Terrestrial TV Reception Systems: Components and Functionality

Systems Receiving Terrestrial Television

A TV reception system is the set of mechanical and electronic devices responsible for receiving television signals and transmitting them to a television receiver in good physical condition.

Collective Antenna Systems

In collective antenna systems, the following components are used:

• Antennas
• Preamplifiers
• Broadband amplifiers
• Monochannel amplifiers
• Converters and modulators
• Filters
• Attenuators
• Mixers
• Equalizers
• Splitters
• Taps
• Plugs
• Junction boxes
• Coaxial cable

Parts of an Aerial Installation

1. Signal Sensor System: A set of devices that receive the signals that are transmitted over the air. They are located on the outside and are composed of antennas and preamplifiers.
2. Headend Equipment: Receives signals from sensor systems and adapts them for distribution according to the required quality requirements. It is located within the building and consists of broadband and monochannel amplifiers, converters, modulators, filters, mixers, and equalizers.
3. Distribution Network: Collects the output signals of the headend equipment and distributes them to user outlets. The installation is located throughout the building and consists of splitters, shunts, and end-of-line outlets.

Materials for the Signal Sensor System

A TV antenna must meet the following requirements:

1. Receive the signal well.
2. Avoid picking up signals reflected in buildings or mountains.
3. Avoid reflections of signals in the system.
4. Capture the lowest possible interference.
5. Be useful for multiple channels.

Most Important Parameters

• Directivity: The capability of an antenna to concentrate radiated power in a certain direction of space.
• Gain: The relationship between the power received or delivered to a load circuit connected to the antenna and the received power at the same circuit with a reference antenna now oriented, giving the same result as the previous case. Its unit is dB.
• Bandwidth: The frequency range within which the antenna maintains its gain characteristics.

Yagi Antenna

Formed by a sensor element called a dipole, a reflector, and one or several directors. The dipole's function is capturing the signal. The reflector prevents, to a greater or lesser extent, subsequent reception and reinforces the previous one. The directors narrow the beam or receiving lobe while prolonging it.

Panel Antenna

This structure has an even number of separate dipoles that align themselves so that the effects of the dipoles combine, obtaining an average profit and a good bandwidth.

Preamplifiers

Their use is not always necessary and depends on the TV signal conditions.

Headend Equipment Materials

Amplifiers

Devices that increase the level of the existing signal. They can be divided into two types: monochannel amplifiers and broadband amplifiers.

Converters

Devices that allow the passage of broadcasts from one channel to another.

Modulators

Devices that allow signals from video and audio input to generate a modulated signal in an RF channel.

Mixer

A device designed to receive TV signals from its various inputs and channel them to exit via a single cable. Characteristics are good adaptation at the entrances and exits, low losses, and rejection at the outputs.

Filters

A device designed to select certain frequencies.

Attenuators

Elements intended to produce a decrease or attenuation of the signal at the facility where they are inserted. They are used to balance signals to avoid saturation in the amplifiers.

Equalizers

Electronic devices responsible for balancing the output levels of the signals on the inputs. They are used in facilities with different signal levels, allowing even levels.

Materials of the Distribution Network

Distributors

Devices that distribute the input signal into multiple outputs, allowing the generation of several lines of descent from a single input. Most important parameters: Attenuation (dB), input/output adaptation (VSWR), and rejection between outputs (dB).

Shunts

Devices that produce one or more branches in a distribution line by taking down part of the signal flowing through it, hardly affecting it. Features: shunt attenuation (dB), step attenuation (dB), and rejection between outputs (dB).

Outlets and End-of-Line Outlets

Elements that allow the user to obtain the signal line to apply to the TV's input. Features are the same as the previous ones.