MCQOPTIONS
Saved Bookmarks
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.
| 1051. |
In pulse transmitter the ratio of time on to time off is called |
| A. | efficiency |
| B. | duty cycle |
| C. | base |
| D. | bandwidth |
| Answer» C. base | |
| 1052. |
In AM, if modulation index is more than 100%, then |
| A. | bandwidth increases |
| B. | the wave gets distorted |
| C. | power of the wave increases |
| D. | efficiency of transmission increases |
| Answer» C. power of the wave increases | |
| 1053. |
In a low level amplitude modulated system, the amplifier modulated stage must be |
| A. | class C |
| B. | linear |
| C. | non linear |
| D. | harmonic |
| Answer» C. non linear | |
| 1054. |
Which of the following is the indirect way of FM generation? |
| A. | Reactance bipolar transistor modulator |
| B. | Armstrong modulator |
| C. | Varactor diode modulator |
| D. | Reactance FM modulator |
| Answer» C. Varactor diode modulator | |
| 1055. |
The minimum step size required for a Delta modulator operating at 36 samples/sec to track the signal (here u(t) is the unit step function) x(t) = 125t (u(t) - u(t - 1)) + (250 - 125t) (u(t - 1) - u(t - 2)) So that slope overload is avoided, would be |
| A. | 43740 |
| B. | 43679 |
| C. | 43618 |
| D. | 43557 |
| Answer» C. 43618 | |
| 1056. |
Which SNR denotes excellent picture quality in TV? |
| A. | 50 dB |
| B. | 30 dB |
| C. | 15 dB |
| D. | 5 dB |
| Answer» B. 30 dB | |
| 1057. |
In FM 'guard band' is provided |
| A. | to limit upper frequency limit |
| B. | to limit lower frequency limit |
| C. | so that there is less adjacent channel interference |
| D. | to limit transmitted power of a station |
| Answer» D. to limit transmitted power of a station | |
| 1058. |
Assertion (A): The unit of telephone traffic measurement is erlang.Reason (R): International circuits for communication are fitted with echo suppressors. |
| 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 | |
| 1059. |
Which of the following antennas is circularly polarized? |
| A. | Yagi-Uda |
| B. | Parabolic reflector |
| C. | Small circular loop |
| D. | Helical |
| Answer» E. | |
| 1060. |
In a pulsed RADAR, the transmitter is connected to the antenna |
| A. | during pulse interval |
| B. | during interval between pulses |
| C. | all the time |
| D. | only during a fraction of pulse interval |
| Answer» B. during interval between pulses | |
| 1061. |
TV receivers use flyback switched mode power supply because |
| A. | it can supply many voltage outputs |
| B. | it does not require a filter choke and is cheap |
| C. | it has very good regulation at all loads |
| D. | both (a) and (c) |
| Answer» C. it has very good regulation at all loads | |
| 1062. |
In the television system in India, the aspect ratio is |
| A. | 0.16875 |
| B. | 0.12777777777778 |
| C. | 0.21111111111111 |
| D. | 0.17013888888889 |
| Answer» B. 0.12777777777778 | |
| 1063. |
The noise performance of a square law demodulator of AM signal is |
| A. | better than that of an envelope detector |
| B. | better than that of a synchronous detector |
| C. | identical with that of a synchronous detector |
| D. | poorer than that of an envelope detector |
| Answer» C. identical with that of a synchronous detector | |
| 1064. |
When the channel is noisy, producing a conditional probability of error p = 0.5; the channel capacity and entropy function would be, respectively, |
| A. | 1 and 1 |
| B. | 1 and 0.5 |
| C. | 0.5 and 1 |
| D. | 0 and 1 |
| Answer» E. | |
| 1065. |
Which of the following has the highest input impedance? |
| A. | CE |
| B. | CB |
| C. | CC |
| D. | Push pull |
| Answer» D. Push pull | |
| 1066. |
A plot of modulation index vs carrier amplitude yields a |
| A. | horizontal line |
| B. | vertical line |
| C. | parabola |
| D. | hyperbola |
| Answer» E. | |
| 1067. |
