Introduction of Waves: Communication with Radio Waves

Waves

Every communication system has three essential elements.

• Transmitter
• Channel
• Receiver

Explanation:

The first step of communication is to convert the message signal produced by the source into a form suitable for transmission through the channel. If the output of the information source is a non-electrical signal like a voice signal, a transducer converts it to an electrical form before giving it as an input to the transmitter.

When a transmitted signal propagates along the channel, it may get distorted due to channel imperfection. Moreover, noise adds to the transmitted signal, and the receiver receives a corrupted version of the transmitted signal.

The receiver has the task of operating on the received signal. It reconstructs a recognizable form of the original message signal for delivering it to the user of information.

Communication Using Radio Waves:

In communication using radio waves, an antenna at the transmitter radiates electromagnetic waves, which travel through space and reach the receiving antenna at the other end.

We use electromagnetic waves each time when we talk on the telephone, listen to the radio, watch TV, or do research on the internet. Today we can talk to someone far away or send an email almost instantly.

Telecommunication:

Communication with electromagnetic waves is called telecommunication. Radio waves are used to send and receive information over long distances. Using radio waves to communicate has several advantages. Radio waves pass through walls and windows easily.

They are not harmful to people like X-rays and ultraviolet waves are. So, most telecommunication devices like radios, TVs, and telephones use radio waves to send and receive sounds and images. Radio waves are used as carrier waves to broadcast signals by a station at their assigned frequency.  Radio and TV stations are given a frequency at which they broadcast radio waves.

Modulation:

We cannot send signal frequency (audio waves) at long distances. The process of superimposing signal frequency (i.e., audio wave) on the carrier wave is known as modulation. Radio waves are used as carrier waves to broadcast signals by a station at their assigned frequency. Radio and TV stations are given a frequency at which they broadcast radio waves.

To receive the broadcasted signal, we tune our radio or TV to the frequency of the station’s carrier waves. The amplitude or frequency of the carrier wave is changed to send information.

Amplitude Modulation:

The letters AM in AM radio stand for amplitude modulation. The amplitude of the carrier wave is changed to send information. The original sound is changed into an electrical signal. The electrical signal is used to vary the amplitude of the carrier wave, as shown in the figure.

In amplitude modulation, the frequency of the carrier wave does not change; only the amplitude changes. In the receiver, the varying amplitude of the carrier waves produces an electrical signal. The radio’s loudspeaker uses the signal to produce the original sound.

Frequency Modulation:

FM stands for frequency modulation. FM radio works much the same way as AM radio. The frequency of the carrier wave is changed, as shown in the figure. The FM receiver uses the varying frequency of the carrier wave to produce an electrical signal. The radio’s speaker converts the electrical signal into sound waves.

Telephones:

Telephones change a sound wave into an electric signal. The signal travels through a wire to the telephone switching system. The electrical signals may be sent through wires or changed to radio or microwave signals and sent through the air. The electrical signal may also be changed to a light wave to be sent through fiber-optic cables. At the receiving end, the signal is changed back to sound waves.

Wireless Phones:

Many phones do not use wires to send signals. Some use radio waves. Cordless phones change the electrical signal from the microphone of a telephone into a radio signal. The signal is sent to the base station of the telephone. If we are receiving a call on a cordless telephone, the base station sends electrical signals to the phone. The phone changes the electrical signals into sound waves.

Cellular Phones:

If we are receiving a call on a cellular phone, the base station sends electrical signals to the phone. The phone changes the electrical signals into sound waves. A cellular phone works over distances of many kilometers. The base station uses a large antenna. The antenna communicates with the cell phone and with other base stations.

Satellite Communication:

Radio signals cannot travel directly through Earth. Instead, radio signals are sent to the satellite. This type of communication is known as satellite communication. The satellite can communicate with other satellites or with ground stations.

The Global Positioning System:

The Global Positioning System, or GPS, is a system of the ground station, satellites, and receivers that are used to locate objects on Earth. A GPS receiver measures the time it takes for radio waves to travel from several satellites to the receiver. The receiver uses this information to find its latitude, longitude, and elevation.