Online Electronics and Communication Engineering Test - Communication Systems Test 1

Instruction:

  • This is a FREE online test. Beware of scammers who ask for money to attend this test.
  • Total number of questions: 20.
  • Time allotted: 30 minutes.
  • Each question carries 1 mark; there are no negative marks.
  • DO NOT refresh the page.
  • All the best!

Marks : 2/20


Total number of questions
20
Number of answered questions
0
Number of unanswered questions
20
Test Review : View answers and explanation for this test.

1.
Which of the following has the highest input impedance?
CE
CB
CC
Push pull
Your Answer: Option
(Not Answered)
Correct Answer: Option
Explanation:

CC connection has very high input impedance and low output impedance.


2.
Consider the following statements
  1. The amplitude of an FM wave is constant
  2. FM is more immune to noise than AM
  3. FM broadcasts operate in upper VHF and UHF frequency ranges
  4. FM transmitting and receiving equipments are simpler as compared to AM transmitting and receiving equipments
Which of the above are correct?
1, 2, 3, 4
1, 2, 3
2, 3, 4
1, 3, 4
Your Answer: Option
(Not Answered)
Correct Answer: Option
Explanation:

FM equipments are complex as compared to AM equipments.


3.
In a high speed modem the data rate handled is about
1000 bps
5000 bps
20000 bps
50000 bps
Your Answer: Option
(Not Answered)
Correct Answer: Option
Explanation:

When data rate is in the range of 2400 to about 10800 bits per second, modem is designated as high speed.


4.
24 telephone channels, each band limited to 3.4 kHz are to be time division multiplexed using PCM. If sampling frequency is 10 kHz and number of quantization levels is 128, the required bandwidth of PCM is
1.68 MHz
240 kHz
81.6 kHz
3.072 MHz
Your Answer: Option
(Not Answered)
Correct Answer: Option
Explanation:

Bandwidth ≈ 24 (ln2 128) 10 kHz = 1.68 MHz.


5.
Some advantages of optical fibre cables are
  1. small diameter
  2. Immunity to cross talk and EM interference
  3. Laser and LED modulation methods lend themselves ideally to digital operation
Which of the above are correct?
1 only
1 and 2
1, 2, 3
2, 3
Your Answer: Option
(Not Answered)
Correct Answer: Option
Explanation:

Fibre optic cables have all these advantages.


6.
If the average power of radar transmitters is 2 kW and the peak power of the transmitter is 1000 kW, what will be the duty cycle?
0.002
0.02
0.001
0.01
Your Answer: Option
(Not Answered)
Correct Answer: Option
Explanation:

.


7.
A signal m(t) with bandwidth 500 Hz is first multiplied by a signal g(t) where . The resulting signal is then passes through an ideal low pass filter with bandwidth 1 kHz the output of the low pass filter would be
δ(t)
m(t)
0
m(t) δ(t)
Your Answer: Option
(Not Answered)
Correct Answer: Option
Explanation:

Multiplication in time domain is equivalent to convolution. According to the property of impulse signal, convolution of a signal m(t) with δ(t) is signal itself.

m(t) x g(t)

m(t).


8.
Consider the following functions
  1. It detects the AM video carrier IF so as to produce the video signal
  2. It produces and separates out the inter carrier sound IF of 5.5 MHz
  3. It amplifies the video signal
  4. It amplifies the audio signal
The video detector in a colour TV performs which of the above functions
1, 2 and 3
1, 2, 3 and 4
1 and 2
1, 2 and 4
Your Answer: Option
(Not Answered)
Correct Answer: Option
Explanation:

Video detector does not amplify any signal.


9.
Microwave link repeaters are typically 50 km apart in TV transmission due to
atmosphere attenuation
output power tube limitations
attenuation of surface wave
earth's curvature
Your Answer: Option
(Not Answered)
Correct Answer: Option
Explanation:

Earth's curvature limits line of sight distance. Therefore, repeaters are needed.


10.
In TV transmitter, the function of duplexer is
to amplify video signal
to remove distortions in audio signal
to combine outputs of visual and audio transmitters
to amplify audio signal
Your Answer: Option
(Not Answered)
Correct Answer: Option
Explanation:

Duplexer combines video and audio signals so that they can be sent out by a common antenna.


11.
The distance of a direct broadcasting satellite from earth's surface is about
1000 km
10000 km
36000 km
55000 km
Your Answer: Option
(Not Answered)
Correct Answer: Option

12.
An SSB-AM signal cannot be demodulated by
Balanced modulator
Complete phase shift generator
Diode balanced modulator
Product detector
Your Answer: Option
(Not Answered)
Correct Answer: Option

13.
For a three stage cascaded amplifier, having gains of G1, G2 and G3 and noise figures of F1, F2, F3 the overall noise figure
None of the above
Your Answer: Option
(Not Answered)
Correct Answer: Option

14.
Ground wave can be used for communication upto
5 kHz
12 kHz
16 kHz
25 kHz
Your Answer: Option
(Not Answered)
Correct Answer: Option

15.
In a hi-fi system the nonlinear distortion should be less than
10%
5%
2%
1%
Your Answer: Option
(Not Answered)
Correct Answer: Option

16.
In a colour TV receiver SAW filter consists of
piezoelectric substrate on which are deposited two inter, digital transducers
photo conductive substrate which are deposited two inter digital transducers
photo voltaic substrate which are deposited two inter digital transducers
photo resistive substrate which are deposited two inter digital transducers
Your Answer: Option
(Not Answered)
Correct Answer: Option

17.
A pulse width signal can be governed by
free running multi-vibrator
monostable multi-vibrator
Schmitt trigger
JK flip-flop
Your Answer: Option
(Not Answered)
Correct Answer: Option

18.
The number of spectral component when two sine wave of same frequency multiplied is
2
3
4
Your Answer: Option
(Not Answered)
Correct Answer: Option

19.
In a square law modulator, the carrier frequency should be __________ times than the highest modulating frequency.
1
2
4
3
Your Answer: Option
(Not Answered)
Correct Answer: Option

20.
In a FM receiver, amplitude limiter
amplifiers low frequency signals
reduces the amplitude of signals
eliminates any change in amplitude of received FM signals
none of the above
Your Answer: Option
(Not Answered)
Correct Answer: Option

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