STES's

Smt. Kashibai Navale College of Engineering, Vadgaon, Pune

Department of E &TC Engineering
MCQ : Principles of Communication Systems
UNIT-II : AM transmission & Reception for Signal Tone

Sr. No Question Option A Option B Option C Option D Correct Option

Modulation is a process of ---------- modulating signal on
1 adding dividing subtracting superimposing d
carrier signal
In AM, if modulating signal and carrier signal are same
2 0 100 50 33 b
then modulation index is ----%
In AM if over modulation occurs then modulation index is
3 greater than equal to less than none a
--- one
dependents on
4 In AM signal, amplitude of sidebands is ----- dependent on carrier both A & B None a
modulation index
5 The major advantage of DSBSC is decrease in BW power saving less modulation index all b
The relation between carrier power and total power in an
6 Pc=Pt(1+m2/4) Pc=Pt(1+m2/2) Pt=Pc(1+m2/4) Pt=Pc(1+m2/2) b
AM wav is
7 Bandwidth of voice signal is----- 3.1KHz 3.4KHz 5MHz 15KHz a

8 A role of modulating frequency in AM is to decide ----- Bandwidth Sidebands power modulation index a
Baseband communication refers to transmission of
9 without modulation with modulation with multiplication None a
baseband signal
10 Disadvantage of SSBSC is more power more BW difficult to retrieve All c

11 synchronous detection is used for demodulation of DSB-SC DSB-FC VSB-FC None a

Amplitude modulation is defined as a system of Amplitude of carrier is Amplitude of carrier is Amplitude of message Amplitude of message
12 b
modulation in which varied in accordance varied in accordance is varied in accordance is varied in accordance
13 The frequency range of voice signal is given by 300Hz -3.4KHz 0-5MHz 20Hz-20KHz 20Hz-15 KHz a

14 The output of analog multiplier is 0 to 1 . -1 to 1 0 to ∞ .-∞ to ∞ a

15 The output of analog multiplier is AM DSBSC SSB VSB a

 STES's
Smt. Kashibai Navale College of Engineering, Vadgaon, Pune
Department of E &TC Engineering
MCQ : Principles of Communication Systems
UNIT-II : AM transmission & Reception for Signal Tone

Sr. No Question Option A Option B Option C Option D Correct Option

Local oscilator frequency should be ___than signal
16 higher than lower than equal to none of above a
frequency.
The original modulating signal is recovered back from
17 tracking modulation demodulation none c
AM signal by the process of______
18 Tracking error is negetive in______tarcking. padder trimmer 3 point none of above b
The image rejection is____if we choose a low value
19 improoved poor unaffected None of above b
of IF.
A____clipping occur when modulaion index on the output
20 diagonal none boh a and d negative feedback d
side of detector is higher than on its input side.

21 Envelop detection is used for DSB-FC DSB-SC VSB All of above a

22 Intermediate frequency for AM receiver is _________. 450 kHz 455MHz 455kHz 450MHz c
Improves the adjacent Helps in image signal Makes it easier to align Improves the fidelity
23 An RF amplifier of a superheterodyne receiver b
channel selectivity suppression the receiver of the receiver
Is created within the Is due to insufficient Is not rejected by the Is independent of the
24 The image frequency of a superheterodyne receiver c
receiver itself adjacent channel IF tuned circuits frequency to which the
Maintain the carrier Maintain the carrier Improve selectivity of Improve noise figure
25 AGC is used in a radio receiver to a
level at the second level at the second the receiver of the receiver
reduces adjacent increases tracking
26 High intermediate frequency in a superhet receiver improves selectivity none d
channel rejection problem
27 Padder tracking is------- point tracking two three one none a

28 Envelope detection is used for VSB DSB-SC DSB-FC all of these c

In trimmer tracking , trimmer capacitor is connected in -----
29 series parallel Both (a) & (b) none b
--- with main capacitor C.
30 AGC controls the gain of ------------- amplifiers Audio and IF RF RF and audio RF and IF d
 STES's
Smt. Kashibai Navale College of Engineering, Vadgaon, Pune
Department of E &TC Engineering
MCQ : Principles of Communication Systems
UNIT-II : AM transmission & Reception for Signal Tone

