Answer / ankurjha

FM is always better for sound as it is most noise immune.
AM is low BW & TV uses Vestigial Side Band Modulation (a
kind of AM, where thew BW is slightly more than single side
band)

Answer / visakh

Video signals have significant information content upto
frequencies of 4.5 MHz. So their BW is approx 4.5 MHz.
Hence if we use FM, the transmission BW becomes much
greater than 9 MHz according to Carson's rule. If AM is
used, the transmission BW is 9 MHz. Hence we actually
choose a variant of AM called VSB where by the BW obtained
is slightly greater than 4.5 MHz. Why VSB is chosen is
because if SSB is used, we need filters with ideal
characteristics to filter out a sideband which is not
practical.
FM is used for audio because:
1. Higher noise immunity because FM is not affected by
amplitude variations.
2. The BW allotted to each FM broadcasting station is
200KHz whereas it is 10KHz for AM. The audio frequency
range is from 20Hz- 20KHz. So using FM we can reproduce all
the audio frequencies giving hence giving better clarity.

Answer / ishant

in fm there is a phase change which can be easily detected
by human eyes hence this will degrade the quality of video
.so vsb is used for video.and phase change does not create a
trouble for audio. hence audio signals are mostly sent
through fm.


ISHANT JAIN
G.L.A UNIVERSITY,MATHURA

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