Introduction:-
Radio Frequency (rf) transmission is a wireless technology. The various ranges of frequency used the transmission come under the radio frequency spectrum spanning from 30 Hz to 300 GHz; typically , 10 kHz to 100 GHz for a long wave , short wave and microwave radio transmission.
Working:-
RF transmission uses radio waves like radio or television signals to transmit audio via a carrier from a transmitter to a receiver. Like a radio station transmitter the transmitter has an antenna usually attached to the transmitter unit which needs to be positioned to adequately cover the listening area. Small hand held portable transmitter usually with have a built-in antenna. The receiver units are either single channel or multichannel and they receive the modulated radio waves and convert them back into an audio signal which is sent to the headphone output. Multi-channel receivers will have a channel selector which allows a user to select a specific transmission channel.
RF transmission can be categorized as follows depending upon the medium through which RF signals propagates :
1. Free space propagation: Signals travel in free space. Signals travelling to and from satellites use this type of radio propagation.
2. Ground wave propagation: When signals travel via ground wave these tend to follow the earth's curvature. Medium-wave bend uses this form of propagation.
3. Ionospheric propagation: Radio signal propagation through ionosphere is used by stations on short-wave is used by stations on short wave bands for their signals to heard around the globe.
4. Tropospheric propagation: In this form of radio propagation, RF signals are transmitted in the troposhere just above the earth's surface.
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