Radio Receivers problems
- 1. In a radio receiver with simple AGC
Options- A. the highest AGC voltage is produced between stations
- B. the faster the AGC time constant, the more accurate the output
- C. an increase in signal strength produces more AGC
- D. the audio stage gain is normally controlled by AGC Discuss
Correct Answer: an increase in signal strength produces more AGC
- 2. In a superheterodyne receiver, the IF is 455 kHz. If it is tuned to 1200 kHz, the image frequency will be
Options- A. 1655 kHz
- B. 2110 kHz
- C. 745 kHz
- D. 910 kHz Discuss
Correct Answer: 2110 kHz
Explanation:
A signal (image) can interfere with a superheterodyne receiver if fits the following equation.
Image = Signal +/- 2 x I.F.
Which says that a signal has the capacity to interfere with a superhet receiver if its frequency is equal to the signal frequency (1200 kHz in our question) plus or minus twice the IF (455 kHz in our question).
So one possible image is: 1200 + ( 2 x 455 ) = 2110 kHz (possible).
And the other: 1200 - ( 2 x 455 ) = 290 kHz (not likely).
- 3. 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
Options- A. 24.09 MHz
- B. 24.54 MHz
- C. 25.45 MHz
- D. 25.91 MHz Discuss
Correct Answer: 25.91 MHz
- 4. Noise generated in a resistor is also known as
Options- A. partition noise
- B. white noise
- C. thermal noise
- D. shot noise Discuss
Correct Answer: thermal noise
- 5. The function of an AM detector circuit is to
Options- A. rectify the input signal
- B. discard the carrier
- C. provide audio signal
- D. all of the above Discuss
Correct Answer: all of the above
- 6. Which of the following is same in AM and FM receivers?
Options- A. Demodulator
- B. AGC
- C. IF amplifier
- D. All of the above Discuss
Correct Answer: IF amplifier
- 7. In a radio receiver, if the intermediate frequency is too low
Options- 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 Discuss
Correct Answer: Selectivity will be too sharp
- 8. In a broadcast superheterodyne receiver
Options- 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 Discuss
Correct Answer: mixer input must be tuned to the signal frequency
- 9. If the intermediate frequency of a superheterodyne receiver falls within the tuning range of the receiver
Options- 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 Discuss
Correct Answer: All of the above
- 10. Which of the following oscillator is generally not used at VHF?
Options- A. Colpitts oscillator
- B. Clapp oscillator
- C. Armstrong oscillator
- D. Ultra Audio oscillator Discuss
Correct Answer: Armstrong oscillator
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