Communications MCQ Set 1
1. Why a helical antenna is used for satellite tracking?
a) because of its circular polarization
b) because of its broad bandwidth
c) because of its low bandwidth
d) because of its good front to back ratio
2. Which one of the following noise becomes of great importance at high frequencies?
a) random noise
b) shot noise
c) impulse noise
d) transit-time noise
3. TDM stands for ________
a) Time Division Multiplexing
b) Time Difference Multiplexing
c) Time Division Method
d) Time Data Method
4. Which one of the following statement is false?
a) HF mixers are generally noisier
b) Voltage of impulse noise is independent of bandwidth
c) Thermal noise is not dependent on frequency
d) Industrial noise is impulse type noise
5. Which of broad classifications of noise are most difficult to treat?
a) noise generated in the receiver
b) noise generated in the transmitter
c) externally generated noise
d) internally generated noise
6. FDM is an analog multiplexing technique used to combines ________
a) analog signals
b) digital signals
c) both analog and digital signals
d) alternatively passes analog and digital signals
7. What points must be important to remember, when we deal with random noise calculations?
a) all calculations are based on peak to peak values
b) calculations are based on peak values
c) calculations are based on average values
d) calculations are based on RMS values
8. Which of the following statement is true?
a) Random noise power is inversely proportional to bandwidth
b) Flicker noise is demodulation to noise
c) Noise mixers is caused by inadequate image frequency rejection
d) A random voltage across a resistance cannot be calculated
9. Which of the following statement is false?
a) Modulation is used to reduce the bandwidth
b) Modulation is used to separate different transmissions
c) Modulation is used to allow the use of practical antennas
d) Modulation is used to ensure that wave is transmitted over long distances
10. Which of the steps is not included in the process of reception?
Communications MCQ Set 2
1. The image frequency of a superheterodyne receiver ___________
a) is created within the receiver itself
b) is due to insufficient adjacent channel rejection
c) is not rejected to be the IF tuned circuits
d) is independent of the frequency to which the receiver is tuned
2. Which one of the following circuits could not demodulate SSB?
a) Balance Modulator
b) Product Modulator
d) Phase discriminator
3. Which of the following statement is true about a radio detector?
a) the linearity is worse than in phase discriminator
b) there is stabilization against signal strength variations
c) the final output is twice of that obtainable from a similar phase discriminator
d) the circuit is same as in a discriminator, except that the diodes are reversed.
4. Envelope of AM wave has the same shape as the message of baseband signal.
5. To prevent overloading of the IF amplifier in a receiver, one should use _________
a) variable sensitivity
b) variable selectivity
c) double conversion
6. In a broadcast superheterodyne receiver, the ____________
a) Local oscillator always operates below the frequency of transmitted signal
b) Input of mixer must be tuned to the signal frequency
c) Local oscillator frequency should be double than that of IF
d) RF amplifier normally works at 455 KHz above the carrier frequency
7. Which of the following statement is false regarding Armstrong modulation system?
a) The system is basically phase, not frequency modulated
b) AFC is not needed as crystal oscillator is used
c) Frequency multiplication must be used
d) Equalization is necessary
8. If the target cross section is changing, the best system for accurate tracking is __________
a) sequential switching
b) lobe switching
c) conical scanning
9. What do you understand by low level AM?
a) Output power is low
b) Modulation is done at high power of carrier and modulating signal
c) Collector Modulation Method is low level AM
d) Output power is high
10. After a target has been acquired, the best scanning system for tracking is _________
Communications MCQ Set 3
1. The discone antenna is ________
a) useful direction-finding antenna
b) used as a radar receiving antenna
c) circularly polarized
d) useful as UHF receiving antenna
2. Which one of the following is not an omnidirectional antenna?
d) Half-wave dipole
3. If the value of a resistor creating thermal noise is doubled. The noise power generator is therefore ________
4. Which one of the following is not a useful quantity for comparing the noise performance of receivers?
a) Input noise voltage
b) Equivalent noise resistance
c) Noise Figure
d) Figure of merit
5. What is Synchronous TDM?
a) gives same amount of time to each device
b) gives same amount of frequency to each device
c) gives variable time to each device
d) gives variable frequency to each device
6. Which of the following is the most generally used term for comparing amplifier noise characteristics?
a) signal to noise ratio
b) shot noise
c) noise factor
d) figure of merit
7. The number of lines per field in the United States TV system is _________
8. The number of frames per second in the United States TV system is _________
9. Why interlacing is used in television?
a) to produce the illusion of motion
b) to ensure that all the lines on screen are scanned
c) to reduce the disturbances
d) to avoid flicker
10. The signals sent by the TV transmitters to ensure correct scanning in the receiver are called luminance.
11. As distance increases ________
a) Packet size also increases
b) Packet size decreases
c) Packet size becomes twice of its previous value
d) Packet size becomes half
12. If 32 equally probable events exists and we have to select one of them, number of required bits is?
Communications MCQ Set 4
1. What is the probability density function of thermal noise?
2. Neutralization cancels unwanted feedback by bypassing the feedback to the neutral or ground plane.
3. What is the spectral density of white noise?
a) varies with bandwidth
b) varies with frequency
4. Which is the true statement about noise performance of wideband FM system?
a) it is independent of modulation index
b) it is generally poorer than that of an AM system
c) it is independent of signal to noise ratio
d) it exhibits a threshold
5. What is the power ratio of one decibel?
6. Bit is a unit of ________
a) Channel Capacity
d) Rate of information
7. What is the maximum possible value of entropy?
8. If we double the value of resistor then how it affects the thermal noise power?
a) gets doubled
b) gets halved
c) gets quadrupled
d) remains unchanged
9. What is the auto correction function of white noise?
a) Impulse Function
b) Step Function
d) Linear Function
10. Pick odd one about:
a) Cosmic noise
b) Galactic noise
c) Atmospheric noise
d) Polar noise
Communications MCQ Set 5
1. In AM receiver, the oscillator frequency is always ________
a) lower than signal frequency
b) higher than signal frequency
c) equal to signal frequency
d) equal to 1000KHz
2. What you understand by the term discone antenna?
a) combination of disc and cone
b) combination of disc and cone with a spacing of ʎ⁄4
c) combination of disc and cone with a spacing of ʎ⁄2
d) same as a simple antenna
3. Which of the following receiver does not have amplitude limiter stage?
d) Both AM and FM
4. Most of the amplification of received signal is obtained in a superheterodyne receiver from ________ stage.
c) Power Amplifier
d) can be from IF or RF
5. Padder capacitor can be used to achieve three point tracking.
6. Any signal and its Hilbert transform are mutually orthogonal.
7. If the output power of radio receiver is doubled then the volume is increased by _________
a) 3 dB
b) 2 dB
c) -3 dB
d) -2 dB
8. If selectivity is poor then the receiver has poor _________
b) diverse reception
d) transmission and reception
9. In FM the carrier deviation is determined by ________
10. In systems, pre-emphasis is used to amplify ________
a) high frequency
b) low frequency
c) both high and low frequency