Big Satellite TV Dishes
A big satellite TV dish generally uses a metallic reflector which forms a portion of a paraboloid of rotation. It transforms the spherical waves emitted by the radiating element, located in paraboloid focus, into plane waves, producing a radiation characteristic with a pronounced directivity along the axis of the paraboloid.
The narrow beam of electromagnetic waves received by the parabolic antenna is reflected and concentrated in the center.
Big satellite TV dishes have a very wide frequency band because the geometric features of the reflecting surfaces do not depend on frequency (reflector sizes are considered large in comparison with wavelength). The satellite antenna is connected to a radio transmitter device through a coaxial cable or a metallic waveguide in the form of an empty tube.
Huge amounts of Information are received on the Earths surface with the help of such satellite dishes, although in recent years smaller, more compact dishes have become more prevalent. These smaller dishes work on slightly different principles than do their larger counterparts.
Satellite Dish Diameters
The diameter of large satellite dishes varies depending on the characteristics of waves received or transmitted. Satellite television uses satellites located on elliptical orbits with a complete orbit time of about 12 hours or geostationary orbits, equipped with large parabolic antennas with diameters of between 9-12 meters, for a cleaner signal.
Satellite TV Frequencies
Satellite TV channel frequencies transmitted via satellite are received by a number of ground stations and distributed by transmitters and translators to cover a certain area or are received directly by individual viewers using home antennas. Ground stations use transmitters with output of about 5-10 kW, parabolic antennas of about 20-25 m and are equipped with the necessary equipment for tracking the location of satellites.Usually, the uplink and the downlink are set to different frequency bands (C or Ku), to avoid interference.
Using C-band satellites have about 24 channels of receive-issue with a bandwidth of 36-50 Mbits and Ku band satellites have up to 32 channels of reception-issue. To avoid interference, geostationary satellites should have a distance between them of 2 degrees or a degree, for those with C-band and Ku band respectively.