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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.
| 901. |
The percentage saving in power of 100% modulated suppressed carrier AM signal is |
| A. | 100 |
| B. | 75 |
| C. | 66.6 |
| D. | 50 |
| Answer» D. 50 | |
| 902. |
A TV receiver has 20 kV EHT supply and total beam current (for 3 electron guns) of 1500 μA. The power handled by IHVT is |
| A. | 3 W |
| B. | 30 W |
| C. | 300 W |
| D. | 0.3 W |
| Answer» C. 300 W | |
| 903. |
The simplest method of suppression of unwanted side band in AM is |
| A. | filter method |
| B. | phase shift method |
| C. | third method |
| D. | both (a) and (b) |
| Answer» B. phase shift method | |
| 904. |
Which of the following is not necessarily the advantage of SSB over double sideband, full carrier AM? |
| A. | The signal is more noise resistant |
| B. | More channel space is available |
| C. | Transmitter circuits must be more stable, given better reception |
| D. | Considerably less power is required for the same signal strength |
| Answer» D. Considerably less power is required for the same signal strength | |
| 905. |
The spectrum of the white noise and an impulse function is similar in following aspects |
| A. | both have similar magnitude spectrum |
| B. | both have similar magnitude and Phase spectrum |
| C. | no relation |
| D. | similar phase spectrum |
| Answer» B. both have similar magnitude and Phase spectrum | |
| 906. |
Under identical conditions, for a single modulating frequency, FM and PM are indistinguishable. Now if the modulating frequency is reduced, then |
| A. | phase modulation index as well as frequency modulation index decrease |
| B. | phase modulation index as well as frequency modulation index increase |
| C. | phase modulation index will remain constant whereas frequency modulation index will increase |
| D. | phase modulation index will decrease whereas frequency modulation index will remain constant |
| Answer» D. phase modulation index will decrease whereas frequency modulation index will remain constant | |
| 907. |
The modulating frequency in frequency modulation is increased from 10 kHz to 30 kHz. The bandwidth is increased by |
| A. | 6 |
| B. | 1/6 times |
| C. | increase by 30 kHz |
| D. | increase by 20 kHz |
| Answer» B. 1/6 times | |
| 908. |
Pressing a key on telephone set generates two frequencies. The basis for selection of these frequencies is |
| A. | the harmonics of one frequency should not be mistaken for the other frequency |
| B. | the audio input to the handset transmitter should not be mistaken for a key pressing |
| C. | both (a) and (b) |
| D. | neither (a) nor (b) |
| Answer» D. neither (a) nor (b) | |
| 909. |
Armoured submarine cable is used |
| A. | to prevent insulation breakdown due to high voltage |
| B. | to protect cable at great depths. |
| C. | to prevent inadverent damage due to ploughing in |
| D. | for the shallow shore ends of cable. |
| Answer» E. | |
| 910. |
The frequency tolerance for the RF carrier in the standard AM radio broadcast band is |
| A. | zero |
| B. | +20 Hz |
| C. | +1000 Hz |
| D. | +25 Hz |
| Answer» B. +20 Hz | |
| 911. |
A broadcast radio transmitter radiates 5 kW when the modulation percentage is 60. How much of this is carrier power? |
| A. | 6.66 kW |
| B. | 5 kW |
| C. | 4.9 kW |
| D. | 4.23 kW |
| Answer» E. | |
| 912. |
The assigned carrier frequency of an FM broadcast station is 96.3 MHz. Its FM signal has a centre frequency of |
| A. | 10 MHz |
| B. | 455 kHz |
| C. | 48.15 MHz |
| D. | 96.3 MHz |
| Answer» E. | |
| 913. |
A remote control for TV uses |
| A. | LED in receiver and photodiode in transmitter |
| B. | LED in transmitter and photodiode in receiver |
| C. | LED in both transmitter and receiver |
| D. | Photodiode in both transmitter and receiver |
| Answer» C. LED in both transmitter and receiver | |
| 914. |
Good frequency stability can be available |
| A. | crystal oscillators |
| B. | Hartley oscillators |
| C. | colpitts oscillators |
| D. | none of the above |
| Answer» B. Hartley oscillators | |
| 915. |
In a low level AM system, the modulated amplifiers stage must be |
| A. | harmonic devices |
