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Message: <blockquote data-quote="T24" data-source="post: 41760" data-attributes="member: 175385">LNBLow Noise Block-downconvertor (so called because it converts a whole band or "block" of frequencies to a lower band). ============================Is there actually a different LNB for prime focus dishes + offset dishes? Surely an LNB's innards are the same and the feedhorn or the C120 flange is the only difference?In the old days, LNB noise figures were high, the gain (amplification) was low and satellite transponder power was typically 20 Watts. Imagine trying to see a 20 Watt light bulb 24,000 miles away! (You'd have trouble seeing a 20W bulb at the end of a 24 yard corridor).So, an LNB and feedhorn had to be matched to the dish. The internal antenna of the LNB had to be at the exact focal point of the dish and the horn had to be flared in such a way that, with the LNB at the focal point, the horn could "see" the exact circular area of the dish - no more and no less. If it was less then it wasn't collecting signal from the full area of the dish. If it was more, it was also collecting unwanted "noise" from any warm object (wall) or from the sky behind the dish.A good compromise was to take just part of a much larger paraboloid dish and mount the LNB in an "offset" position. The curvature of this partial dish is such that the focal point is now much lower so the LNB and feedhorn no longer obscure the signal path as they would with a "prime focus" dish.Nowadays, satellite transponders can produce typically 50 or 60 Watts and LNBs have higher gain and lower noise figures. With these strong transmissions, you can get away with murder. People stick any old thing on the end of the boom arm - which rather explains why one man's 0.6dB LNB is another man's nightmare when the signal strength is not optimum! The Sky minidish, for example, is a compromise between size and performance. It's very important that the LNB matches the dish exactly. This is one good reason why the dish comes with its own LNB.The manufacturers might "fudge" the issue if asked. After all, if they admit that their LNB works best with, say, an 80cm Lenson Heath dish and you just bought an 1 metre dish made by someone else, you might not be too happy.If you "mix 'n' match" by picking a 60cm dish and a Universal LNB at random, the chances are that the performance could be no better than that of the Sky minidish.As a general rule, any standard LNB will work with a circular (prime focus) dish or an offset focus dish which is taller than it is wide (which "looks" circular when viewed by the LN<img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite6" alt=":cool:" title="Cool    :cool:" loading="lazy" data-shortname=":cool:" />.However, a dish which is wider than it is tall will need a special LNB..........................................................................................................Types of LNB<ul> <li data-xf-list-type="ul">Universal</li> <li data-xf-list-type="ul">Twin</li> <li data-xf-list-type="ul">Dual</li> <li data-xf-list-type="ul">Monobloc</li> <li data-xf-list-type="ul">Octo</li> <li data-xf-list-type="ul">Quad</li> <li data-xf-list-type="ul">quattro</li> <li data-xf-list-type="ul">C Band</li> <li data-xf-list-type="ul">Unicable</li> <li data-xf-list-type="ul">Ka Band</li> <li data-xf-list-type="ul">Ku Band</li> <li data-xf-list-type="ul">C120</li> <li data-xf-list-type="ul">WR75</li> </ul></blockquote>

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