Low-noise block converter

Satellite signals are transmitted through comparatively high radio frequencies. LNB is the waveguide based receiving  antenna of the parabolic satellite dish, functionally equivalent to the dipole antenna used for most TV reception purposes. The dipole antenna must be rotated to adopt the various polarization planes, whilst the LNB, usually fixed at the satellite dish, allows electronic switching between vertical and horizontal polarization. The corresponding component in the uplink transmit link is called a Block upconverter (BUC).

LNBF disassembled
Since the microwave satellite signals can not pass easily through such barriers as walls, roof, or even window glass, it is necessary to place satellite antennas outdoor, then passing the signal indoors through the coaxial cable. When radio signal is sent via cable, with increasing frequency losses increase as well. Such high frequency of the signal would require cable of special type, which is quite expensive, and the cable of significant length leaves very little signal level on the receiver.
LNB is designed to use the superheterodyne principle taking a wide band of high frequencies, amplifying them and converting to similar signals of much lower frequency which is called intermediate frequency(IF). Such lower frequencies pass through the cables with much less signal attenuation, hence much more signal proceeds to the satellite receiver. By operating with these lower frequencies it is much easier and cheaper to design electronic circuits.
The low-noise means using special electronic engineering techniques for the amplification and mixing before cable attenuation, and that the additional electronics like a digital receiver or a power supply are not connected to the block. Thus the signal with lower noise (unwanted signals) on the output is achieved. Simply speaking, the higher the electronic component operational frequencies, the more critical is issue of noise to be controlled. The quality of picture and sound of satellite TV would be very low, if low-noise engineering techniques are not used. Signal, possibly, could even be received not at all requiring a much larger satellite dish. The low-noise LNB feature is displayed as the noise figure.

LNBFs

linear-polarized Ku-band LNBF
Direct broadcast satellite (DBS) dishes operate with LNBF (LNB with feedhorn), which represents the low noise block converter (LNB) integrated with antenna feedhorn. To distribute the resulting IF signal (usually 950 to 1450 MHz), are used the small diplexers combined with the same coaxial cable jacket which carries lower-frequency television from an outdoor antenna. Another diplexer then separates the signals to the TV set receiver, and the DBS set-top box integrated receiver/decoder (IRD).

Newer Ku band systems use additional IF blocks, one of which cause interference to UHF and cable TV frequencies above 250 MHz, precluding the use of diplexers. The other block frequencies are higher than the original, up to 2.5 GHz, which makes it necessary for the LNB to be connected with all-copper RG-6/Ucables of high-quality, in addition to higher electrical power requirements for multiple dual-band LNBFs.
For some satellite Internet and free-to-air (FTA) signals, a universal LNB (Ku band), such us our Prof LNB (Ku band), is recommended. Instead of linear polarization, vost North American DBS signals use circular polarization,  thus different LNB type for proper reception is required. In this case, the polarization must be tuned clockwise and counterclockwise, rather than horizontal and vertical.
With DBS, the voltage supplied to the LNB determines the polarization setting. In multi-TV systems, a dual LNB allows both polarization to be selected by a switch acting as a distribution amplifier. Then the proper signal proceeds to each box pursuant to what voltage has been selected. Instead this, the newest systems are sending DiSEqC codes to select polarization and LNBF to use.

Universal LNB
A universal LNB receives both Vertical and Horizontal polarisations with the full frequency range in the satellite Ku band. Some models of LNB converters (referred to as quattro LNB used with a multiswitch)  simultaneously receive both polarisations via four different connectors.

North American Standard Ku-band LNB
LNB with a better noise figure produced by covering a smaller frequency range.

Dual/Quad/Octo LNBs
The unit consisting of two, four or eight LNBs allowing to use multiple receivers on one dish. {Note that in the UK such a term as "dual" is reserved for LNBs with two feedhorns, like Monobloc type(see below), whilst the "twin-output" term is used for LNBs with two separate outputs.}

Quattro LNB
A special LNB type called quattro LNB is used to provide a shared installation for signals delivery to any number of receivers through one or more multiswitches. This converter features four outputs that can’t be connected directly to receivers. Each of these four outputs supplies only the quarter of channels available (Lo/Hi band and H/V polarization) to a multiswitch or a set of multiswitches, which then supply individual receivers in the same way as it would have been made by the normal LNB output.
Again, there is the difference between a quattro and a quad (also double twin). LNB of quad typeis capable to drive four receivers directly. LNB of a quattro type, in its turn, has four separate outputs, each of which is equipped with an independent band/polarization switch.

LNB Monoblocks
Designed to receive signals from satellites that are spaced close together, generally 6°, a Monoblock LNB ("monobloc" as well) is a unit consisting of two LNBs. For example, in some parts of Europe, popular are the monoblocks for the Hot Bird and Astra 19.2°E satellites reception because they allow to receive both satellites with a single dish without noisy and expensive rotator. Duo LNB provides a similar advantage simultaneously receiving both the Astra 23.5°E and Astra 19.2°E signals.