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FM AND AM
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COMPARISON OF AM AND FM
NO. FM AM
1. Amplitude of FM wave is
constant and independent of
modulation index
Amplitude of AM wave is
varying and dependent of
modulation index
2. So transmitted power remains
constant and independent of
modulation index
So transmitted power
dependent on modulation
index
3. No. of sidebands having
significant amplitude depends
on modulation index
No. of sidebands will be
constant and 2 sidebands
4. FM receivers are immune to
noise
AM receivers are not immune
to noise
5. Bandwidth=2(fm+Δf) Bandwidth=2fm
6. Bandwidth is large. Hence
wide channel is required.
Bandwidth is less than FM.
7. Space wave is used for
propagation. So radius of
transmission is limited to
LOS.
Ground and sky wave
propagation used. Large area
coverage
8. FM transmission and
reception equipments are
complex.
AM transmission and
reception equipments are less
complex.
9. Information is carried in the
frequency variation of the
carrier.
Information is carried in the
amplitude variation of the
carrier.
10. Eg:-Radio and TV
broadcasting, police and
Radio and TV broadcasting
wireless, point to point
communications
No.
Parameter PAM PWM PPM
1 Waveform
2 Variation parameter
Amplitude Width Position
3 Bandwidth required
Less
Bandwidth of transmission channel depends on width of pulse
High
depends on risetime of pulse
High
depends on width of pulse
4 Noise immunity
Low High High
5 Transmitted power
Varies with amplitude of pulse
Varies with width of pulse
Remains constant
6 Need for synchronization pulse
No No Yes
7 System Complex Simple to implement Simple to implement8 Complexity
of generation and detection
Less More More
9 Similar to AM modulation
FM modulation PM modulation
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