Understanding Waves and Telecommunications: Radio, Phone & More
Waves and Communications
Waves are transmitted through various communication systems (radio, or our voice via telephony). A wave is a traveling space perturbation without the transport of matter, but with the transport of energy.
Features of Waves
- Period (T): The time it takes for one complete vibration.
- Frequency (f): The number of vibrations per second, equal to the inverse of the period: f = 1/T. Measured in s-1, also known as Hertz (Hz).
- Wavelength (λ): The distance between two consecutive peaks (highest points) or two consecutive valleys of a wave.
- Amplitude (A): The maximum displacement of a particle from its equilibrium position due to the wave. Amplitude is related to the energy transferred by the wave; a greater amplitude means greater energy transfer.
Types of Waves
- Mechanical Waves: Require a material medium to propagate. Examples include water waves, sound waves, and waves on a rope.
- Electromagnetic Waves: Can propagate through a vacuum and also through some material media. In 1887, Heinrich Hertz was the first to produce and detect electromagnetic waves.
The Electromagnetic Spectrum
The electromagnetic spectrum is the range of all possible electromagnetic wave frequencies. The applications of these waves depend on their wavelength:
- At one end of the spectrum are high-energy radiations like X-rays and gamma rays, which have smaller wavelengths and higher frequencies.
- In the intermediate range are radiations from ultraviolet light to infrared light, including the visible spectrum.
- At the other end are radio waves or radio frequencies, which have large wavelengths and low frequencies, used by various wireless communication systems (radio and microwaves).
The energy of radiation depends on its frequency; higher frequencies correspond to higher energy. Exposure to high-energy radiation can be dangerous to health.
Telecommunications
Telecommunications encompass various systems that use electricity to produce and quickly send visual, written, or voice messages. These include telegraphy, telephony, broadcasting, and television.
Telegraph and Radiotelegraphy
- Telegraph: The electric telegraph transmitted short or long electrical impulses through a cable to a receiver. An electromagnet and a clockwork mechanism moved a piece of paper, and a scoring pen marked stripes and points representing the message. The telegraph operator interpreted the telegram.
- Radiotelegraphy: Telegraphic transfers made by computer terminals connected to telephone networks, transmitting images, text, and digitally encoded data.
Telephone
A telephone consists of a base, a microphone, a headset (speaker), a keyboard, and a ringer. Modern phones contain a microchip that encodes and digitizes voice signals.
- Fixed (Landline): The earpiece and microphone are connected to the base by a cable, which connects to the telephone network.
- Wireless: Connected by radio waves at a short distance.
- Mobile (Cellular): A mobile phone has a radio transmitter and receiver in the microwave band. Signals travel from the phone to microwave antennas (including satellites), and then to another phone, which reconstructs the original sound.
Radio
In radio broadcasting, a radio station converts sound vibrations into electrical signals using a microphone. These signals are low frequency and cannot be transmitted directly because they would suffer interference and not reach distant locations. Transmission uses radio waves that are modified according to the electrical signals created in the microphone. This process is known as modulation.
AM (Amplitude Modulation) and FM (Frequency Modulation) radio waves have constant amplitude. Atmospheric interference is avoided due to changes in amplitude.