D. C. Pandey Solutions for Chapter: Basics of Communications, Exercise 23: Objective Problems [Level 2]

The waves used for Line of Sight (LOS) communication are

A radar has a power of $1 \mathrm{kW}$ and is operating at a frequency of $10 \mathrm{GHz}$. It is located on a mountain top of height $500 \mathrm{m}$. The maximum distance up to which it can detect object located on the surface of the earth (radius of the earth$=6.4\times {10}^6 \mathrm{m}$) is,

Which of the following four alternatives is not correct? We need modulation,

This question has Statement I and Statement II. Of the four choices given after the statements, choose the one that best describes the two statements.

Statement I: Sky wave signals are used for long distance radio communication. These signals are in general, less stable than ground wave signals.

Statement II: The state of ionosphere varies from hour to hour, day to day and season to season.

If $E_{\mathrm{c}}=20\sin {10}^5\pi t$ and $E_{\mathrm{m}}=10\sin 400\pi t$  are carrier and modulating signals respectively, the modulation index is

$1000\mathrm{kHz}$ carrier wave is amplitude modulated by the signal frequency $200 \mathrm{Hz}-4000 \mathrm{Hz}$. The channel width of this case is

The distance of coverage of a transmitting antenna is $12.8 \mathrm{km}$. Then, the height of the antenna is (given that radius of the earth$=6400 \mathrm{km}$),

Which one of the following is incorrect statement in the transmission of electromagnetic waves?