Quantizing error occurs in |
| A. | TDM |
| B. | FDM |
| C. | PCM |
| D. | PWD |
| Answer» D. PWD | |
| 1068. |
A MASER is a |
| A. | low noise device |
| B. | high noise device |
| C. | medium noise device |
| D. | may be either high or medium noise device |
| Answer» B. high noise device | |
| 1069. |
FM transmitting and receiving equipment as compared to AM equipment is |
| A. | costly |
| B. | cheaper |
| C. | almost equally costly |
| D. | none of the above |
| Answer» B. cheaper | |
| 1070. |
The seven segment display used in watches and clocks generally uses |
| A. | LED |
| B. | LCD |
| C. | Photodiode |
| D. | FET |
| Answer» B. LCD | |
| 1071. |
In FDM systems used for telephone, which modulation scheme is adopted? |
| A. | AM |
| B. | DSB-SC |
| C. | SSB-SC |
| D. | FM |
| Answer» E. | |
| 1072. |
The antenna current of an AM transmitter is 8 A. When only the carrier is sent, but it increases to 8.93 A. when the carrier is sinusoidally modulated. The percentage modulation is nearly |
| A. | 0.9 |
| B. | 0.8 |
| C. | 0.75 |
| D. | 0.7 |
| Answer» E. | |
| 1073. |
For a system to be designated as hi-fi, the signal to noise ratio should be at least |
| A. | 25 dB |
| B. | 50 dB |
| C. | 75 dB |
| D. | 100 dB |
| Answer» C. 75 dB | |
| 1074. |
In a TV receiver the video IF amplifier provides a gain of about |
| A. | 5 dB |
| B. | 20 dB |
| C. | 60 dB |
| D. | 200 dB |
| Answer» D. 200 dB | |
| 1075. |
Consider the following statements: In a radar system having a high value of the ratio (antenna diameter)/wavelength the maximum range is largegood target discrimination is achievedcapture area is increasedtarget acquisition is difficult 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 | |
| 1076. |
In figure the output v(t) is |
| A. | phase modulated signal |
| B. | amplitude modulated signal |
| C. | frequency modulated signal |
| D. | none of the above |
| Answer» D. none of the above | |
| 1077. |
Assertion (A): In FM all power amplifiers can be operated in class C Reason (R): FM is a constant amplitude modulation system. |
| 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 | |
| 1078. |
In a modulator it is found that the amplitude spectrum consists a component at fc, the carrier frequency and one component each at fc - fs and fc + fs where fs is the modulating signal frequency. Then the modulator used is |
| A. | AM |
| B. | AM or MBFM with modulation index 0.5 |
| C. | FM |
| D. | PAM |
| Answer» C. FM | |
| 1079. |
The main advantage of superheterodyne receiver is |
| A. | better tracking |
| B. | simple cut |
| C. | better alignment |
| D. | improvement in selectivity and sensitivity |
| Answer» E. | |
| 1080. |
A 1000 kHz carrier is simultaneously modulated by 300 Hz and 2 kHz audio sine wave. Which of the following frequencies will not be present in the output? |
| A. | 998 kHz |
| B. | 999.7 kHz |
| C. | 1000.3 kHz |
| D. | 700 kHz |
| Answer» E. | |
| 1081. |
Which of the following analog modulation scheme requires the minimum transmitted power and minimum channel bandwidth? |
| A. | VSB |
| B. | DSB-SC |
| C. | SSB |
| D. | AM |
| Answer» D. AM | |
| 1082. |
An FM radio receiver which is tuned to a 91.6 MHz broadcast station may receive an image frequency of __________ MHz. |
| A. | 102.3 |
| B. | 113 |
| C. | 70.2 |
| D. | 80.9 |
| Answer» C. 70.2 | |
| 1083. |
Indicate the false statement: If SWR on a transmission line is infinite, the line is terminated in |
| A. | open circuit |
| B. | short circuit |
| C. | pure reactance |
| D. | complex impedance |
| Answer» E. | |
| 1084. |
Which one of the following is correct? |
| A. | Coding reduces the noise in the signal |
| B. | Coding deliberately introduces redundancy into messages |
| C. | Coding increases the information rate |
| D. | Coding increases the channel bandwidth |