Sr. No Question Option A Option B Option C Option D Correct Option

if modulating signal has frequency of 10KHz then
31 20 10 5 0 a
bandwidth of AM is ---- KHz
32 The maximum power in DSBFC signal is 1.25Pc 1.5Pc 1Pc None b

33 The expression for total power in SSB wave is Pc /8 Pc /4 Pc /2 Pc b

If modulating signal is song signal with frequency
34 between 1KHz to 5KHz then bandwidth of AM is ---- 8 10 4 5 a
KHz
35 For a trapezoidal pattern modulation index is given as X+Y/X-Y X+Y/2(X-Y) X-Y/2(X+Y) X-Y/X+Y d

36 Bandwidth of an ISB signal is fm1+fm2 fm1-fm2 2(fm1) 2(fm2) a

37 The bandwidth of SSB wave is given by fc+fm fc-fm fm fc c

one sideband and
38 The VSB wave will have carrier, LSB and USB. LSB and USB LSB or USB d
voltage of other
Analog or digital
39 Baseband signals can be Only digital signals Only Analog signals None of above c
signals
To transmit baseband signal of frequency 15KHzdirectlt
40 7500 5000 50 1000 b
antenna height required is -----meters

41 One of the following cannot be used for SSB generation Filter method Phase shift method Third method Balanced Modulator d
Amplitude modulation generated at very low voltage or
42 High level modulation Low level modulation Collector modulation Grid modulation b
power is called as
In phase shift method of SSB generation either sideband is
43 Sharp selectivity Carrier suppression Phase shift Phase inversion d
cancelled out because of
A -------------is used to describe the range of frequencies
44 Bandwidth Channel Bandwidth Wavelength None of these b
required to transmit the desired information
fc>>fm, the frequency of VSB wave can be approximated
45 Fc Fm (fc-fm)/2 (fc+fm)/2 a
by
 STES's
Smt. Kashibai Navale College of Engineering, Vadgaon, Pune
Department of E &TC Engineering
MCQ : Principles of Communication Systems
UNIT-II : AM transmission & Reception for Signal Tone

Sr. No Question Option A Option B Option C Option D Correct Option

46 RF carrier range for MW band is __________. 535 kHz to 1650 kHz 5 to 10 MHz 435 kHz to 1500 kHz 1500 kHz to 1700 kHz a
A receiver has a desired input signal of 18MHz and an LO
47 18MHz 1.6MHZ 19.6MHz 21.2MHz b
frequency of 19.6MHz .The image frequency is--------
envelope distortion and
48 Error in synchronous detection is frequency and phase both (a) & (b) none b
diagonal clipping
If two frequency components f1 & f2 are mixed in a mixer
49 then the mixer output consist of components ---- if f1 f2(f1-f2) f1+f2 All of above d
(f1>f2).
A superheterodyne receiver is tuned at 1000khz. If the IF
50 1000khz 450 1900khz 1450khz c
is 450 khz the image frequency.
modulation index on the
.RC time constant of load
51 Diagonal clipping occurs when---------- output side of detector is Both (a) & (b) none a
circuit is too lone
higher than on its input
modulation index RC time constant amplification factor
52 To estimate the distortion choose -------- none b
properly properly properly
A -------- IF can make selectivity too sharp cutting the
53 low high very low very high c
sidebands
Clipping occurs when modulation index on the output side
54 diagonal negative peak Both (a) & (b) none b
of detector is higher than on its input side.
The---- detector is used in all the commercial AM
55 rectifier switching envelope none c
receivers.
56 A BFO is required to detect-------------- signal SSBSC FM DSB-FC All of above a

57 The receiver is most popular and widely used receiver TRF Superheterodyne communication all of these b
Sensitivity of a receiver depends upon the receivers
58 Bandwidth gain selectivity Noise response b
overall-------
The stage contributing significantly to the sensitivity of a
59 The mixer stage The RF stage Detector stage The IF stage d
superheterodyne AM broadcast receiver, is the
One of the main functions of the RF amplifier in a Provide improved Permit better adjacent Improve the rejection of Increase the tuning range
60 c
superheterodyne receiver is to tracking channel rejection the image frequency. of the receiver
 STES's
Smt. Kashibai Navale College of Engineering, Vadgaon, Pune
Department of E &TC Engineering
MCQ : Principles of Communication Systems
UNIT-II : AM transmission & Reception for Signal Tone

