LNB is an acronym for Low Noise Block. It is a technology used in reception from satellite communications. It is also referred to as LNC-Low Noise Converter. An LNB is affixed on a satellite dish. As it were, signals used for satellites are high frequency that require special cable types or waveguides. If the cables become longer, this leaves very little signal for the receiving end. This is where the LNB comes in. By utilizing superheterodyne effect, LNB amplifies signals within 10.95-12.5 GHz using single low-noise, wide-band amplifiers, and converts the signals to much lower frequencies that are called Intermediate Frequency or IF. The low frequency signals travel with much less attenuation of the signal and therefore, more signal is left on the receiver end of the cable. This makes up for the signal loss with coaxial cables with a 0.66 % velocity factor depending on how high the frequencies are.
“Low noise” refers to the quality of the first stage input amplifier transistor which is measured in units known as Noise figure, noise temperature and noise factor. Noise factor and noise figure can be converted into noise temperature. Low noise temperature is better. Thus, an LNB with a low temperature of say 100k, would be better than that with a 200k temperature. The “Block” part is a reference to a bundle, or block of microwave frequencies that are received from the satellite having been converted to a lower block of frequencies in the cable to the receiver. That would probably be an over simplification of LNB. More complex LNBs exist especially for satellite TV receivers, whereby people might want to receive signals from different bands simultaneously and with alternative polarizations.
The essence of LNB is to control the noise temperature before signal processing. LNB helps maintain the quality of the sound and picture from satellite televisions without necessarily using a satellite dish with a larger diameter. There are three types of LNBs that are used for domestic applications. The first one incorporates a 10 GHz local oscillator which worked with contemporary receivers to enable reception of SHF frequencies. This technology was used before the advent of the Astra ID satellite and other satellites in the Eutelsat group. The aforementioned satellites brought about an enhanced system in which the LNB’s internal oscillator runs at 9.75 GHz to receive the inbound frequencies between 10.7 to 11.7GHz. Nowadays, it is the third type (christened the “universal type”) that is mostly used. It is a wideband type of LNB, and this means it is capable of receiving the entire 2.05GHz frequency spectrum that is used for TV and other uses in Ku band.
LNB Faults.
Sometimes, black and white dashes overlay the pictures being transmitted in an analog satellite television. It affects the highly-colored areas in PAL encoded images. The commonest cause for this is the low carrier-to-noise ratio of the received f.m. video signal. This usually occurs after a heavy downpour. Or it might sometimes come about due to incorrect positioning of the dish to face the satellite. Qualified technicians should be able to fix the problem by making sure there is no ingression of water, or if the problem is inaccurate positioning, the technicians will correctly position it.
Additional Reading on LNB’s
