Q.1. 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

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).

Q.2. The selectivity of most receivers is determined largely by …………

A. sensitivity
B. characteristics of IF section
C. antenna direction
D. all of the above

Q.3. 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

Q.4. 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 rejection ratio at 25 MHz will be ………

A. 1.116
B. 1.386
C. 2.116
D. 2.386

A. High gain and better sensitivity
B. Better selectivity at high frequencies
C. Stability
D. Noise suppression

Q.6. 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

Q.7. FM amplifier in a superheterodyne receiver

A. increases selectivity
B. suppresses noise
C. provides improved tracking
D. improves the rejection of the image frequency

B. facilitate tracking
C. filter the input signal
D. suppress noise

Q.9. 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

Q.10. Which of the following oscillator is generally not used at VHF?

A. Colpitts oscillator
B. Clapp oscillator
C. Armstrong oscillator
D. Ultra Audio oscillator

Q.11. 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

Q.12. The output of a diode detector contains

A. D.C. voltage
B. modulating signal
C. RF ripple
D. all of the above

Q.13. Which of the following noise does not occur in transistors?

A. Partition noise
B. Shot noise
C. Flicker noise
D. Resistance noise

Q.14. Noise generated in a resistor is also known as

A. partition noise
B. white noise
C. thermal noise
D. shot noise

Q.15. Which of the following is used to provide tracking between RF amplifier and local oscillator stages of receiver?

A. Variable tuning inductor
B. Ganged tuning inductor
C. Variable capacitor
D. Variable preset

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.

Q.17. 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

A. audio amplifier
B. RF amplifier
C. full wave rectifier
D. magic eye

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

Q.20. 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

Q.21. 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. none of the above

Q.22. Which of the following is same in AM and FM receivers?

A. Demodulator
B. AGC
C. IF amplifier
D. All of the above

Q.23. A notch filter is sometimes used in communication receivers to

A. reduce receiver gain at some specific frequency
B. increase receiver gain at some specific frequency

Q.24. 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

Q.25. 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

Q.26. 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

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

Q.28. The function of an AM detector circuit is to

A. rectify the input signal
C. provide audio signal
D. all of the above

Q.29. 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

Q.30. Most popular IF for receivers tuning to 540 to 1650 kHz is

A. 433 kHz
B. 455 kHz
C. 545 kHz
D. 555 kHz

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

Q.32. 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

Q.33. A heterodyne frequency changer is called a

A. Modulator
B. Mixer
C. Demodulator
D. Frequency translator

A. improved image frequency rejection
B. improved rejection of adjacent unwanted signals
C. prevention of re-radiation of the local oscillator through the antenna of the receiver
D. all of the above

Q.35. 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

Q.36. 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

Q.37. Neutralization is used in RF amplifiers to

A. stop oscillation
B. increase bandwidth
C. improve selectivity
D. all of the above

Q.38. 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

Q.39. In a receiver, which of the following device has IF input but RF output?

A. Demodulator
B. Loudspeaker
C. Audio amplifier
D. Frequency changer

Q.40. Transistor are free from which type of noise?

A. Resistance noise
B. Partition noise
C. Flicker noise
D. Shot noise

A. MF
B. HF
C. VHF
D. UHF

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

Q.43. 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

Q.44. A transmitter serial current contains

A. carrier frequencies
B. audio frequencies
D. none of the above

Q.45. 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

Q.46. In a communication system, noise is most likely to affect the signal

A. at the transmitter
B. in the channel
C. in the information source
D. at the destination

Q.47. 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

Q.48. 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

Q.49. 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

Q.50. A trimmer is basically a

A. insulator
B. inductor
C. capacitor
D. variable resistor

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
D. none of the above

Q.52. 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

A. the local oscillator frequency is made higher than the incoming signal frequency
B. the local oscillator frequency is made lower than the incoming signal frequency
C. the local oscillator frequency is made equal to the incoming signal frequency
D. none of the above

A. mixer stage
B. power supply
C. power amplifier
D. equally from above three

Q.55. Power spectral density of white noise

A. is constant with frequency
B. increases with frequency
C. decreases with frequency
D. none

Q.56. In a FM waveform, the side bands are spaced at intervals equal to

A. four times the modulating frequency
B. twice the modulating frequency
C. half the modulating frequency
D. modulating frequency

Q.57. 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

Q.58. A padder is basically a/an

A. insulator
B. variable resistor
C. capacitor
D. inductor

Q.59. In a radio receiver, the local oscillator is always tuned to a frequency higher than the incoming frequency to

A. facilitate tracking
B. allow permit adequate frequency coverage without switching
C. facilitate image frequency rejection
D. all of the above

Q.60. When a superheterodyne receiver is tuned to 455 kHz, its local oscillator provides a mixer with the input at 1010 kHz. The image frequency is

A. 555 kHz
B. 1010 kHz
C. 1465 kHz
D. 1920 kHz

Q.61. 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 1000 kHz will be

A. 1010 kHz
B. 1455 kHz
C. 1910 kHz
D. 545 kHz

Q.62. In a superheterodyne receiver, the IF stage has better selectivity than RF stage because

