MCQOPTIONS
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MCQOPTIONS
This section includes 147 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.
| 101. |
A trimmer is basically a |
| A. | insulator |
| B. | inductor |
| C. | capacitor |
| D. | variable resistor |
| Answer» D. variable resistor | |
| 102. |
In a radio receiver |
| A. | all stages contribute equally to noise |
| B. | RF stage has no effect on S/N ratio |
| C. | mixer stage contributes most of the noise generated |
| Answer» D. | |
| 103. |
A receiver having an RF amplifier and an IF of 450 kHz, has Q of the coils 65 and an incoming frequency of 1200 kHz. The image rejection of the receiver is |
| A. | 5870 |
| B. | 3655 |
| C. | 236 |
| D. | 13.3 |
| Answer» D. 13.3 | |
| 104. |
Neutralization is used in RF amplifiers to |
| A. | stop oscillation |
| B. | increase bandwidth |
| C. | improve selectivity |
| D. | all of the above |
| Answer» B. increase bandwidth | |
| 105. |
In a broadcast superheterodynes receiver having no RF amplifier, the loaded Q of the antenna coupling circuit is 100. If the intermediate frequency is 455 kHz. The image frequency at 25 MHz will be |
| A. | 24.09 MHz |
| B. | 24.54 MHz |
| C. | 25.45 MHz |
| D. | 25.91 MHz |
| Answer» E. | |
| 106. |
Standard AM radio broadcasts are confined to |
| A. | MF |
| B. | HF |
| C. | VHF |
| D. | UHF |
| Answer» B. HF | |
| 107. |
The selectivity curve of a standard receiver is represented by |
| A. | curve A |
| B. | curve B |
| C. | curve C |
| D. | curve D |
| Answer» D. curve D | |
| 108. |
The noise produced by a resistor is proportional to |
| A. | absolute temperature |
| B. | (absolute temperature)2 |
| Answer» B. (absolute temperature)2 | |
| 109. |
Which of the following statement about the amplitude limiter is not valid? |
| A. | Leak type bias must be used |
| B. | Output must be tuned |
| C. | The circuit is always biased in class C, by virtue of the leak type bias |
| D. | When the input increases past the threshold of limiting, the gain decreases to keep the output constant |
| Answer» D. When the input increases past the threshold of limiting, the gain decreases to keep the output constant | |
| 110. |
Modulated carrier power in FM |
| A. | increases with modulating signal power |
| B. | decreases with modulating signal power |
| C. | is independent of the modulating signal power |
| D. | none |
| Answer» D. none | |
| 111. |
A duplexer is a device used to |
| A. | feed more than one receiver from a single antenna |
| B. | connect two transmitters to the same antenna |
| C. | connect a receiver and a transmitter to the same antenna |
| D. | none of these |
| Answer» D. none of these | |
| 112. |
Which of the following is same in AM and FM receivers? |
| A. | Demodulator |
| B. | AGC |
| C. | IF amplifier |
| D. | All of the above |
| Answer» D. All of the above | |
| 113. |
Padders are used in a receiver to |
| A. | discard the carrier |
| B. | facilitate tracking |
| C. | filter the input signal |
| D. | suppress noise |
| Answer» C. filter the input signal | |
| 114. |
If the intermediate frequency of a superheterodyne receiver falls within the tuning range of the receiver |
| A. | Unsuitability will occur |
| B. | Heterodyne whistles will be heard |
| C. | Tuning to the frequency band immediately adjacent to the intermediate frequency will become impossible |
| D. | All of the above |
| Answer» E. | |
| 115. |
The sensitivity of a superheterodyne receiver is determined by |
| A. | the gain IF amplifier |
| B. | the gain of RF amplifier |
| C. | the noise figure |
| D. | all of the above |
| Answer» E. | |
| 116. |
Which one of the following is not a useful quantity for comparing the noise performance of receivers? |
| A. | Noise figure |
| B. | Noise temperature |
| C. | Input noise voltage |
| D. | Equivalent noise resistance |
| Answer» D. Equivalent noise resistance | |
| 117. |
In a ratio detector |
| A. | the linearity is worse than in a phase discriminator |
