Communication Systems

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Question
CBSEENPH12039404

Which mode of propagation is used by short wave broadcast services?

Solution

Skywave is used to propagate shortwave broadcast services.

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Question
CBSEENPH12039411

A carrier wave of peak voltage 15 V is used to transmit a message signal. Find the peak voltage of the modulating signal in order to have a modulation index of 60%.

Solution

It is given that peak voltage of carrier wave, Ac = 15V

and, Modulation index, mu = 60% = 60/100

Then, the peak voltage of the modulating signal (Am) will be given by the relation,

μ = AmAc60% = 15 VAcAc =1560 x 100 = 25 V

Question
CBSEENPH12039431

Give three reasons why the modulation of a message signal is necessary for long-distance transmission.

Solution

Reasons:

  1. Height of antenna
  2. Power of signal
  3. Utilization of frequency

Question
CBSEENPH12039432

Show graphically an audio signal, a carrier wave and an amplitude modulated wave.

Solution

Audio Signal: