a. Atmospheric noise is caused by electrical discharges during lightning and thunderstorms. It falls in the frequency range from 1 kHz to 100 kHz. These electrical processes generate electromagnetic radiation that can interfere with radio communication.
b. Man-made noise, such as that generated by electrical machinery and appliances, can also interfere with radio communication. This includes electrical noise from power lines, electric motors, fluorescent lights, and other devices. These generate interference over a broad range of frequencies, from a few hundred hertz to several megahertz.
c. Noise from industrial sources, such as factories, construction sites, and transportation systems, can also contribute to terrestrial noise. Heavy machinery, drilling, and other activities generate noise that can interfere with radio signals.
d. Biological noise, such as bird calls and animal vocalizations, can also contribute to terrestrial noise. While bird calls typically have a limited frequency range, they can still interfere with certain types of radio communication.
Extra noise is a term used to describe all the noise and disturbances that are not generated in the receiving system. It includes:
a. Galactic noise, which is generated by astronomical objects such as stars, galaxies, and pulsars. This noise is particularly significant in the microwave range of the spectrum.
b. Solar noise, which is caused by disturbances on the sun's surface, such as solar flares and coronal mass ejections. Solar noise can significantly affect radio communication, particularly in the shortwave bands.
c. Extraterrestrial noise from sources beyond the solar system can also interfere with radio communication. These sources can include quasars, pulsars, and other celestial events that emit radio waves.
d. Artificial extraterrestrial noise, such as signals from satellites and other spacecraft, can also add to the extra noise.
The combined effect of terrestrial and extra noise can limit the sensitivity and performance of radio communication systems, making it difficult to receive weak signals and reducing the overall reliability and quality of communication.