| B. | non-linear devices |
| C. | class C amplifier |
| D. | linear devices |
| Answer» E. | |
| 916. |
Entropies associated with an extremely unlikely message and that with an extremely likely message are respectively |
| A. | 0 and 0 |
| B. | 1 and 1 |
| C. | 1 and 0 |
| D. | 0 and 1 |
| Answer» B. 1 and 1 | |
| 917. |
In a low level AM system, the amplifier which follows the modulated stage must be the |
| A. | linear device |
| B. | harmonic device |
| C. | class C amplifier |
| D. | non-linear device |
| Answer» B. harmonic device | |
| 918. |
The currents fed to the two dipoles of turnstile antenna are |
| A. | in phase |
| B. | in quadrature |
| C. | in phase opposition |
| D. | either (a) or (c) |
| Answer» C. in phase opposition | |
| 919. |
In a Vidicon camera tube |
| A. | grid G1 accelerates electrons |
| B. | grid G2 accelerates electrons and grid G3, slows down electrons |
| C. | grid G3 accelerates electrons and grid G2 slows down electrons |
| D. | both grids G2 and G3 accelerate electrons |
| Answer» C. grid G3 accelerates electrons and grid G2 slows down electrons | |
| 920. |
Which one of the following is an indirect way of generating FM? |
| A. | Armstrong modulator |
| B. | Varactor diode modulator |
| C. | Reactance FET modulator |
| D. | Reactance bipolar transistor modulator |
| Answer» B. Varactor diode modulator | |
| 921. |
Point out the false statement |
| A. | impulse noise voltage does not depend on bandwidth |
| B. | thermal noise is independent of frequency at which it is measured |
| C. | industrial noise is mostly of impulse type |
| D. | space noise is observable at frequencies in the range of 8 MHz and higher |
| Answer» B. thermal noise is independent of frequency at which it is measured | |
| 922. |
PA radar means |
| A. | Phased Array radar |
| B. | Pulsed Array radar |
| C. | Pulse Amplitude radar |
| D. | None of the above |
| Answer» B. Pulsed Array radar | |
| 923. |
The most suitable method for detecting a modulated signal g(t) = (3 to 6 cos 2pfmt) cos 2pfct is |
| A. | envelope detector |
| B. | synchronous detector |
| C. | ratio detector |
| D. | both a and b |
| Answer» B. synchronous detector | |
| 924. |
A pulse width signal can be governed by |
| A. | free running multi-vibrator |
| B. | monostable multi-vibrator |
| C. | Schmitt trigger |
| D. | JK flip-flop |
| Answer» C. Schmitt trigger | |
| 925. |
An amplifier of passband 450 kHz to 460 kHz will be named as |
| A. | video amplifier |
| B. | audio frequency amplifier |
| C. | tuned voltage amplifier |
| D. | wideband amplifier |
| Answer» D. wideband amplifier | |
| 926. |
Cross talk is due to reception of portions of a signal from one channel into another. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 927. |
The spectral component of noise associated with kth frequency is given, in the limit as Δf → 0 by nk(t) written as nk(t) = Ck cos (2pk Δft + θk) Consider the following statements as regards Ck and θk Ck and θk are independent of one anotherCk and θk are independent of the amplitude of a spectral component at a different frequencyCt and θk are independent of the phase of a spectral component at a different frequency Which of the above statements are correct? |
| A. | 1, 2 only |
| B. | 1, 3 only |
| C. | 1, 2, 3 |
| D. | 2, 3 only |
| Answer» D. 2, 3 only | |
| 928. |
In a square law modulator, the carrier frequency should be __________ times than the highest modulating frequency. |
| A. | 1 |
| B. | 2 |
| C. | 4 |
| D. | 3 |
| Answer» E. | |
| 929. |
In a colour TV receiver, which of the following incorporates colour saturation control? |
| A. | Chroma detector |
| B. | Colour killer circuit |
| C. | SAW filter |
| D. | Chroma amplifier |
| Answer» E. | |
| 930. |
In a radar system the solution to blind speed problem is to |
| A. | use MTI |
| B. | use monopoles |
| C. | vary PRF |
| D. | change Doppler frequency |
| Answer» D. change Doppler frequency | |
| 931. |
Sound waves are electromagnetic waves. |
| A. | 1 |
| B. | |
| Answer» C. | |
| 932. |
In PM, without any modulation, all the transmitted pulses have the same |
| A. | amplitude |
| B. | width |
| C. | amplitude and spacing |