| B. | the output is twice that obtainable from a similar phase discriminator |
| C. | stabilization against signal strength variations is provided |
| D. | the circuit is the same as in a discriminator, except that the diodes are reversed |
| Answer» B. the output is twice that obtainable from a similar phase discriminator | |
| 118. |
As compared to tuned radio frequency receivers which of the following is the advantage of using superheterodyne receivers? |
| A. | High gain and better sensitivity |
| B. | Better selectivity at high frequencies |
| C. | Stability |
| D. | Noise suppression |
| Answer» B. Better selectivity at high frequencies | |
| 119. |
In a transistor receiver, the use of FET as the first stage amplifier is likely to |
| A. | improve selectivity of the receiver |
| B. | improve the effectiveness of the AGC |
| C. | reduce the effect of negative peak clipping |
| D. | reduce the effect of noise at all frequencies |
| Answer» D. reduce the effect of noise at all frequencies | |
| 120. |
In a radio receiver, the local oscillator is tuned to a frequency |
| A. | lower than the incoming frequency |
| B. | higher than the incoming frequency |
| C. | equal to incoming frequency |
| D. | any of the above |
| Answer» C. equal to incoming frequency | |
| 121. |
A low ratio of the A.C. load impedance of a diode detector results in |
| A. | diagonal clipping |
| B. | poor AGC operation |
| C. | poor AF response |
| D. | negative peak clipping |
| Answer» E. | |
| 122. |
Noise generated in a resistor is also known as |
| A. | partition noise |
| B. | white noise |
| C. | thermal noise |
| D. | shot noise |
| Answer» D. shot noise | |
| 123. |
The sensitivity curve of a standard receiver is represented by |
| A. | curve A |
| B. | curve B |
| C. | curve C |
| D. | curve D |
| Answer» D. curve D | |
| 124. |
In a radio receiver, if the intermediate frequency is too high |
| A. | Selectivity will be poor |
| B. | Tracking difficulties will be least |
| C. | Adjacent channel rejection will improve |
| D. | All of the above will occur |
| Answer» B. Tracking difficulties will be least | |
| 125. |
In a superheterodyne receiver with an IF of 450 kHz is tuned to a signal at 1200 kHz. The image frequency is |
| A. | 750 kHz |
| B. | 990 kHz |
| C. | 1650 kHz |
| D. | 2100 kHz |
| Answer» E. | |
| 126. |
Which of the following statement about receivers is false? |
| A. | Double conversion is used to improve image rejection |
| B. | Double conversion is used to improve selectivity |
| C. | Variable sensitivity is used to improve selectivity |
| D. | Variable sensitivity is used to eliminate selective fading |
| Answer» E. | |
| 127. |
It is known that noise phase modulates the FM wave. As the noise side band frequency approaches the carrier frequency, the noise amplitude |
| A. | will increase |
| B. | will decrease |
| C. | will remain constant |
| D. | will reduce to negligible value |
| Answer» C. will remain constant | |
| 128. |
EM 84 tube is used in radio receivers as |
| A. | audio amplifier |
| B. | RF amplifier |
| C. | full wave rectifier |
| D. | magic eye |
| Answer» E. | |
| 129. |
Which of the following cannot be used to demodulate SSB? |
| A. | Complete phase-shift generator |
| B. | Product detector |
| C. | Diode balanced modulator |
| D. | Bipolar transistor balanced modulator |
| Answer» E. | |
| 130. |
When fs is the signal frequency and fi is the intermediate frequency, then image frequency fsi is given by |
| A. | fsi = fs - 2fi |
| B. | fsi = fs + 2fi |
| Answer» C. | |
| 131. |
FM amplifier in a superheterodyne receiver |
| A. | increases selectivity |
| B. | suppresses noise |
| C. | provides improved tracking |
| D. | improves the rejection of the image frequency |
| Answer» E. | |
| 132. |
In a receiver, which of the following device has RF input but IF output? |
| A. | Loudspeaker |
| B. | Frequency changer |
| C. | Demodulator |
| D. | Audio amplifier |
| Answer» C. Demodulator | |
