Editing Low-noise block downconverter (section)

==Low-noise block feedhorns (LNBFs) ==

With the launch of the first DTH broadcast satellite in Europe ([[Astra 1A]]) by [[SES (company)|SES]] in 1988, antenna design was simplified for the anticipated mass market. In particular, the [[feedhorn]] (which gathers the signal and directs it to the LNB) and the [[polarizer]] (which selects between differently polarized signals) were combined with the LNB itself into a single unit, called an LNB-feed or LNB-feedhorn (LNBF), or even an "Astra type" LNB. The prevalence of these combined units has meant that today the term LNB is commonly used to refer to all antenna units that provide the block-downconversion function, with or without a feedhorn.

[[Image:sky lnb.jpg|thumb|right|120px|LNBF for Sky Digital and Freesat in the UK]]
The Astra type LNBF that includes a feedhorn and polarizer is the most common variety, and this is fitted to a dish using a bracket that clamps a collar around the waveguide neck of the LNB between the feedhorn and the electronics package. The diameter of the LNB neck and collar is usually 40mm although other sizes are also produced. In the UK, the "minidish" sold for use with [[Sky (UK & Ireland)|Sky Digital]] and [[Freesat]] uses an LNBF with an integrated clip-in mount.

LNBs without a feedhorn built-in are usually provided with a (C120) flange around the input waveguide mouth which is bolted to a matching flange around the output of the feedhorn or polarizer unit.