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.