A. of higher frequency
B. of lower frequency
C. of high L/C ratio
D. of constant passband

Q.63. An arbitrary signal m (t) has zero average value and it is bandlimited to 3.2 kHz. It is sampled at the rate of 8 K samples/S. The samples are passed through an ideal bandpass filter with centre frequency of 32 kHz and bandwidth of 6.4 kHz. The output of band pass filter is

A. AM-DSB signal with suppressed carrier
B. AM-DSB signal with carrier
C. AM-SSB signal with carrier
D. a sequence of exponentially decaying sine waves

Q.64. The purpose of incorporating a pre-selector stage in a receiver is to

A. provide higher selectivity
B. provide higher fidelity
C. improve linearity
D. larger passband

Q.65. Vividh Bharati programme is transmitted in

A. short wave
B. medium frequency
C. very high frequency
D. all of the above

Q.66. The image frequency of a superheterodyne receiver is

A. independent of the frequency at which the receiver is tuned
B. always outside the operating range of the receiver
C. typical to FM receivers only
D. not rejected by the IF tuned circuits

Q.67. In a receiver, which of the following device has RF input but IF output?

A. Loudspeaker
B. Frequency changer
C. Demodulator
D. Audio amplifier

Q.68. The IF stage of a receiver employs

A. capacitive coupling
B. impedance coupling
C. double-tuned transformer coupling
D. single-tuned transformer coupling

Q.69. A FM signal with modulation index Mf is passed through a frequency doubler. The wave in the output of the doubler will have modulation index of

A. Mf
B. Mf/2
C. 2Mf
D. UMf

Q.70. Double spotting in a receiver is due to

A. poor sensitivity of RF amplifier
B. high gain of IF amplifier
D. all of the above

Q.71. Three point tracking can be achieved with

A. gang condenser
B. variable selectivity
D. any of the above

Q.72. 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

A. synchronous
B. envelope detector
D. none of the above

Q.74. The source of which of the following noise is different from that of the remaining ?

A. Solar noise
B. Cosmic noise
C. Galactic noise
D. Atmospheric noise

Q.75. A receiver having poor IF selectivity will also have poor

A. sensitivity
B. double spotting
C. blocking
D. all of the above

Q.76. Statement 1
Diode is the most common device used for demodulation.
Statement 2
A discriminator is a FM detector

A. Statement 1 is true but statement 2 is false
B. Statement 1 is false but statement 2 is true
C. Both the statements are true
D. Both the statements are false

Q.77. Which of the following statement about the advantage of phase discriminator over the slope detector is false?

A. Fewer tuned circuits
B. Better linearity
C. Greater limiting
D. Much easier alignment

Q.78. Fidelity of a receiver represents

A. the sensitivity expressed in terms of voltage that must be applied to the receiver input to give a standard output
B. the extent to which the receiver is capable of distinguishing between the desired signal and other frequencies
C. the variation of the output with the modulation frequency when the output impedance is a resistance
D. none of the above

Q.79. Which of the following produces upper and lower side frequencies?

A. Microphone
B. Demodulator in a superheterodyne receiver
C. Modulator in a. radio transmitter

Q.80. The passband of the tuned circuits of a radio receiver should be equal to

A. 20 kHz
B. 455 kHz
C. 1455 kHz
D. more than 455 kHz

Q.81. 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. In receivers operating upto the limit of shortwave broadcasting the local oscillator often used is

A. Armstrong oscillator
B. Colpitts oscillator
C. Clapp oscillator
D. Ultra Audio oscillator

A. better sensitivity
B. improved signal-to-noise ratio
C. better coupling of receiver to the antenna
D. all of the above

Q.83. In an FM signal, the power

A. increases as the modulation index increases
B. reduces as the modulation index increase
C. increases as the modulation index decreases
D. remains constant when the modulation index increases

Q.84. 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 efficiency of detection is

A. 34%
B. 55.5%
C. 68.8%
D. 84.7%

Q.85. Selectivity varies with receiving frequency, frequency is raised.

A. Somewhat better when the receiving frequency is raised
B. Somewhat better at intermediate frequency
C. Somewhat worse when the receiving frequency is lowered
D. Somewhat worse when the receiving frequency is raised

Q.86. 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

Q.87. Most of the amplification of the received signal is obtained in a superheterodyne receiver from the

A. IF stage
B. RF stage
C. power amplification stage
D. none of the above

A. instability
C. bandwidth variation
D. all of the above

Q.89. Which of the following noise becomes of great importance at high frequencies?

A. Transit-time noise
B. Shot noise
C. Flicker noise
D. Agitation noise

Q.90. Superheterodyne receiver can be used in

A. AM
B. FM
C. SSB
D. All of the above

Q.91. In a receiver, at higher frequencies

A. tracking will be improved
B. tracking will be poor
C. selectivity will be poor
D. image frequency rejection will be poor

Q.92. Which of the following circuit cannot be used to demodulate SSB?

A. Phase discriminator
B. Produce detector
C. Balanced modulator
D. Beat frequency oscillator

Q.93. High IF in a superheat receiver

A. improves selectivity
B. increases tracking problems
C. decreases tracking problems

Q.94. The typical squelch circuit

A. cuts off an IF amplifier when the AGC is maximum
B. cuts off an IF amplifier when the AGC is minimum
C. cuts off an audio amplifier when the carrier is absent
D. eliminates the RF interference when the signal is weak