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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.
| 851. |
In a 50 cm TV tube, a path difference of 2 km between direct wave and interfering wave would mean a displacement between main image and ghost image equal to |
| A. | 0.3 cm |
| B. | 3 cm |
| C. | 6 cm |
| D. | 9 cm |
| Answer» B. 3 cm | |
| 852. |
To eliminate ghosts in the picture |
| A. | use a longer transmission line |
| B. | connect a booster |
| C. | change the antenna orientation of location |
| D. | twist the transmission line |
| Answer» D. twist the transmission line | |
| 853. |
For F2 layer the critical frequency is about |
| A. | 500 MHz |
| B. | 100 MHz |
| C. | 25 MHz |
| D. | 10 MHz |
| Answer» E. | |
| 854. |
Coupling and bypass filters can be a source of |
| A. | low-frequency parasitics |
| B. | high-frequency parasitics |
| C. | carrier frequency parasitics |
| D. | none of the above |
| Answer» C. carrier frequency parasitics | |
| 855. |
Under ordinary circumstances, impulse noise can be reduced in |
| A. | FM only |
| B. | AM only |
| C. | both AM and FM |
| D. | none of the above |
| Answer» B. AM only | |
| 856. |
The maximum permissible distance between two samples of a 10 kHz signal |
| A. | 100 μ sec |
| B. | 50 μ sec |
| C. | 10 μ sec |
| D. | none |
| Answer» C. 10 Œº sec | |
| 857. |
Some desirable features of a computer communication network are It should accept an intended transmission without excessive delayThe data arriving at a receiving point should be processed rapidlyWhen a transmission calls for a response, the delay of response should be minimum. Which of the above are true? |
| A. | 1 and 2 only |
| B. | 1 and 3 only |
| C. | 1, 2, 3 |
| D. | 2 and 3 only |
| Answer» D. 2 and 3 only | |
| 858. |
If M (jω) = £[m(t)] where £ denotes Fourier transform, then £[m(t) cos ωct] = |
| A. | M (jω + jωc) |
| B. | M (jω - jωc) |
| C. | M (jω + jωc) + M (jω - jωc) |
| D. | [M (jω + jωc) + M (jω - jωc)] |
| Answer» E. | |
| 859. |
In amplitude modulation |
| A. | the amplitude of carrier varies in accordance with the amplitude of the modulating signal |
| B. | the modulating frequency lies in the audio range |
| C. | the amplitude of the carrier remains constant |
| D. | the amplitude of the carrier varies in accordance with the frequency of the modulating signal |
| Answer» B. the modulating frequency lies in the audio range | |
| 860. |
A TV receiver has a width of 60 cm. The aspect ratio is 4/3. The required EHT supply is about |
| A. | 29 kV |
| B. | 2.9 kV |
| C. | 45 kV |
| D. | 4.5 kV |
| Answer» B. 2.9 kV | |
| 861. |
A 200 Hz sound wave is to be transmitted by a 1000 kHz radio wave using frequency modulation. The instantaneous frequency variation will be |
| A. | 100 times a second |
| B. | 200 times a second |
| C. | 400 times a second |
| D. | 1000 times a second |
| Answer» C. 400 times a second | |
| 862. |
The power to the base unit of a cordless telephone is supplied by |
| A. | battery |
| B. | AC mains |
| C. | both battery and AC mains |
| D. | either battery or AC mains |
| Answer» C. both battery and AC mains | |
| 863. |
Short circuited stubs are preferred to O.C stubs because |
| A. | O.C stubs are incapable of giving full range of reactances |
| B. | O.C stubs are liable to radiate |
| C. | O.C stubs are difficult to make and connect |
| D. | none of the above |
| Answer» C. O.C stubs are difficult to make and connect | |
| 864. |
In grid bias modulation system the power required for modulating amplifier |
| A. | is negligibly low since grid is negative |
| B. | is large as compared to that for plate modulation |
| C. | is almost the same as compared with plate modulation |
| D. | is small as compared to that for plate modulation |
| Answer» E. | |
| 865. |
Modulation index of a AM wave is measured using oscilloscope. The display on the CRO is as shown in figure it can be concluded that |
| A. | the output wave is distorted |
| B. | the output wave is under modulated |
| C. | the modulation index is 100% |
| D. | the modulation index is 50% |
| Answer» B. the output wave is under modulated | |
| 866. |
