﻿ Engineering Entrance Exam Question and Answers | Communication Systems - Zigya

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# Communication Systems

#### Multiple Choice Questions

21.

A point-to-point communication mode is seen in

• satellite cable communication

• television transmission

• fax transmission

22.

If the heights of transmitting and the receiving antennas are each equal to h, the maximum line-of-sight distance between them is (R is the radius of the earth)

23.

A repeater is a combination of

24.

Find the mismatch

• Sky wave communication : Frequency upto 30 MHz

• Line of sight communication : Frequency greater than 40 MHz

• Mobile telephony : Frequency range 800 – 950 kHz

• Facsimile : Static document

25.

A television tower of height 140 m can broadcast its signal upto a maximum area of (Radius of earth = 6.4 x 106 m)

• 1.56 × 106 km2

• 5.6 × 103 km2

• 5.6 × 1010 km2

• 1.56 × 109 km2

26.

The waves that are bent down by the ionosphere are

• ground waves

• surface waves

• sky waves

• space waves

27.

A ground receiver in line-of-sight communication cannot receive direct waves due to

• its low frequency

• curvature of earth

• its high intensity

• smaller antenna

28.

In an amplitude modulation with modulation index 0.5, the ratio of the amplitude of the carrier wave to that of the side band in the modulated wave is

• 4 : 1

• 1 : 1

• 1 : 2

• 2 : 1

29.

The distance of coverage of a transmitting antenna is 12.8 km. Then, the height of the antenna is (Given that radius of earth = 6400 km)

• 6.4 m

• 12.8 m

• 3.2 m

• 16 m

30.

If Ec = 20 sin 10πt and Em = 10 sin 400 πt are carrier and modulating signals, the modulation index is

• 56 %

• 30 %

• 50 %

• 48 %