The electromagnetic spectrum is a vast band of energy frequencies extending from radio waves to gamma waves. When you listen to the radio, watch TV, or cook dinner in a microwave oven, you are using electromagnetic waves. It is represented by frequency (in Hertz) or Wave length (in meter).
Spectrum is nothing but the band width of electromagnetic waves which is the difference between Upper and lower frequencies of the signal. Only a small portion of the spectrum, representing wavelengths of roughly 4x1014 - 7.5x1014 Hz, is visible to the human eye. The other regions are
Radio waves - less than 3x1011 Hz
Microwaves waves - 3x1011 – 1013 Hz
Infrared rays - 1x1013 - 4x1014 Hz
Visible rays - 4x1014 - 7.5x1014 Hz
Ultraviolet rays - 1015 – 1017 Hz
X-rays - 1017 – 1020 Hz
Gamma-rays - 1020 – 1024 Hz
This is represented in the following figure.
The frequencies less than 3x 1011 Hz (radio waves) are used to carry signals for radio, television and cellular phones. The region whose frequency is less than 3x 1011 Hz is called radio spectrum. So, spectrum is a frequency range in the electromagnetic region. We can cook food using micro wave oven which operates in the range 3x1011 – 1013 Hz. This is the spectrum of microwave.
The amount of bandwidth needed for 3G services could be as much as 15x106 to 20x106Hz (15 MHz – 20 MHz). Compare this with the bandwidth of 30x103 to 200x 103 Hz used for current 2G communication and you can see that there is as much as a 500-fold increase in the amount of bandwidth required.
The word spectrum refers to a collection of various types of electromagnetic radiations of different wavelengths. In India the radio frequencies are being used for different types of services like space communication, mobile communication, broadcasting, radio navigation, mobile satellite service, aeronautical satellite services, defence communication etc. Radio frequency is a natural resource but unlike other resources it will deplete when used. But it will be wasted if not used efficiently.
India’s National Frequency Allocation plan
The National Frequency Allocation Plan (NFAP) forms the basis for development and manufacturing of wireless equipment and spectrum utilization in the country. Frequency bands allocated to various types of radio services in India are as follows.
i) 0-87.5 MHz is used for marine and aeronautical navigation, short and medium wave radio, amateur (ham) radio and cordless phones.
ii) 87.5-108 MHz is used for FM radio broadcasts
iii)109- 173 Used for Satellite communication, aeronautical navigation and outdoor broadcast vans
iv) 174-230 MHz not allocated.
v)230—450 MHz Used for Satellite communication, aeronautical navigation and outdoor broadcast vans
vi) 450- 585 MHz. Not allocated.
vii) 585-698 MHz Used for TV broadcast
viii) 698-806 MHz not allocated.
ix) 806-960 MHz Used by GSM and CDMA mobile services
x) 960-1710 MHz Aeronautical and space communication
xi) 1710- 1930 MHz Used for GSM mobile services
xii) 1930-2010 MHz – Used by defence forces
xiii) 2010-2025 MHz – Not allocated
xiv) 2025-2110 MHz – Satellite and space communications
xv) 2110-2170 MHz – Not allocated
xvi) 2170-2300 MHz – Satellite and space communications
xvii) 2300-2400 MHz not allocated.
xviii) 2400- 2483.5 MHz Used for Wi-Fi and Bluetooth short range services
xix) 2483.5-3300 MHz Space communications
xx) 3300-3600 MHz not allocated.
xxi) 3600-10000 MHz Space research, radio navigation
xxii) 10000 MHz – used for satellite downlink for broadcast and DTH services
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