Introduction to RF communication

Now a days, we are surrounded by a large number of wireless devices working on different protocols, on different frequency bands thus utilizing almost whole of the “Radio-wave” frequency spectrum.

Adhering to it’s high density, complete frequency spectrum can be divided into different groups and each group can be further divided into different channels.

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Considering the above distribution, most of the wireless devices works in the VHF and UHF bands. Working on such high frequencies has some of it’s renowned advantages like decreased antenna size, low interference from power devices, efficiency in propagation (low dispersion) etc.
Propagation at lower frequencies reduces dependencies on line-of-sight communication (As they get reflected from ionosphere). They are characterized by narrow bandwidth(usually 10%), higher bandwidths might reduce performance.
VLF and LF links usually carry low-rate digital signals or Morse code, while MF links are wide enough to carry voice signals. Above approximately 30 MHz, radio transmissions pass through the ionosphere, so higher frequency signals cannot propagate through ionospheric hops. They operate on line-of-sight or near line-of-sight propagation paths.
VHF and UHF support enough bandwidth to carry not only voice and data, but also video signals—including commercial television broadcasts.
Microwave frequencies are used to carry high information content signals in wide bandwidths. Wide band microwave point-to-point links carry large blocks of telephone signals, television signals, and wide band digital data. Communication satellite links are also at microwave.

For analysis of frequency domain, we usually prefer decibel scale since it allows a wide range of frequency components to be represented on a single scale!

Availability of frequency bands in India