Satellite TV Installation and Reception: A Comprehensive Guide
Installation of Satellite TV Reception
This allows you to receive many channels on a TV set. The repeater or relay transmitter for the TV signal used is an artificial satellite placed in space at a certain height above ground. A satellite TV system consists of: a ground station radio, a satellite, and a ground receiving station.
Satellite TV: General Concepts
Geostationary Orbit: This is where the satellite is placed after its launch. It describes a circle around the Earth in parallel with the Equator, rotating in the same direction and at the same angular velocity as the Earth. This rotation ensures that the satellite remains in the same position relative to a given location on Earth’s surface.
Satellite Orbital Position: This is the angle formed at the center of the Earth from a reference point on the Equator and the satellite.
Satellites: Constituents
There are two main parts:
- Service Modules: This part of the satellite is equipped with all the elements necessary for its proper functioning.
- Telecommunications Module: This consists of all the elements necessary to provide the satellite TV service. It comprises:
- Reception Dish: Receives the signal from the ground station.
- Satellite Broadcast: Sends the TV signal to a specific area of land.
- Transponders: A full range of electronic equipment for satellites (excluding antennas) responsible for receiving TV signals from a ground station via a radio frequency carrier within the microwave range.
To expand the number of channels that can be transmitted by each of these bands, polarization is used in the transmission of the signal, which can be:
- Linear Polarization: The shape of the electric field associated with the electromagnetic wave describes a linear path.
- Circular Polarization: The shape of the electric field associated with the electromagnetic wave describes a circular path by rotating on its axis. If the rotation is clockwise, the polarization is called right, and if counterclockwise, it is called left.
Zone of Satellite Coverage
The land area covered by the emissions from the satellite TV, with constant power flow density values, is fixed by the configuration of the satellite’s transmitting antenna. The first line around the center represents the boundary where the signal strength is half the power from the center of the coverage area. Another core value is the width of the beam, which depends on the size of the dish. The coverage area produced by the emission of the satellite antenna is called the main track. It is normal for satellites to have several tracks when needed to cover a land area of irregular shape.
Within the coverage maps, the following are referred to:
- Effective Isotropic Radiated Power (EIRP): Expressed in dB referred to 1W, its maximum value is at the center of the footprint or coverage area, decreasing as we move away from the center trace.
- Gain-to-Noise Temperature Ratio (G/T): Indicates the relationship between gain and noise temperature, expressed in dB per degree Kelvin.
Receiving Station for Satellite TV
The types of receiving stations are:
- Prime Focus Satellite Dish: The main element is located in the center of the parabola and concentrates the signal captured by the antenna.
- Offset Satellite Dish: The reflector is a section of a parabolic reflector surface, being much smaller than that of a prime focus parabolic reflector. The focus is shifted downward, so it is out of the surface of the antenna and yields a maximum of 70%.
- Flat Antenna: Built on small groups of elementary antennas fed with different settings to achieve optimum performance. These are connected so that individual signals are added for maximum performance, up to 80%. Its main advantage is the space occupied, making it suitable for embedded installations.
Feed: This is the element responsible for picking up any signal reflected by the dish and should be located at the focus of the parabola. The power supply consists of:
- Speaker: Receives all electromagnetic waves reflected from the parabola. They have various construction methods depending on the type of dish.
- Waveguide: This part of the feeder directs the electromagnetic waves to the probe. These waves are reflected on the interior walls, gathering in a zigzag motion and causing constant crossing between waves.
- Probe: This part of the feeder is housed in the waveguide, insulated by insulating material. It consists of a small electrical conductor, which acts as a dipole antenna due to the wave height with which it works.
Outdoor Unit: This comprises the part of the ground installations ready to be illuminated by the satellite radio broadcasts, with the exception of the dish and feeder. It consists of:
- Polarizer: This item is located between the feeder and the LNB. In the case of circular LNBs, it is part of the feeder. The types are:
- Linear Polarization Orthomode: Used when you want to have a single dish for the two linear polarities. It is used for collective TV reception facilities, allowing each user to have different TV channels. It has a single input signal and two outputs, one for vertical polarization and one for horizontal.
- Linear Polarization Discriminator: Not suitable for use in collective TV reception facilities because it can receive signals with different polarities and can have different channels of different polarity.
- Circular Polarization: Discrimination of the signals is made by a layer of insulating material, which determines the position of the circular polarization, discriminating between left and right.
- LNB (Low Noise Block Converter): This consists of an electronic circuit housed in a waterproof case. Its mission is to amplify and convert the high-frequency electric current from the probe, which transforms electromagnetic wave signals, to a lower frequency. Within the LNB, we find:
- Low-Noise Preamplifier: Amplifies the RF signal picked up by the wave, which has a very small value, incorporating a small noise level below 2dB.
- Local Oscillator: Converts the frequency captured by the antenna to values between 950 and 2150 MHz, called the intermediate frequency (IF). This is necessary and essential to distribute the signal via coaxial conductor to the indoor unit.
- Intermediate Frequency Amplifier: Amplifies the intermediate frequency obtained from the converter output, increasing the signal to values between 30 and 40 dB.
Indoor Unit: This is installed inside buildings and its mission is to process the intermediate frequency signals from the outdoor unit and provide a radio frequency signal in the UHF band to be applied to a TV as if it were a terrestrial TV channel. There are three systems for distribution: per-channel, F1, and F1 in VHF.
Internal and Collective Unity: The admission level is 60 and 20 dBm for TV signals and between 25 and 15 dBm for radio.