page_title: Low-noise block downconverter
section_title: Universal LNB ("Astra" LNB)
hierarchical_section_title: Low-noise block downconverter / Common LNBs / Ku-band LNB / Universal LNB ("Astra" LNB)
caption_attribution_description: English: LNB for the Astra satellite TV system
context_page_description: A low-noise block downconverter is the receiving device mounted on satellite dishes used for satellite TV reception, which collects the radio waves from the dish and converts them to a signal which is sent through a cable to the receiver inside the building. Also called a low-noise block, low-noise converter, or even low-noise downconverter, the device is sometimes inaccurately called a low-noise amplifier.
  The LNB is a combination of low-noise amplifier, frequency mixer, local oscillator and intermediate frequency amplifier. It serves as the RF front end of the satellite receiver, receiving the microwave signal from the satellite collected by the dish, amplifying it, and downconverting the block of frequencies to a lower block of intermediate frequencies. This downconversion allows the signal to be carried to the indoor satellite TV receiver using relatively cheap coaxial cable; if the signal remained at its original microwave frequency it would require an expensive and impractical waveguide line.
  The LNB is usually a small box suspended on one or more short booms, or feed arms, in front of the dish reflector, at its focus.
context_section_description: In Europe, as SES launched more Astra satellites to the 19.2°E orbital position in the 1990s, the range of downlink frequencies used in the FSS band (10.70–11.70 GHz) grew beyond that catered for by the standard LNBs and receivers of the time. Reception of signals from Astra 1D required an extension of receivers' IF tuning range from 950–1,950 MHz to 950–2,150 MHz and a change of LNBs' local oscillator frequency from the usual 10 GHz to 9.75 GHz (so-called "Enhanced" LNBs).
  The launch of Astra 1E and subsequent satellites saw the first use by Astra of the BSS band of frequencies (11.70–12.75 GHz) for new digital services and required the introduction of an LNB that would receive the whole frequency range 10.70–12.75 GHz, the "Universal" LNB.
  A Universal LNB has a switchable local oscillator frequency of 9.75/10.60 GHz to provide two modes of operation: low band reception (10.70–11.70 GHz) and high band reception (11.70–12.75 GHz). The local oscillator frequency is switched in response to a 22 kHz signal superimposed on the supply voltage from the connected receiver. Along with the supply voltage level used to switch between polarizations, this enables a Universal LNB to receive both polarizations (Vertical and Horizontal) and the full range of frequencies in the satellite Kᵤ band under the control of the receiver, in four sub-bands:
  Here is an example of a Universal LNB used in Europe:
  Noise figure: 0.2 dB typical
  Polarization: Linear
caption: Astra type LNBF
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