The bandwidth of FM for Commercial Purpose is |
| A. | 88 - 108 MHz |
| B. | 85 - 110 MHz |
| C. | 90 - 110 MHz |
| D. | infinite Range |
| Answer» B. 85 - 110 MHz | |
| 867. |
In radio receivers, the value of IF is |
| A. | 100 kHz |
| B. | 225 kHz |
| C. | 455 kHz |
| D. | 850 kHz |
| Answer» D. 850 kHz | |
| 868. |
A frequency multiplier stage should operate as |
| A. | class A |
| B. | class B |
| C. | class AB |
| D. | class C |
| Answer» C. class AB | |
| 869. |
The carrier frequency will be if L = 50 µH and C = 1 nF. |
| A. | 512 |
| B. | 612 kHz |
| C. | 712 kHz |
| D. | 812 kHz |
| Answer» D. 812 kHz | |
| 870. |
The width of air gap on recording head in a tape recorder is about |
| A. | 6 micron |
| B. | 3 micron |
| C. | 1 micron |
| D. | 25 micron |
| Answer» B. 3 micron | |
| 871. |
The frequency range of 300 kHz to 3000 kHz is known as |
| A. | low frequency |
| B. | medium frequency |
| C. | high frequency |
| D. | very high frequency |
| Answer» C. high frequency | |
| 872. |
In binary data transmission DPSK is preferred to PSK because |
| A. | a coherent carrier is not required to the generated at the receiver |
| B. | for a given energy per bit, the probability for zero is less |
| C. | the 180° phase shifts of the carrier |
| D. | more protection is provided against impulse noise |
| Answer» B. for a given energy per bit, the probability for zero is less | |
| 873. |
Consider the following statements In a pulsed radar, the transmitted pulses are of high frequencyIn a pulsed radar, the transmitted pulses are of high powerIn a pulsed radar, the transmitted pulses are of brief durationIn a pulsed radar, the transmitted pulses are of square wave shape. Of the above statements the correct statements are |
| A. | 1 only |
| B. | 1, 2 and 3 only |
| C. | 1, 2, 3, 4 |
| D. | 1 and 3 only |
| Answer» C. 1, 2, 3, 4 | |
| 874. |
Graphic equaliser system in stereophonic systems generally have |
| A. | 3 or 4 bands |
| B. | 1 band |
| C. | more than 8 bands |
| D. | large number of bands |
| Answer» B. 1 band | |
| 875. |
Leak type bias is used in a plate-modulated class C amplifier to |
| A. | prevent tuned circuit damping |
| B. | prevent over modulation |
| C. | increase the bandwidth |
| D. | prevent excessive grid current |
| Answer» C. increase the bandwidth | |
| 876. |
The input to a coherent detector is DSB - SC signal plus noise. The noise at the detector output is |
| A. | in phase component |
| B. | quadrature component |
| C. | zero |
| D. | the envelope |
| Answer» B. quadrature component | |
| 877. |
An FM signal has modulating frequency fm and maximum frequency deviation of δ. The bandwidth will be nearly equal to |
| A. | δ |
| B. | 2 δ |
| C. | 2fm δ |
| D. | fm δ |
| Answer» C. 2fm Œ¥ | |
| 878. |
Which of the following is a better recording medium? |
| A. | Ferric oxide |
| B. | Ferrous oxide |
| C. | Chromium di oxide |
| D. | Either (a) or (b) |
| Answer» D. Either (a) or (b) | |
| 879. |
Sound wave travels as |
| A. | longitudinal waves |
| B. | transverse waves |
| C. | both longitudinal and transverse waves |
| D. | either longitudinal or transverse wave |
| Answer» E. | |
| 880. |
The modulation index of an FM is changed from 0 to 1. How does the transmitted power change? |
| A. | Gets halved |
| B. | Gets doubled |
| C. | Gets increased by 50 percent |
| D. | Remains unchanged |
| Answer» D. Remains unchanged | |
| 881. |
Skin depth at 1000 MHz in comparison with that at 500 MHz is |
| A. | 2 |
| B. | 2 |
| C. | |
| Answer» D. | |
| 882. |
In a superheterodyne radio receiver |
| A. | RF amplifier normally operates at 455 kHz above carrier frequency |
| B. | mixer input must be tuned to the signal frequency |
| C. | local oscillator operates below signal frequency |
| D. | local oscillator frequency is double the IF |
| Answer» C. local oscillator operates below signal frequency | |
| 883. |
In Pulse Code Modulation system |
| A. | large bandwidth is required |
| B. | quantising noise can be overcome by companding |
| C. | quantising noise can be reduced by decreasing the number of standard levels |
| D. | suffers from the disadvantage of its incompatibly with TDM |
