An 'LNB', or 'Low-Noise Block', is a small component that is suspended over a satellite dish or minidish. A 'minidish' is the satellite dish supplied by satellite TV providers like Freesat and Sky Digital, for receiving satellite TV transmissions. The LNB receives the satellite signal, amplifies it, and sends it down through a cable to the set-top box inside a home or business. This makes the LNB a crucial part of the satellite dish system, and if it is not functioning properly the signal quality and therefore image quality is adversely affected.
An LNB is a small component. While it is not especially expensive component to buy, its importance to the proper functioning of the overall satellite dish setup, means that it must be chosen with care. Fitting the wrong LNB to the minidish can seriously degrade the operating effectiveness of the entire system, and this mistake can prevent the minidish from functioning at all. It is therefore important for the buyer to understand the basics of LNB, such that they can make an informed purchasing decision.
LNBs are made to different standards, and come in different formats, so it is important for the buyer to be able to select the appropriate LNB for his system at the right price. eBay offer buyers an extensive selection of LNBs, minidishes, and other satellite TV components at prices better than what can be found on the high street.
How Does the LNB Work?
The proper name for the LNB is a 'low-noise block downconverter,' which gives a strong hint to its main role. The primary function of the LNB is to receive and then amplify the microwave signal collected by the minidish, so that the signal can be sent via a cable or cables down into the house and to the set-top box connected to the television. This signal contains the digital information that, when decoded by the set top box, is converted into programming that is viewed on the television screen. Another part of the job of the LNB is to downconvert the signal to a lower frequency.
Low Noise Function
By the time the signal has been beamed across space from the satellite it is actually quite weak, which is why the LNB must amplify it in order to provide the set top box with a signal strong enough to use. The reason for the LNB being called a 'low-noise block' is that when amplifying the signal, it must do so in a way that does not create 'noise'. Noise in this case does not mean just sound, but any degradation of the purity of the digital signal. A quality LNB ensures that the amplification and transmission processes cause as little signal degradation as possible.
Maximising Signal Quality
Some LNB's use titanium and gold components in order to achieve the best transmission quality. This obviously affects the price of the LNB. Probably more important though, and certainly an essential part of choosing an LNB, is to match the LNB to the type and shape of the minidish.
Types of Minidishes
There are different types of minidishes. The minidish used by Sky Digital comes in two formats, depending on where in the United Kingdom the dish is being used.
Zone 1 Dishes
These minidishes are about 54 cm across, and are used in areas of the United Kingdom with good satellite signal reception.
Zone 2 Dishes
A zone 2 minidish is about 70 cm across, and are used for areas of the United Kingdom, such as Scotland where the satellite signal reception is weaker.
New vs. Older Format LNBs
To complicate matters further, the minidish has changed over the years, and there are therefore Type 1 LNBs, for minidishes that are more than a few years old, and a Type 2 LNB, for the latest in minidishes. The current Sky minidish, introduced in 2009, is the MK4. One can purchase an adaptor to fit the current, Type 2 LNBs to older minidishes. This 28 mm by 18.5mm adaptor enables the user to fit Type 2 LNBs to MK2 and MK3 dishes.
Sky minidishes use a non-standard fitting to attach the LNB, which means that many LNBs do not fit minidishes. Before buying an LNB, therefore, it is important to check that its fitting is compatible with the particular minidish it is intended for.
The Shape of the Dish
However, the availability of an adaptor does not mean that it is acceptable to buy just any LNB and fit it to a minidish. To ensure best performance from an LNB, it must be fitted to a dish of a particular shape. This is because each LNB is optimised to work with a particular shape of dish. This is referred to as the dish focus. The reason for this is that the minidish's ability to focus the signal it collects onto the LNB comes down to its shape. Off-focus LNBs are compatible with oval-shaped dishes, while prime focus LNBs are compatible with circular minidishes.For the same reason, it is essential that the LNB is installed at the exact focal point. Even one or two millimetres out will impair its performance. Both of the Sky minidishes mentioned above are oval in shape, therefore the LNB which is required is one designed for use with an oval dish.
Number of Output Cables on an LNB
An extremely important consideration when choosing an LNB to fit a minidish is the number of output cables. This can be either a single output cable, four output cables, or eight output cables.
The single output LNB has just one output cable. It is not a good idea to buy this unless the buyer is certain that their setup can function with just one cable, which many cannot. There is no two-cable LNB for the minidish, with the next size up being the Quad-LNB. This has four identical cables. Finally, there is the 'Octo', or Eight-Cable LNB. This feeds eight Digiboxes, but only four SkyPlus, HD, or Freesat boxes, as each box requires two cables.
The difference in price between the Quad-Cable LNB and Eight-Cable LNB is considerable, so it is worth checking exactly what the requirements are for the system.
Where to Buy an LNB
The question of price is always important. High street electronics stores that specialise in satellite TV setups, are not the venues where you are likely to find the best deals on satellite TV components. Nor are they always the best places to get advice, as busy sales staff often don't have the time to give proper help. Fortunately, LNBs are widely available on the Internet, where online retailers such as eBay have a good range of LNBs to choose from.
Finding an LNB on eBay
It is easy to find an LNB for a minidish on eBay. Begin your search by typing a simple search term into the search bar on the eBay homepage. For example, by entering 'satellite lnb' into the search bar, the local search engine populates results pages for listings for LNBs, as well as adaptors and other components, both new and used. You can filter these results further by specifying the characteristics you are looking for. If you want an LNB that is marketed under a particular brand, you can specify that results be sorted according to brand name. For example, you can specify that the search engine only show results for Inverto LNBs. If you want an LNB with eight output cables, you can make your selection under 'Number of Outputs' on the results page. You can also choose to only look at LNBs that are new or used. You can also sort listings based on compatibility: either off-focus (oval minidishes) and prime focus (circular minidishes).
When you have a set of listings that match your requirements, it is time to look through them to find the best LNB. Study the descriptions carefully. If you have any concerns related to compatibility with your existing minidish, you can contact the seller for advice by going into their profile page and clicking on the contact link. eBay Top-rated Seller are usually the ones most knowledgeable about the merchandise they offer for sale.
Although only small and not a very expensive component, an LNB, or low-noise block, is a crucial element of a satellite dish setup. Its function is to receive the satellite signal focussed onto it by the dish, amplify that signal, downconvert its frequency, and send it down the output wire or wires to the set top-box on the television. Unless the LNB is well matched to the shape of the satellite dish, and properly positioned at the focal point, the result could be poor picture and audio quality.
When selecting an LNB to fit a minidish, the buyer must consider the specifics of their existing satellite dish, including the type of dish, the shape of the dish, so as to determine compatible dish focus, and the number of outputs.
eBay offer buyers access to thousands of listings for satellite TV components, often at better prices than high street shops. Buyers also have access to knowledgeable sellers willing to offer advice about satellite TV setups.