Electronics And Communication MCQ Part-1
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Attempt Free Electronics And Communication MCQ Part-1 Here. Read The Important Electrical MCQ From Below.
(a) at the transmitter
(b)in the channel
(c)in the information source
(d)at the destination
Q2 INDICATE THE FALSE STATEMENT .MODULATION IS USED TO
(a)reduce the bw used
(b)separate different transmissions
(c)ensure that intelligence may be transmitted over long distances
(d)allow the use of practical antenna
Q3 ONE OF THE FOLLOWING NOISE BECOME OF GREAT IMPORTANCE AT HIGH FREQUENCY.IT IS THE
(a)shot noise
(b)random noise
(c)impulse noise
(d)transit time noise
Q4 INDICATE THE FALSE STATEMENT
(a)hf mixer are generally nosier than hf amplifiers
(b)impulse noise voltage is independent of bw
(c)thermal noise is independent of frequency at which it is measured
(d)industrial noise is usually of impulse type
Q5 THE VALUE OF THE RESISTOR CREATING THERMAL NOISE IS DOUBLED .THE NOISE POWER IS
(a)halved
(b)quadrupled
(c)doubled
(d)unchanged
Q6 ONE OF THE FOLLOWING IS NOT A USEFUL QUANTITY FOR COMPARING THE NOISE PERFORMANCE OF RECEIVERS
(A)i/p noise voltage
(b)equivalent noise resistance
(c)noise temp
(d)noise figure
Q7 INDICATE THE NOISE WHOSE SOURCE IS IN A CATEGORY DIFFERENT FROM THAT OF OTHER THREE
(A)solar noise
(B)cosmic noise
(C)atmospheric noise
(D)galgatic noise
Q8 IN A LOW LEVEL AM SYSTEM ,AMPLIFIERS FOLLOWING THE MODULATED SIGNAL MUST BE
(a)linear
(b)harmonic devices
(c)class c amplifiers
(d)non linear devices
Q9 LEAK TYPE BIAS IS USED IN A PLATE MODULATED CLASS C AMPLIFIER TO
(A)prevent tuned circuit damping
(b)prevent excessive grid current
(c)prevent over modulation
(d)increase the bw
Q10 THE O/P STAGE OF A TELEVISION TRANSMITTER IS MOST LIKELY TO BE A
(a)plate modulated class c amplifier
(b)grid modulated class c amplifier
(c)screen modulated class c amplifier
(d)grid modulated class a amplifier
(a)unchanged
(b)halved
(c)doubled
(d)increased by 50%
Q12 ONE OF THE ADVANTAGE OF BASE MODULATION OVER COLLECTOR MODULATION OF A TRANSISTOR CLASS C AMPLIFIER IS
(a)the lower modulation power is required
(b)higher power o/p per transistor
(c)better efficiency
(d)better linearity
Q13 AM IS USED FOR BROADCASTING BECAUSE
(A)it is more noise immune than other information system
(b)compared with other it requires less transmitting power
(c)its use avoids receiver complexity
(d)no other modulation system can provide the necessary bw for high fidelity
Q14 THE MOST COMMONLY USED FILTERS IN SSB GENERATIONS ARE
(A)mechanical
(b)rc
(c)lc
(d)low pass
Q15 IN AN SSB TRANSMITTER ONE IS MOST LIKELY TO FIND A
(a)class c audio amplifier
(b)tuned amplifier
(c)class b rf amplifier
(d)class a rf o/p amplifier
Q16 ONE OF THE FOLLOWING CANNOT BE USED TO REMOVE THE UNWANTED SIDEBAND IN SSB. THIS IS THE
(A)filter system
(b)phase shift method
(c)third method
(d)balanced modulator
Q17 IN THE SPECTRUM OF A FM WAVE
(a)the carrier frequency disappears when the modulation index is large
(b)the amplitude of any side band depends on the modulation index
(c)the total number of sidebands depends on the modulation index
(d)the carrier frequency cannot disappear
Q18 THE DIFFERENCE B/W PHASE N FREQUENCY MODULATION
(a)is purely theoretical because they are same in practice
(b)ia too great to make the two system compatible