| Answer» B. quantising noise can be overcome by companding | |
| 884. |
In cable TV local programmes can be telecast at any frequency. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 885. |
A wave is frequency modulated with an index of 0.1 and its frequency is multiplied by 8 times, the modulation index is |
| A. | not changed |
| B. | decreased 8 times |
| C. | increased 4 times |
| D. | increased 8 times |
| Answer» B. decreased 8 times | |
| 886. |
The filter circuit for feeding a wooffer has |
| A. | an inductance in series and capacitance in parallel |
| B. | a capacitance in series and an inductance in parallel |
| C. | a resistance in series and an inductance in parallel |
| D. | an inductance in series and a resistance in parallel |
| Answer» B. a capacitance in series and an inductance in parallel | |
| 887. |
The requirements of carrier frequency are |
| A. | precise frequency value |
| B. | low frequency drift |
| C. | both (a) and (b) |
| D. | neither (a) nor (b) |
| Answer» D. neither (a) nor (b) | |
| 888. |
Which of the following is likely to be associated with FM radio broadcasting? |
| A. | 90 Hz |
| B. | 90 kHz |
| C. | 900 kHz |
| D. | 90 MHz |
| Answer» E. | |
| 889. |
In VHS format diameter of head drum is about |
| A. | 1 m |
| B. | 20 cm |
| C. | 6 cm |
| D. | 1 cm |
| Answer» D. 1 cm | |
| 890. |
In the stabilized reactance modulator AFC system |
| A. | phase modulation is converted into amplitude modulation by the equalizer circuit |
| B. | the discriminator frequency must not be too low or the system will fail |
| C. | the discriminator must have a fast time constant to prevent demodulation |
| D. | the higher discriminator frequency, better the oscillator frequency stability |
| Answer» C. the discriminator must have a fast time constant to prevent demodulation | |
| 891. |
The most commonly used system of modulating for telegraphy is |
| A. | single tone modulation |
| B. | on-off keying |
| C. | frequency shift keying |
| D. | pulse code modulation |
| Answer» D. pulse code modulation | |
| 892. |
The bandwidth required for amplitude modulation is |
| A. | half the frequency of modulating signal |
| B. | equal to the frequency of modulating signal |
| C. | twice the frequency of modulating signal |
| D. | four times the frequency of modulating signal |
| Answer» D. four times the frequency of modulating signal | |
| 893. |
In PCM, if the number of quantization levels is increased from 4 to 64, then the bandwidth requirement will approximately be increased __________ times. |
| A. | 8 |
| B. | 16 |
| C. | 3 |
| D. | 32 |
| Answer» D. 32 | |
| 894. |
In ionosphere incidence angle is 60°. The maximum usable frequency fm is equal to |
| A. | 2fc |
| B. | fc |
| C. | 0.5 fc |
| D. | 3 fc |
| Answer» B. fc | |
| 895. |
In case of frequency modulation, modulating voltage remains constant if the modulating frequency is lowered, then |
| A. | amplitude of distant sidebands decreases |
| B. | amplitude of distant sidebands increases |
| C. | amplitude of distant sidebands remains constant |
| D. | amplitude of distant sidebands first increases, then decreases |
| Answer» C. amplitude of distant sidebands remains constant | |
| 896. |
In spread spectrum technique |
| A. | a modulated signal is modulated again |
| B. | a modulated signal is modulated twice again |
| C. | the power of a modulated signal is increased |
| D. | the noise component of a modulated signal is decreased |
| Answer» E. | |
| 897. |
The different channels in a TDM receiver are separated by |
| A. | integration |
| B. | differentiation |
| C. | AND gate |
| D. | OR gate |
| Answer» D. OR gate | |
| 898. |
If output power of a radio receiver is doubled, its volume is increased by __________ dB. |
| A. | 2 |
| B. | 3 |
| C. | 1 |
| D. | -3 |
| Answer» C. 1 | |
| 899. |
Top loading in an antenna increases |
| A. | effective height |
| B. | beam width |
| C. | input capacitance |
| D. | bandwidth |
| Answer» B. beam width | |
| 900. |
The primary colours are |
| A. | blue and green |
| B. | blue and red |
| C. | red and green |
| D. | blue, red and green |
| Answer» E. | |