Satellite Dishes, Receivers and LNBs
Satellite dishes are a kind of parabolic antennas designed in such a way that they receive signals through microwave from circulating communication satellites. The communication satellites send out signals or broadcasts (satellite television) as well as data transmissions.
Due to their parabolic shape, the satellite dishes can reflect these signals to the center of the dishes. Typically the satellite dish is support on brackets at its center and the center or the focal point of the dish is called ‘feedhorn.’ The feedhorn is instrumental in gathering and conducting the signals to a low-noise ‘block down converter’ also known as Low Noise Block or LNB.
Low Noise Block or LNBs
What the LNB does is it converts the various signals emitted from radio or electromagnetic waves to a more readable electrical signal. It also has the capability to shift the signals received from various downlinked banks such as C and Ku to the L band. Most satellite dishes that are used for direct broadcasting have an LNBF that combines the capabilities of both the LNB with those of feedhorn.
Recently a new omni-directional satellite aerial that doesn’t require a parabolic dish is being used for moving platforms like a vehicle etc.
Physics of Satellite Dishes
As the frequency increases so does the directive gain. However, the factual gain is really dependent on many other factors that include the surface finish of the dish, the amount of accuracy employed to create the shape, and the feedhorn matching. The most commonly used commercial type satellite dishes having 60 cm diameter have a gain value of 37.50dB at 11.75 GHz.
Lower frequencies like C-band offer satellite dish designers’ flexibility with materials. Larger sized dishes are now being designed using metal mesh within a metal framework. The lower the frequency, the more versatility in materials and the better the performance. However, as the frequencies increase, metal meshes can’t be used.
Size of Satellite Dishes
The modern satellite dishes that are used for Direct Home TV come in standard diameter sizes between 43 cm (18 in) and 80 cm (31 in). These dishes are unidirectional to catch the Ku-band from other communication satellites in orbit.
The receiver is the end component in the Satellite TV system. The satellite receiver has 4 main jobs including descrambling an encrypted signal, converting digital formats like MPEG-2 or MPEG-4 signals into a format that a CTV can recognize such as analog, take out channel by channel from a bigger satellite and lastly, to send billing information and pay-per-view information of the customer back to the headquarters.
Satellite receivers have many other features too. From picking up programming schedule signals from the providers and send those to the customer’s TV in form of onscreen program guide to offer child-safe viewing etc. Satellite dishes, LNBs, and receivers all work in tandem to offer the end user an excellent digital viewing experience.
With sound and picture with a movie theatre like quality, today satellite TV is an excellent investment for all those who love to be couch potatoes.
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Satellite Cemetery - Dead Frequencies
Frequently Asked Questions...
A TV satellite dish is designed to receive waves of wavelength 3.9 meters What is the frequency of the waves?
A TV satellite dish is designed to receive waves of wavelength 3.9 meters What is the frequency of the waves it broadcasts?
Give you answer in MHz = 106 Hz.
Frequency(Hz)=Speed of light/Wavelength