(c)lies in the poorer audio response of phase modulation
(d)lies in different definitions of the modulation index
Q19 AN FM SIGNAL WITH MODULATION INDEX m IS PASSED THROUGH A FREQUENCY TRIPLER THE WAVE IN THE O/P OF THE TRIPLER WIILL HAVE A MODULATION INDEX OF
(A)m/3
(b)m
(c)3m
(d)9m
Q20 AN FM, SIGNAL WITH DEVIATION “a” IS PASSED THROUGH A MIXER N HAS ITS FREQUENCY REDUCED 5 FOLD .THE DEVIATION IN THE O/P OF THE MIXER IS
(a)5a
(b)indeterminate
(c)a/5
(d)a
Q21 A PRE EMPHASIS CIRCUIT PROVIDES EXTRA NOISE IMMUNITY BY
(a)boosting the base frequency
(b)amplifying the higher audio frequency
(c)pre amplifying the whole audio band
(d)converting the pm to fm
Q22 SINCE NOISE PM THE FM WAVE ,AS THE NOISE SIDEBAND FREQUENCY APPROACHES THE
CARRIER FREQUENCY ,THE NOISE AMPLITUDE
(a)remains constant
(b)decreases
(c)increases
(d)is equalised
Q23 WHEN THE MODULATING FREQUENCY IS DOUBLED ,THE MODULATION INDEX IS HALVED AND THE MODULATING VOLTAGE IS REMAINS CONSTANT,THE MODULATION SYSTEM IS
(a)am
(b)pm
(c)fm
(d)any of the three
Q24 INDICATE WHICH OF THE FOLLOWING IS NOT A ADVANTAGE OF FM OVER AM
(a)better noise immunity is provided
(b)lower bw is required
(c)the transmitted power is more useful
(d)less modulating power is required
Q25 ONE OF THE FOLLOWING IS INDIRECT WAY OF GENERATING FM IS THE
(a)reacatnce fet modulator
(b)varactor diode modulator
(c)armstrong method
(d)reactance bipolar transistor modulator
Q26 IN AN FM STEREO MULTIPLEXING TRANSMISSION ,THE
(a)sum signal modulates the 19 khz sun carrier
(b)difference signal modulates the 19 khz sub carrier
(c)difference signal modulates 38 khz sub carrier
(d)difference signal modulates 67 khz sub carrier
Q27 INDICATE WHICH OF THE FOLLOWING STATEMENTS ABOUT THE ADVANTAGE OF THE PHASE
DISCRIMINATOR OVER THE SLOPE DETECTOR IS FALSE
(a)much easier alignment
(b)better linearity
(c)greater limiting
(d)fewer tuned circuit
Q28 SHOW WHICH OF THE FOLLOWING STATEMENTS ABOUT THE AMPLITUDE LIMITER IS UNTRUE
(a)the circuit is always biased in class c ,by virtue of leak-type bias.
(b)when i/p increases past the threshold limiting the gain decreases to keep the o/p constant
(c)the o/p must be tuned
(d)leak type bias must be used
Q29 IN A RADIO RECEIVER WITH SIMPLE AGC
(a)an increase in signal strength produces more agc
(b)the audio stage gain is normally controlled by the agc
(c)the faster the agc time constant ,the more accurate the o/p
(d)the highest agc voltage is produced b/w stations
Q30 IN A BROADCAST SUPERHETRODYNE RECEIVER ,THE
(a)local oscillator operates below the signal frequency
(b)mixer i/p must be tuned to the signal frequency
(c)local oscillator frequency is normally doubled the if
(d) rf amplifier normally works at 455 khz above the carrier
Q31 TO PREVENT OVER LOADING OF THE LAST IF AMPLIFIER IN A RECEIVER ,ONE SHOULD USE
(A)squelch
(b)variable sensitivity
(c)variable selectivity
(d)double conversion
Q32 IN A RATIO DETECTOR
(a)the linearity is worse than in a phase discriminator
(b)stabilisation against signal strength variation is provided
(c)the o/p is twice obtainable from a similar phase discriminator
(d)the circuit is same as in a discriminator ,except that the diodes are reversed
Q33 THE TYPICAL SQUELACH CIRCUIT
(a)cuts off an audio amplifier when the carrier is absent
(b)eliminates the rf interference when the signsl is weak.