| 133. |
FM receivers using the standard 88 to 108 MHz band use IF of |
| A. | 8 MHz |
| B. | 9.9 MHz |
| C. | 10.7 MHz |
| D. | 12.2 MHz |
| Answer» D. 12.2 MHz | |
| 134. |
The selectivity of most receivers is determined largely by |
| A. | sensitivity |
| B. | characteristics of IF section |
| C. | antenna direction |
| D. | all of the above |
| Answer» C. antenna direction | |
| 135. |
In a broadcast superheterodyne receiver |
| A. | the local oscillator operates below the signal frequency |
| B. | local oscillator frequency is normally double the IF |
| C. | RF amplifier normally works at kHz above the carrier frequency |
| D. | mixer input must be tuned to the signal frequency |
| Answer» E. | |
| 136. |
In a superheterodyne receiver, the IF is 455 kHz. If it is tuned to 1200 kHz, the image frequency will be |
| A. | 1655 kHz |
| B. | 2110 kHz |
| C. | 745 kHz |
| D. | 910 kHz |
| Answer» C. 745 kHz | |
| 137. |
A transmitter serial current contains |
| A. | carrier frequencies |
| B. | audio frequencies |
| C. | radio frequencies |
| D. | none of the above |
| Answer» D. none of the above | |
| 138. |
The selectivity of a radio receiver is |
| A. | its ability to reject adjacent unwanted signals |
| B. | its ability to amplify weak signals |
| C. | the frequency at which it gives maximum amplification to signal. |
| D. | its ability to suppress noise. |
| Answer» B. its ability to amplify weak signals | |
| 139. |
In a superheterodyne receiver |
| A. | the IF stage has better selectivity than RF stage |
| B. | the RF stage has better selectivity than IF stage |
| C. | the RF stage has same selectivity than IF stage |
| D. | none of the above |
| Answer» B. the RF stage has better selectivity than IF stage | |
| 140. |
In a receiver, which of the following device has IF input but RF output? |
| A. | Demodulator |
| B. | Loudspeaker |
| C. | Audio amplifier |
| D. | Frequency changer |
| Answer» B. Loudspeaker | |
| 141. |
An unmodulated voltage 10 V effective is applied to a dioxide detector in which load resistance is 4 x 10-5 ohms. A micrometer shows that the rectified DC current in this resistance is 30 A. The input resistance of the detector is |
| A. | 114 kW |
| B. | 336 kW |
| C. | 384 kW |
| D. | 455 kW |
| Answer» C. 384 kW | |
| 142. |
In superheterodyne receivers, the local oscillator is used to |
| A. | detect the modulating signal |
| B. | amplify the received modulated carrier |
| C. | shift the frequency of the received modulated carrier to the IF band |
| D. | Demodulator |
| Answer» D. Demodulator | |
| 143. |
Which of the following should be used in order to prevent overloading or the last IF amplifier in a receiver? |
| A. | Variable selectivity |
| B. | Variable sensitivity |
| C. | Double conversion |
| D. | Squelch |
| Answer» C. Double conversion | |
| 144. |
Which are the popular IF frequencies for microwave and radar receivers operating on frequencies in the range 1 to 10 GHz |
| A. | 30, 60 and 70 kHz |
| B. | 3, 6 and 7 kHz |
| C. | 30, 60 and 70 MHz |
| D. | 3, 6 and 7 GHz |
| Answer» D. 3, 6 and 7 GHz | |
| 145. |
Noise limiter is provided on AM receivers to |
| A. | reduce interfering noise due to ignition system |
| B. | reduce noise due to electrical storms |
| C. | reduce interference due to electrical machinery |
| D. | all of the above |
| Answer» E. | |
| 146. |
In a radio receiver, if the intermediate frequency is too low |
| A. | Image-frequency rejection will improve |
| B. | Selectivity will be too sharp |
| C. | The frequency selectivity of the local oscillator will have to be lowered |
| D. | All of the above |
| Answer» C. The frequency selectivity of the local oscillator will have to be lowered | |
| 147. |
The noise generated by a resistor depends upon |
| A. | its resistance value |
| B. | its operating temperature |
| C. | both its resistance value and operating temperature |
| D. | none of the above |
| Answer» C. both its resistance value and operating temperature | |