Satellite dish owners, or those who simply want to know about satellite communications, may have heard the term "LNB." Low Noise Blocks (LNBs)--those small devices mounted to the front of satellite dish receivers--offer considerable functionality and great significance to the communication world. With several different types of devices and considerations unique to each, LNBs are interesting players in the world of satellite communications.
Definition
A Low Noise Block is the device mounted to the front of a satellite receiver ("dish") that receives the weak microwave signal incoming from a satellite, amplifies it, and converts it to a signal readable by consumer equipment designed for interpreting satellite communications.
Function
Satellite beams, constantly broadcast down from the sky, are caught by a concave receiver device (commonly known as a dish) and reflected onto a Low Noise Block. As the LNB receives these communications, which are typically broadcast at a frequency of between four and 21 gigahertz, it first applies a filter to remove any spurious microwave that might have been caught by the satellite dish. After unwanted signals are filtered, the LNB then amplifies the weak satellite signal, converts it to a lower frequency capable of traveling across coaxial cable, and sends the signal on to a special electronic decoding device connected to the satellite customer's television.
Significance
Because satellite communication signals are generally both very weak and extremely high in frequency, reception of these signals is dependent on devices capable of amplifying and interpreting the encoded message. By achieving this purpose, the LNB enables successful satellite communication for services such as global telecommunications, satellite television services, satellite Internet services, and even secret government transmissions. While myriad technologies are involved in creating and transmitting these communications, the LNB is responsible for the bulk of the work on the receiving end.
Types
Just as many different satellites are currently in orbit, many different communication types are constantly being beamed down from space. To interpret these different communication technologies, a variety of LNBs have been created. Arriving on Earth in either vertical or horizontal orientation, satellite communications fall into two different polarization types; these different polarizations require different LNBs to be effectively received. Dual-polarization LNBs, though, can receive both types of communication. Dual band LNBs, similarly, can receive multiple satellite communication frequencies. Finally, multi-LNBs (such as dual-LNBs, tri-LNBs, quad-LNBs) can send their output to more than one coaxial connection.
Considerations
Even with dual-frequency, dual-band, and multi-LNBs, misuse of LNBs or misdirection of the satellite dish receiver can overload Low Noise Block devices. Some larger satellite dishes, like those used in the late 1980s, can capture signals from multiple satellites, directing an overwhelming number of signals to the LNB. Likewise, LNBs designed to listen to very low-power satellites can be overloaded if the satellite dish is pointed toward a stronger, or higher powered, transmitter. When using an LNB and when positioning a satellite dish receiver, it is important to always follow the manufacturer's instructions and ensure the satellite dish is properly configured.
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