| Answer» B. Coding deliberately introduces redundancy into messages | |
| 1085. |
The characteristic impedance of a twin wire feeder used for TV signals is about |
| A. | 1000 ohm |
| B. | 500 ohm |
| C. | 300 ohm |
| D. | 100 ohm |
| Answer» D. 100 ohm | |
| 1086. |
When energy is fed into open wire transmission line the energy may get dissipated due to |
| A. | radiation |
| B. | conductor heating |
| C. | dielectric heating |
| D. | all of the above |
| Answer» E. | |
| 1087. |
Diffraction of EM waves |
| A. | arises only with spherical wave front |
| B. | may occur around the edge of an obstacle |
| C. | occurs when waves pass through a big slot |
| D. | none of the above |
| Answer» D. none of the above | |
| 1088. |
Assertion (A): In standing wave pattern, the nodes and anti nodes are separated by half wave-lengthReason (R): When line is terminated in resistance RL, the standing wave ratio is SWR = Z0/RL or RL/Z0 |
| 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 | |
| 1089. |
In VHS format width of audio track is |
| A. | 5 mm |
| B. | 2 mm |
| C. | 1 mm |
| D. | 0.1 mm |
| Answer» D. 0.1 mm | |
| 1090. |
In colour TV receiver, varactor diode is used for |
| A. | detection |
| B. | rectification |
| C. | tuning |
| D. | both (a) and (b) |
| Answer» D. both (a) and (b) | |
| 1091. |
In a 100% amplitude modulated signal, the power in the upper sideband when carrier power is to be 100 W and modulation system SSBSC, is |
| A. | 100 W |
| B. | 66 W |
| C. | 50 W |
| D. | 25 W |
| Answer» E. | |
| 1092. |
Some multiplexing arrangements for telephone system are Space multiplexingTime division multiplexingFrequency division multiplexing Which of the above allow transmission of many independent signals over a single channel? |
| A. | 1 only |
| B. | 2 and 3 only |
| C. | 1, 2, 3 |
| D. | 1 and 3 only |
| Answer» C. 1, 2, 3 | |
| 1093. |
At night the ionosphere can be considered to be consisting of |
| A. | D, E, F1 and F2 layers |
| B. | D, E, F1 layers |
| C. | D, E, F2 layers |
| D. | E and F2 layers |
| Answer» E. | |
| 1094. |
Household taperecorders generally use |
| A. | crystal microphone |
| B. | moving coil microphone |
| C. | condenser microphone |
| D. | cardioid microphone |
| Answer» B. moving coil microphone | |
| 1095. |
Circular polarization |
| A. | is useful in reducing depolarization effect on received wave |
| B. | involves critical alignment of transmitting and receiving antenna |
| C. | is useful in discrimination between reception of adjacent beams |
| D. | none of the above |
| Answer» B. involves critical alignment of transmitting and receiving antenna | |
| 1096. |
If the oscillator output is modulated by audio frequencies upto 10 kHz, the frequency range occupied by the side bands will be |
| A. | 711.9 kHz to 712.1 kHz |
| B. | 702 kHz to 722 kHz |
| C. | 692 kHz to 732 kHz |
| D. | 71.2 kHz to 71.20 kHz |
| Answer» C. 692 kHz to 732 kHz | |
| 1097. |
If ω is the frequency of modulating voltage in FM, the modulation index is proportional to |
| A. | ω |
| B. | 1/ω |
| C. | ω |
| D. | 1/ω |
| Answer» C. œâ | |
| 1098. |
Resonant circuits are used in |
| A. | audio amplifiers |
| B. | RF amplifiers |
| C. | both audio and RF amplifiers |
| D. | none of the above |
| Answer» C. both audio and RF amplifiers | |
| 1099. |
The standard intermediate frequency for FM ratio is |
| A. | 10.7 MHz |
| B. | 4.5 MHz |
| C. | 75 kHz |
| D. | 455 kHz |
| Answer» B. 4.5 MHz | |
| 1100. |
Consider a sampled signal y(t) = 5 x 10-6 x(t) where x(t) = 10 cos (8p x 103)t and ts = 100 μ sec. when y(t) is passed through an ideal low-pass filter with a cut off frequency of 5 kHz, the output of the filter is |
| A. | 5 x 10-6 cos (8p x 103)t |
| B. | 5 x 10-5 cos (8p x 103)t |
| C. | 5 x 10-1 cos(8p x 103)t |
| D. | 10 cos(8p x 103)t |
| Answer» C. 5 x 10-1 cos(8p x 103)t | |