| D. | amplitude, spacing and width |
| Answer» E. | |
| 933. |
Which of the following antennas is not wide band? |
| A. | Marconi |
| B. | Helical |
| C. | Folded dipole |
| D. | Discone |
| Answer» B. Helical | |
| 934. |
In a TV receiver the raster is normal but there is no sound and quality of picture is poor. The defective part is |
| A. | power supply |
| B. | loudspeaker |
| C. | AGC, video IF amplifier, RF amplifier |
| D. | horizontal oscillator |
| Answer» D. horizontal oscillator | |
| 935. |
A pre-emphasis circuit |
| A. | boosts base frequencies |
| B. | pre amplifies the complete audio band |
| C. | amplifies higher audio frequencies |
| D. | converts FM into phase modulation |
| Answer» D. converts FM into phase modulation | |
| 936. |
Which of the following is most likely to be found in an SSB transmitter? |
| A. | Class A, RF output amplifier |
| B. | Class B, RF amplifier |
| C. | Tuned modulator |
| D. | Class C, audio amplifier |
| Answer» C. Tuned modulator | |
| 937. |
In a television transmitter, the output stage is most likely to be |
| A. | screen modulated class C amplifier |
| B. | plate modulated class C amplifier |
| C. | grid modulated class A amplifier |
| D. | grid modulated class C amplifier |
| Answer» E. | |
| 938. |
A 1000 kHz carrier wave modulated 40% at 40000 Hz is applied to a resonant circuit tuned to a carrier frequency and having Q = 140. What is the degree of modulator after transmission through the circuit? |
| A. | 0.4 |
| B. | 0.2 |
| C. | 0.27 |
| D. | 0.54 |
| Answer» D. 0.54 | |
| 939. |
In a CD player the laser uses |
| A. | silicon semiconductor |
| B. | silicon/germanium semiconductor |
| C. | aluminium gallium arsenide semiconductor |
| D. | none of the above |
| Answer» D. none of the above | |
| 940. |
Consider the following: A TV receiver antenna should pick up the TV signal and develop maximum voltage from the available strength of signalIt should reject unwanted signalsIt should not suffer from co-channel interferenceIt should have a very narrowband The correct statements are |
| A. | 1 and 2 only |
| B. | 1, 2 and 3 only |
| C. | 1, 2, 3, 4 |
| D. | 2, 3 only |
| Answer» C. 1, 2, 3, 4 | |
| 941. |
MEWS stands for |
| A. | Missile Early Warning System |
| B. | Moving Target Early warning System |
| C. | Missile Early Warning Signal |
| D. | Moving Target Early Warning Signal |
| Answer» B. Moving Target Early warning System | |
| 942. |
If k is Boltzmann's constant, T0 is standard ambient temperature, δf is bandwidth of receiver, F is noise figure, the minimum receivable signal in a radar receiver is given by |
| A. | k T0(δf)(F) |
| B. | k T0(δf)(F - 1) |
| C. | |
| Answer» C. | |
| 943. |
Assertion (A): A composite video signal has synchronising pulses.Reason (R): It is necessary to synchronise the scanning process in the transmitter and receiver. |
| 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 | |
| 944. |
The total bandwidth needed for an AM signal at 55.25 MHz with 0.5 MHz video modulation is |
| A. | 0.25 MHz |
| B. | 0.5 MHz |
| C. | 1 MHz |
| D. | 10 MHz |
| Answer» D. 10 MHz | |
| 945. |
Digital television is also called |
| A. | High digital television |
| B. | High definition television |
| C. | High deflection television |
| D. | High display television |
| Answer» C. High deflection television | |
| 946. |
Which of the following can provide two or more voice circuits with the same carrier? |
| A. | SSB |
| B. | Carrier reinsertion |
| C. | Lincompex |
| D. | Independent side band system |
| Answer» C. Lincompex | |
| 947. |
Which of the following pulse communication system is inherently immune to noise? |
| A. | PPM |
| B. | PCM |
| C. | PWM |
| D. | PAM |
| Answer» C. PWM | |
| 948. |
Automatic sensitivity control by target voltage control is easily possible in |
| A. | Vidicon |
| B. | Plumbicon |
| C. | New vicon |
| D. | both (b) and (c) |
| Answer» B. Plumbicon | |
| 949. |
AC hum is picked up from power cables |
| A. | 1 |
| B. | |
| Answer» C. | |
| 950. |
The decorative lighting works on the principle of |
| A. | periodic switching on and off |
| B. | special inverter |
| C. | rectifier |
| D. | motor |
| Answer» B. special inverter | |