two modulating frequencies are 2000 p and 4000 p rad/sec. If carrier frequency is 2p x 106 rad/sec the frequencies of upper sidebands are |
| A. | 1.002 MHz and 1.004 MHz |
| B. | 1.001 MHz and 1.002 MHz |
| C. | 1.001 MHz and 1.004 MHz |
| D. | 1.002 MHz and 1.008 MHz |
| Answer» C. 1.001 MHz and 1.004 MHz | |
| 1012. |
In FM signal with a modulation index mf is passed through a frequency tripler. The wave in the output of the tripler will have a modulation index of |
| A. | mf |
| B. | 3mf |
| C. | mf/3 |
| D. | mf/9 |
| Answer» C. mf/3 | |
| 1013. |
The phase of colour subcarrier burst in PAL is along the axis at |
| A. | +180° |
| B. | -180° |
| C. | ±180° |
| D. | ±45° |
| Answer» D. ¬±45¬∞ | |
| 1014. |
In PCM, bit duration is defined as |
| A. | |
| B. | |
| Answer» B. | |
| 1015. |
Consider the following statements about advantages of phase discriminator over slope detector Fewer tuned circuitsGreater limitingBetter linearityEasy alignment Which of the above are true? |
| A. | 1, 2, 3, 4 |
| B. | 2, 3, 4 |
| C. | 1, 2, 3 |
| D. | 1, 3, 4 |
| Answer» E. | |
| 1016. |
In cellular telephone each cell is designed to handle |
| A. | 45 two way communications |
| B. | 90 two way communications |
| C. | 45 one way communications |
| D. | 180 two way communications |
| Answer» B. 90 two way communications | |
| 1017. |
In pulse code modulation, if the signal is sampled at the rate of f and the number of pulses in one code group is p, then the number of pulses per second will be |
| A. | p/f |
| B. | f/p |
| C. | 1/pf |
| D. | pf |
| Answer» E. | |
| 1018. |
In an FM system, when the AF is 500 Hz and the AF voltage is 2.4 V, the deviation is 4.8 kHz. If the AF voltage is now increased to 7.2 V, the new deviation will be |
| A. | 4.8 kHz |
| B. | 9.6 kHz |
| C. | 14.4 kHz |
| D. | 28.8 kHz |
| Answer» D. 28.8 kHz | |
| 1019. |
Direct and reflected sound waves may interfere with each other. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 1020. |
Electronic tubes used for transmitter differ from their counterparts in the receivers in respect that |
| A. | they are large in size |
| B. | they are capable of handling large powers |
| C. | they generate large amount of heat when in operation |
| D. | none of the above |
| Answer» E. | |
| 1021. |
Which of the following is Doppler effect not used? |
| A. | CW radar |
| B. | FM radar |
| C. | MTI system |
| D. | Moving target plotting on PPI |
| Answer» E. | |
| 1022. |
A frequency doubler has an FM signal input at 13 MHz with a deviation of 5 kHz. The output, frequency for the carrier will be |
| A. | 26 MHz |
| B. | 26.1 MHz |
| C. | 10 kHz |
| D. | 160 kHz |
| Answer» E. | |
| 1023. |
A carrier is simultaneously modulated by two sine waves having modulation indices of 0.4 and 0.3. The total modulation index will be |
| A. | 0.1 |
| B. | 0.7 |
| C. | 0.5 |
| D. | 0.35 |
| Answer» D. 0.35 | |
| 1024. |
Which is most important subsystem for recovering and reconstructing signal in a TDM system? |
| A. | Envelope detector followed by a low pass filter |
| B. | Synchronization ckt for proper timing |
| C. | Bandpass filter to segregate channels |
| D. | Coherent detector to ensure frequency and phase connection |
| Answer» B. Synchronization ckt for proper timing | |
| 1025. |
Assertion (A): FM requires more bandwidth than AMReason (R): Wide band FM is used for broadcast transmissions. |
| 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 | |
| 1026. |
In a system using QASK and 4 bits to form a symbol, the required bandwidth is |
| A. | same as BPSK |
| B. | half of that in BPSK |
| C. | one-fourth of that in BPSK |
| D. | none of the above |
| Answer» D. none of the above | |
| 1027. |
High intermediate frequency in a superheterodyne receiver |
| A. | higher than |
| B. | lower than |
| C. | equal to |
| D. | not comparable to |
| Answer» B. lower than | |
| 1028. |
The type of noise that interfere very much with high frequency transmission is |
| A. | white |
| B. | transit time |
| C. | flicker |
| D. | shot |
| Answer» C. flicker | |
| 1029. |
If a line is terminated in characteristic impedance Z0, the input impedance measured at the input will be |
| A. | Z0 |
| B. | Z0/2 |
| C. | Zero |
| D. | infinite |
| Answer» B. Z0/2 | |
| 1030. |
Two sine waves of amplitude A1 and A2 are multiplied. The amplitude of the spectral component is |
| A. | |
| B. | A1A2 |
| Answer» B. A1A2 | |
| 1031. |
Which of the following cannot be the Fourier series expansion of a periodic signal? |
