External Noise

External Noise :

• It is external to the communication equipment like radio receiver ,television ,telephone ,etc…
• External nose are uncontrollable at a given geographical location.
• External noise can be further classified into three types as follows.

1. Atmospheric Noise
2. Extraterrestrial Noise
3. Solar Noise

a.Atmospheric Noise :

• Atmospheric noise is radio noise caused by natural atmospheric processes, primarily lightning discharges in thunderstorm.
• Atmospheric noise is commonly called static electricity noise.
• Atmospheric noise has wide range of frequency hence it has large bandwidth.
• Amplitude of this noise is inversely proportional to the frequency.

b.Extra-terrestrial Noise :

• Noise consists of electrical signals that originate from outside Earth’s atmosphere.
• It is sometimes called as deep space noise.
• It has frequency range from 8MHz to 1.43GHz.
• Extraterrestrial nose can be divided into two categories.
• Solar Noise
• Cosmic Noise

Solar Noise :

• Source of this noise is sun.
• This noise is generated due to constant radiation from sun at high temperature.
• Spectrum of this radiation is broad and interferes with communication channels.
• Magnitude of this noise changes with time.

Cosmic Noise :

• Source of this noise is stars.
• These stars are at large distance and they have also high temperature due to which they are radiating cosmic noise.
• Cosmic noise uniformly distributed over entire sky and uniformly distributed over frequency spectrum
• If we receive it from galaxy, it is known as galactic noise.

c.Industrial Noise 犀利士
:

• Source of industrial noise are automobile-air craft ignition,electric motor-switch gears, fluorescent light,etc.. a
• It is man-made noise.