The receiver controls LNB via coaxial-cable. Then the satellite signal reflected from the antenna is transmitted to satellite receiver and demodulate programs after first frequency conversion through LNB.
Each LNB has fixed local frequency. The local frequency of C-band is 5150MHz. At Ku-band, the local frequency is set according to different frequency band. At low band 10.7-11.7G, the local frequency is often9.75G; at 11.7-12.2GHz, it’s often10.75G, or 10.600,10.678G; At 12.2-12.75GHz, it’s often 12.25GHz or 11.3GHz. At present, most of the Ku-band programs choose this kind of local frequency.
Categories of Low Noise Block:
From receiving frequency, it can be divided into C-band and Ku-band Low Noise Block. The former one has large volume and the latter one has small volume.
From polarization mode, it can be divided into single polarization and double polarization Low Noise Block. Personal families often use double polarization Low Noise Block to receive; while cable project just needs single polarization.
From structure, double polarization Low Noise Block is integrated LNB, also called LNBF; while single polarization Low Noise Block is separated type, also called LNB, which should be matched with another feed. Now Low Noise Blocks are generally called LNB.
From local frequency, it can be also divided into single local oscillator and double local oscillator LNB.
The standard to measure the quality of LNB is noise factor. The higher the quality is, the smaller the matching antenna aperture is. For a C-band LNB, noise factor is showed with °K, and the value is the smaller the better. At present, some high-quality LNB has reduced the noise factor to 17°K.
The noise factor of Ku-band LNB is showed with dB, which is the smaller the better. The noise factor of a good Ku LNB should be 0.7dB. Also some are expressed with Gain. The gain of a good LNB should reach 65dB.
Categories of Ku-band LNB:
Because of the wide frequency range of Ku-band programs, the matching Ku LNB can be divided into Standard, Broad band Full band. The so-called broad band is a relative concept. As we all know, Ku-band signal is working at frequency11Gand12G, and this range can also be divided into 10.7-11.7G, 11.7-12.2G, 12.2-12.7G.. So we can say the LNB can just work in these frequency range is the so-called narrow-band LNB. Comparatively speaking, the frequency range like 11.7-12.7Gcan be called broad band. And that LNB to receive frequency range like 10.7-12.7Gcan be called full band. So far, the Ku-band satellite television programs over Asian-pacific region have a lot of11Gsignal except the normal12Gsignal programs.
The frequency range of broad band LNB is 11.7-12.7G, and the common local frequency is10.75G.
The standard LNB refers to LNB with 11.25 or11.30Glocal frequency, and receiving 12.2-12Gsignal.
The full band LNB refers to LNB which receives all the signal in range 10.7-12.7G. All these LNB are double local oscillator. Low local oscillator is9.75G, which is to receive signal in frequency 10.7-11.7G. High local oscillator is generally10.75G, also 10.6,10.678Getc. which is to receive signal in 11.7-12.7G..This kind of LNB is controlled by the 0/22KHz switch in digital machine. When the switch is off, LNB works on low local oscillator; while it’s on, it works on high local oscillator.