| A. | x(t) = 2 cos t + 3 cos 3t |
| B. | x(t) = 2 cos pt + 7 cos t |
| C. | x(t) = cos t + 0.5 |
| D. | x(t) = 2 cos 1.5pt + sin 3.5 pt |
| Answer» D. x(t) = 2 cos 1.5pt + sin 3.5 pt | |
| 1032. |
In MF range, increasing the transmitter power |
| A. | increases the range of transmitter |
| B. | does not increase the range of transmitter because propagation is limited by tilt |
| C. | decreases the range of transmitter because propagation is limited by tilt |
| D. | increases the range of transmitter because propagation is through space waves |
| Answer» C. decreases the range of transmitter because propagation is limited by tilt | |
| 1033. |
A pure tone at 1000 Hz has a dB level of 40 dB. If the required dB level is 100, the number of such tones is |
| A. | 2.5 |
| B. | 60 |
| C. | 104 |
| D. | 106 |
| Answer» E. | |
| 1034. |
In a reactance FET, gm = 9 x 10-3 Siemens, gate to source resistance is one-ninth of reactance of gate to drain capacitor and frequency is 4 MHz. The capacitive-reactance is |
| A. | 1000 Ω |
| B. | 1/1000 Ω |
| C. | 36 x 103 Ω |
| D. | x 103 Ω |
| Answer» B. 1/1000 Œ© | |
| 1035. |
Which camera tube has highest dark current? |
| A. | Plumbicon |
| B. | Vidicon |
| C. | Saticon |
| D. | GCD imager |
| Answer» B. Vidicon | |
| 1036. |
In a wave the electric field lines are vertical. Then the wave is |
| A. | horizontally polarized |
| B. | vertically polarized |
| C. | either (a) or (b) |
| D. | neither (a) nor (b) |
| Answer» C. either (a) or (b) | |
| 1037. |
Which of the following is correct (FDM means Frequency Division Multiplexing and TDM means Time Division Multiplexing)? |
| A. | FDM requires lower bandwidth but TDM has more noise immunity |
| B. | FDM has more noise immunity and requires lower bandwidth than TDM |
| C. | FDM requires channel synchronization while TDM has more noise immunity |
| D. | FDM requires more multiplexing while TDM requires band pass filter |
| Answer» D. FDM requires more multiplexing while TDM requires band pass filter | |
| 1038. |
Frequency shift keying is used mostly in |
| A. | telegraphy |
| B. | telephony |
| C. | satellite communication |
| D. | radio transmission |
| Answer» B. telephony | |
| 1039. |
Capture effect occurs in |
| A. | AM |
| B. | FM |
| C. | PCM |
| D. | QAM |
| Answer» C. PCM | |
| 1040. |
If k is dielectric constant of a medium, the velocity factor in that medium is |
| A. | 3 |
| B. | |
| Answer» C. | |
| 1041. |
Three point tracking is achieved with |
| A. | double conversion |
| B. | padder capacitor |
| C. | double spotting |
| D. | variable selectivity |
| Answer» C. double spotting | |
| 1042. |
Signal to noise ratio of microphone is defined as the ratio of output when the sound pressure is __________ to the output in the absence of any sound signal. |
| A. | 0.5 Pa |
| B. | 0.2 Pa |
| C. | 0.1 Pa |
| D. | 0.01 Pa |
| Answer» D. 0.01 Pa | |
| 1043. |
In transistor radio receivers the number of IF amplifier stages are |
| A. | 1 |
| B. | 2 |
| C. | 4 |
| D. | 6 |
| Answer» C. 4 | |
| 1044. |
Why does a FM radio station perform better than and AM station radiating the same actual power? |
| A. | FM is immune to noise |
| B. | AM has only two sidebands while FM has more |
| C. | FM uses larger bandwidth for large modulation depth. |
| D. | Capture effects appears in FM. |
| Answer» E. | |
| 1045. |
Consider the draw backs Slope overloadSerration noiseGranular noise Which of these draw backs does Delta modulation have? |
| A. | 1 and 2 only |
| B. | 2 and 3 only |
| C. | 1 and 3 only |
| D. | 1, 2, 3 |
| Answer» D. 1, 2, 3 | |
| 1046. |
The Shannon-Hartley law |
| A. | refers to noise |
| B. | defines bandwidth |
| C. | describes signalling rate |
| D. | refers to distortion |
| Answer» B. defines bandwidth | |
| 1047. |
A communication receiver is |
| A. | TRF receiver |
| B. | a superheterodyne receiver |
| C. | either (a) or (b) |
| D. | neither (a) nor (b) |
| Answer» C. either (a) or (b) | |
| 1048. |
Armstrong FM transmitter uses |
| A. | LC oscillator |
| B. | crystal oscillator |
| C. | RC oscillator |
| D. | either (a) or (c) |
| Answer» C. RC oscillator | |
| 1049. |
An antenna having a length of and grounded at one end is called |
| A. | Marconi antenna |
| B. | Yagi antenna |
| C. | Turnstile antenna |
| D. | None of the above |
| Answer» B. Yagi antenna | |
| 1050. |
The storage capacity of audio CD is 540 Mb per side. |
| A. | 1 |
| B. | |
| C. | class A |
| D. | class B |
| Answer» B. | |