In the next lesson, we shall learn about Atmospheric, Reflection and Static Attenuation. We had understood about Surface Attenuation in our earlier post.
ATMOSPHERIC ATTENUATION
Atmospheric Attenuation causes weakening of Radio Waves due to Atmospheric Absorption, Reflection Attenuation and Static Interference. Atmospheric Absorption or Scattering of Radio waves are caused by small particles in atmosphere. Higher frequency Radio Waves are affected more by Atmospheric Absorption. Frequencies in 5 Gigahertz band are affected badly by absorption.
The wavelength in these frequency bands would be approximately between 10 to 1 MM. Since these wavelengths are almost the same as size of water droplets in the clouds, this frequency band affected the most due to affected by atmospheric absorption and attenuation.
REFLECTION – STATIC ATTENUATION
Reflection Attenuation is caused due reflections from buildings and hills. In order to reduce reflection attenuation, we have seen antennas being mounted on tall masts or on top of hills.
Static interference is caused due to negative charges in atmosphere. These static charges build up due to Rain, Thunderstorm or Solar Activity. Static interference is higher in lower frequencies affecting voice clarity. At times, equipment’s electronic circuits also cause Static Interference.
SIGNAL – NOISE RATIO
Signal to noise ratio is the ratio of strength of signal to static noise levels measured in decibels. Better signal to noise ratio is achieved by either increasing transmission power as per inverse square law which states that doubling the range requires four times increase in power.
Another way of increasing the signal to noise ratio is by or by improving the sensitivity of our receiver. This can be done by improving the electronics inside the receiver enabling it to reduce the internal noise and process weaker signals.
Having learnt about the different types of attenuation, let us learn about Diffraction of Radio Waves in the next post.