Sr. No Question Option A Option B Option C Option D Correct Option

In AM, if modulating signal has 1V amplitude with 5KHz

61 and carrier signals has amplitude 2V with frequency 100 0 100 50 25 c
KHz then modulation index is ---%

A 400W carrier is modulated at the depth of 75% then

62 400 512.5 300 200 b
power in AM is ----
63 Height of antenna if carrier frequency is 1MHz is ---mts 750 75 1 1000 b
At m = 1, Percentage power saving when carrier and one
64 83.33 66.67 33.34 none a
of the sideband suppressed is -----
An Antenna current of AM Transmitters modulated depth
65 of 40% by an audio wave is 11Amp. It increases 12 Amp. 40 75.7 64.3 None of these b
As a result of simultaneous modulated by another wave,

206.896Hz, 175.065
Modulating signal m(t) is given by 254.64Hz, 222.81Hz,
Hz, 159.15Hz, 254.64Hz and 254.64 Hz, 159.15Hz,
66 m(t)=COS(100t)*COS(500t) then what will be the 159.15Hz, 95.49Hz a
frequency components in 2*m(t)*COS(1000t) spectrum
143.235Hz and 63.66Hz 95.49Hz and 63.66Hz.
and 63.66Hz
11.404Hz.
If two simultaneous sine waves are modulated at the depth
67 of 30% and 40% with 1KW carrier power, then total 62.5 125 1.125K 1.0625K a
power in upper
In AM,DSBFC if +Vmax=16V & +Vmin=4V, peak
68 20 V 2V 15 V 10 V d
amplitude of carrier is ---
998.0 KHz, 999.2
100 KHz,1800
A 1000KHz carrier is simultaneously modulated by KHz, 999.7 KHz,
1000KHz ,300Hz, 1800 KHz,1300 KHz KHz,700 KHz,1300
69 300Hz, 800Hz and 2KHz audio sine waves. The 1000KHz,1000. 3KHz d
frequencies present in the output will be
800Hz and 2KHz and 1002 KHz KHz,1002 KHz,998
,1000.8 KHz
KHz and 1000 KHz
and1002.0 KHz
A broadcast radio transmitter radiates 10KW when
70 modulation percentage is 60. then the carrier power 10 8.47 6 None b
will be ---- KW
 STES's
Smt. Kashibai Navale College of Engineering, Vadgaon, Pune
Department of E &TC Engineering
MCQ : Principles of Communication Systems
UNIT-II : AM transmission & Reception for Signal Tone

Sr. No Question Option A Option B Option C Option D Correct Option

71 The tracking error is zero at_________. 600khz 950khz 1500khz All of above d
What will be image frequency for above example if carrier
72 30MHz 10Mhz 25MHz 5MHz a
frequency of incoming signal is 20MHz

A superheterodyne receiver with an IF of 450 KHz is

73 2400KHz 900KHz 1650KHz 2100KHz d
tuned to a signal at 1200 kHz. The image frequency is
If local oscillator frequency is designed to be lower than
74 995KHz to 2105 KHz 85KHz to 1195 KHz none both (a) & (b) b
signal frequency than fo will be in the range.
A superheterodyne receiver with an IF of 450kHz is tuned
75 2100kHz 750kHz 900kHz 1650kHz a
to a signal at 1200kHz. The image frequency is
If local oscillator frequency is designed to be lower
76 995khz to 2105khz 85khz to 1195 khz none of above all b
than signal the f0 will be in the range.
For DSB-SC system expensive circuitry is required for received signal is at low synchronous detection is local carrier generation is
77 none of above b
detection of original signal because power level required difficult
Enable us to cover the
Produce the correct required tuning range
In an AM broadcast superheterodyne receiver , the local intermediate frequency, with the practically
Provide better image
78 oscillator frequency is arranged to be higher Than the Make tracking easier since a lower LO possible ratio of d
rejection
incoming signal frequency in order to frequency will not permit maximum to minimum
generation of correct IF. values of the variable
capacitors.
The principle of----------- states that input modulated
79 signal is multiplied with a locally generated phase and synchronous detection envelope detection none of these both (a) & (b) a
frequency synchronous carrier at the receiver.
The AM broadcast receiver has an IF of 465kHz & is
80 1465khz 1930khz 535khz None of above b
tuned to 1000khz then the image frequency is