Satellite TV Reception: A Comprehensive Guide
Satellite TV Reception via Satellite
Satellites orbiting Earth at a distance of 35,806 km transmit signals in the 12.7-14.5 GHz frequency band (uplink) and receive signals in the 10.7-12.75 GHz band (downlink). The power radiated by a satellite is expressed as EIRP (Effective Isotropic Radiated Power) and is calculated as the product of the satellite’s transmission power (Ps) and antenna gain (Gs).
Satellite Components
Satellites capture electromagnetic waves at very high frequencies and consist of the following parts:
- Reflector: Receives the signal.
- External Drive: Collects the signal from the reflector and is located at the focus of the parabolic antenna.
- Reflector Support: Allows for the orientation of the satellite antenna.
Types of Satellite Dishes
Satellite dishes capture parallel GHz frequency waves and come in various types:
- Primary Focus: The outdoor unit is placed at the center of the parabolic dish. Waves hit the reflector and are focused on the focal point. This type offers 60% greater performance than the reflector diameter, typically 1.2 meters.
- Offset: A metallic arm extends below the reflector, with the outdoor unit placed at the end, coinciding with the parabola’s focus. This design avoids shadowing the reflector and achieves a yield of 70%, with diameters usually ranging from 0.6 to 1.1 meters.
- Cassegrain: Consists of two reflectors, a main one and a convex one located at the focus of the parabola. The outdoor unit is placed at the center of the main reflector. Waves hit the main reflector and are reflected onto the convex reflector, focusing on the outdoor unit. Diameters range from 2 to 30 meters.
Satellite Dish Orientation
Optimal signal reception depends on proper satellite dish orientation, involving two key angles:
- Azimuth: The angle provided to locate the satellite, either north or south.
- Elevation: The angle or slope formed by the reflector’s axis.
An inclinometer, a precision instrument, measures the elevation value and is placed above the reflector.
LNB (Low Noise Block)
The LNB amplifies and converts satellite signals. It operates with four possible voltage and tone combinations: 13V-13kHz, 18V-22kHz, 18V+22kHz, and 13V+22kHz. The LNB consists of two main parts:
- LNA (Low Noise Amplifier): Amplifies the signal and eliminates noise.
- LNC (Low Noise Converter): Converts the high-frequency satellite signal (9.75-10.65 GHz) to a lower intermediate frequency (950-2150 MHz) for transmission through coaxial cable.
Other Satellite TV Components
Several other devices play crucial roles in satellite TV reception:
- Converters: Change the frequency of a channel, improving signal quality and clarity.
- Modulators: Generate a modulated radio frequency (RF) signal from video and audio inputs, often used when indoor units lack built-in modulators.
- Mixers: Combine multiple input signals into a single output cable.
- Separators: Separate TV signals (channels or bands) present at the input and route them to different outputs.
- Filters: Select specific frequencies, with types including high-pass, low-pass, and band-pass filters.
- Attenuators: Reduce signal strength where necessary.
- Equalizers: Balance signal levels across different channels.
- Injectors: Power mast amplifiers or antenna preamplifiers.
- DiSEqC switch: Allows switching between multiple satellites (e.g., Astra and Hispasat) using a single coaxial cable.
- Multiswitch: Combines the functions of switches and allows multiple users to access various satellites and polarities.
Understanding these components and their functions is essential for setting up and maintaining a reliable satellite TV system.