(c)cuts off an amplifier when the agc is maximum
(d)cuts off an amplifier when the agc is minimum
Q34 INDICATE THE FALSE STATEMENT IN CONNECTION WITH COMMUNICATION RECEIVERS
(a),the noise limiter cuts off the receiver’s o/p during a noise pulse
(b)a product demodulator could be used for the reception of morse code
(c)double conversions is used to improve image rejection
(d)variable sensitivity is used to eliminate selective fading
Q35 THE CONTROLLED OSCILLATOR SYNTHESIZER IS SOMETIMES PREFFERED TO THE DIRECT ONE BECAUSE
(a)it is a simpler piece of instrument
(b)it’s frequency stability is better
(c)it does not require crystal oscillator
(d)it is relatively free of spurious noise
Q35 THE FREQUENCY GENERATED BY EACH DECADE IN A DIRECT FREQUENCY SYNTHESIZER IS MUCH HIGHER THAN THE FREQUENCY SHOWN,THIS DONE TO
(A)reduce the spurious frequency problem
(b)increase the frequency stability of the synthesizer
(c)reduce the number of decades
(d)reduce the number of crystal required
Q36 INDICATE WHICH OF THE FOLLOWING CAN’T DEMODULATE SSB SIGNAL
(a)balanced modulator
(b)product modulator
(c)bfo
(d)phase discriminator
Q37 IF AN AMPLIFIER IS USED AS THE FIRST AF AMPLIFIER IN A TRANSISTOR RECEIVER ,THIS WILL HAVE THE EFFECT OF
(a)improving the effectiveness of the agc
(b)reducing the effect of -ve peak clipping
(c)reducing the effect of noise at low modulation depths
(d)improving the selectivity of the receiver
Q38 THE IMAGE FREQUENCY OF AN SUPERHETRODYNE RECEIVER IS
(a)is created within the receiver it self
(b)is due to insufficient adjacent channel rejection
(c)is not rejected by if tuned circuits
(d)is independent of the frequency at which the receiver is tuned
Q39 ONE OF THE MAIN FUNCTION OF THE RF AMPLIFIER IN SUPERHETRODYNE RECEIVER IS TO
(a)provide improve tracking
(b)permit better adjacent channel rejection
(c)increase the tuning range of the receiver
(d)improve the rejection of the image frequency
Q40 A RECEIVER HAS POOR IF SELECTIVITY.IT WILL THEREFORE ALSO HAVE POOR
(a)blocking
(b)double-spotting
(c)diversity reception
(d)sensitivity
Q41 THREE POINT TRACKING IS ACHIEVED WITH
(a)variable selectivity
(b)the padder capacitor
(c)double spotting
(d)double conversion
Q42 THE LOCAL OSCILLATOR OF A BROAD CAST RECEIVER IS TUNED TO O FREQUENCY HIGHER THAN THE INCOMING FREQUENCY
(a)to help the image frequency rejection
(b)to permit easier tracking
(c)because otherwise an intermediate frequency could not be produced
(d)to allow adequate frequency coverage without switching
Q43 A LOW RATIO OF THE AC TO THE DC LOAD IMPEDANCE OF A DIODE DETECTOR RESULTS IN
(a)diagonal clipping
(b)poor agc operation
(c)-ve peak clipping
(d)poor af response
Q44 THE INTERMEDIATE FREQUENCY IS VERY HIGH(INDICATE FALSE STATEMENT)
(a)image frequency rejection is very good
(b)the local oscillator need not be extremely stable
(c)the selectivity Will be poor
(d)tracking will be improved
Q45 WHEN A RECEIVER HAS A GOOD BLOCKING PERFORMANCE ,THIS MEANS THAT
(a)it does not suffer from double spotting
(b)it’s image frequency rejection is poor
(c)it is unaffected by agc derived from near by transmission
(d)it’s detector suffers from burnout
(A)a short circuit
(b)a complex impedance
(c)an open circuit
(d)a pure reactance
Q47 A(75-J50)ohm IS CONNECTED TO A COAXIAL LINE OF Z0=75 ohm AT 10GHZ .THE BEST WAY OF MATCHING CONSISTS IN CONNECTING
(a)a short circuit stab at the load
(b)an inductance at the load
(c)a capacitance at some specific distance from the load
(d)a short circuit stab at some specific distance from the load
Q48 THE VELOCITY FACTOR OF A TRANSMISSION LINE
(a)depends on the dielectric constant of the material used
(b)increases the velocity along the transmission line
(c)is governed by skin effect
(d)is higher for a solid dielectric than for air
Q49 IMPEDANCE INVERSION MAY BE OBTAINED WITH
(A)a short ckt stub
(B)an open ckt stub
(c)a quarter wave line
(d)a half wave line
Q50 SHORT CKT STUBS ARE PREFERRED TO OPEN CKT STUBS BECAUSE THE LATER ARE
(a)more difficult to make n connect
(b)made of transmission line of different characteristics impedance
(c)liable to radiate
(d)incapable of giving full range of reactances
