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2. Radio Waves

Radio waves use radio frequencies which are
allocated to private businesses for direct voice
communication. A radio set-up uses transmitter
and receiver. A transmitter sends radio waves
and encodes them into sine waves which, when
received by a receiver, are decoded and the
message is received. Both the transmitter and
receiver use antennas to radiate and fetch radio
signals. They are not line-of-sight transmission
and, hence, can penetrate buildings easily.
Fig. 8.30: Radio Waves
Advantages of Radio Waves

(a) They can be used indoors or outdoors.
(b) They are omnidirectional and can travel in any direction.

(c) Transmitter and receiver antenna do not need to be physically aligned.
(d) Radio wave transmission offers mobility.
(e) It is cheaper than laying cables and fibres.

(f) It offers ease of communication over difficult terrain.
Disadvantages of Radio Waves

(a) Radio wave communication is an insecure mode of communication.

(b) Radio wave propagation is susceptible to weather effects like rain, thunderstorm, etc.
3. Satellite Link

Satellite transmission is also a kind of
line-of-sight transmission that is used
to transmit signals throughout the
world. When the frequency is greater
than 3 GHz, the transmission is known
as microwave. Satellite is a special
type of microwave transmission
medium.
It provides various types of services Fig. 8.31: Satellite Link
Computer Science with Python–XII 8.28 antenna to transmit and receive data from satellites.
such as transmitting fax, voice data,
video, email and other internet
applications. In satellite communication, an earth station has a satellite dish, which functions as an

When data is transmitted from an earth station to a satellite, it is known as uplink and when
transmission takes place from a satellite to an earth station, it is known as downlink. In satellite,
there are transponders that send and receive signals from/to the earth station.