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Technical Index Aerial+LNB 1 Cable Aerial amplifier Aerial Filters Aerial Groups Aerial Points Aerial - Which? Amp Adder Analogue Switch-Off A18QR aerial Arcon Dish Atticbox Audio Adapter USB AV equipment BBC/ITV outside UK Bedroom sound Best aerial Cable Kinked Cable specs Cable-Thin Coax Cable - Which? CAMs etc. Capacitor Kits Channels Chimney Brackets Coaxial Cable Cooling fan Compass use Cupboard Control DAT45 aerial DC inserter Decouple cable Denso Tape Digibox in loft Digisender Digital Ariel Diplexers DirecTV Disconnect safely Disguise a dish Dish indoors Dish Painting Dish Sharing Dish Size E-books Electric shocks Electronic Kits Electronic Parts Epoxy resin glue Extend cable Extender Plate F1 for Free Filter-notch Fire Hazard Fit F Connectors Fit TV plugs Foxsat HDR Free channels Freeview/Freesat Freeview Problem Freesat Install DIY French sat TV German sat TV Greek sat TV Heatshrink Sleeving Hole Cover Humax PSU Inside Sky Digibox Instructions Interference Invacom LNB Italian sat TV IR sensor-locate Large Dishes Lightning Protect Liquid Spilt LNBs - about LNBs - add more LNB amplifier LNB Boots LNB Fitting LNB-Replace Sky LNB Reset LNB skew LNBs-Switching two LNBs 2 in 1 cable LNB-waterproof your Loft Boxes Magic eyes Make Fly-Lead Multiroom phone Multiswitches No Satellite Signal Omnisat Semitronic Orbital dish Phone Socket Wires Phone surge protect Plate-Twin-F Plugs-which? Plug-Top PSUs Plus Combiner Powermid+cable TV Powermid XL Reed Switches Remote Codes Remote Eyes Remote extenders RJ45 plugs Satellites-where Scart leads Self-Amalg Tape SelfSat Antenna Signal Combiners Signal Meter Silicone Grease Sky x2 same room Sky+ batteries Sky Digital Sky in Europe Sky Install DIY Sky LNB Sky LNB-extra Sky Multiroom Sky Remote Probs Sky room wiring Sky Plus Solder - How to Split Digibox RF Split Dish cable Split satellite signal Stacker-Destacker Stuck in standby Thomson Problems Tree blocks signal Triax minidish TV/VCR faults TV Links tvLINKplus TV set New TV eyes USALS Videosenders VisionLink Wall Plates WF125 Plugs What Channels Which plugs Wire my house 304114 wall plate Shop Index All Aerials Aerial Amplifiers Aerial Attenuators Aerial Boosters Aerial Filters Aerial Hardware Aerial Meters Aerial Splitters Audiophile Bargains Books to download Boosters, Amps Cable & Extensions Cable Joint Cable on Reels Capacitors Caravan/motorhome Car Radio Adapters CAT5-HDMI Components Computer Batteries Computer Leads Digibox spares DiSEqC Switches Dishes Dish Hardware DVD Players Earth rod Electrical - mains Electronic components Electronic Kits Electronic Kits 2 Extension - Coax Extension - mains Faceplates Filters electrical F Plugs Fly Leads Freeview cable Freesat Digiboxes FTA Digiboxes Freeview receivers Fuses Gaming Accessories German Sat TV HDMI / Audio Headphone Amp Home Cinema Installation kits Leads + Plugs LED Torches LNB cable LNBs for Sky LNBs 40mm LNBs C120 LNB switches LNB amplifiers Loft Boxes Magic Eyes Mains Electrical Meters Motorhome Motorised dish bits Multiswitches Power supplies Remote Controls Remote extenders Resistors RF Cable RF Modulators Satellite Cable Satellite Meters Scart Leads Screen Cleaning Signal Combiner Sky Digiboxes SkyLink Amplifiers SkyLink Bypass Splitters Telephone cable Thomson PSU Tools Grease Glue Transistors TV Eyes TV Plugs TV Wall Brackets Videosenders Video/Leads Wall plates 1 Wall plates 2 Technical Index FAQs BLOG Contact Us		Satellite dish LNB help   LNB mysteries explained - Part 1 Send this page address - CLICK HERE - to a friend ! If you've read part 1, you might like to read Part 2. All our LNBs are "universal" type so they work with ALL modern digital satellite TV receivers. What's the Best LNB? How to test an LNB? Oval or round? What LNB do I need for HD/SD? What LNB do I need for DiSEqC? Can I split the feed from one LNB to two tuners? Universal LNB Twin-output LNB Dual or Monobloc LNB Quad-output LNB OCTO 8-output LNB Quattro LNB What is an LNB? Low Noise Block-downconverter (so called because it converts a whole band or "block" of frequencies to a lower band). Also incorrectly known as a "Low Noise Block" or a "Low Noise Blocker"! An LNB sits on the end of an arm and faces the parabolic reflector ("dish") which focusses the signals from a satellite 24,000 miles away into the "feed horn" of the LNB (see pictures below). The LNB converts the signals to a lower frequency and sends them out to the cable connector, which you connect to your satellite receiver via coaxial cable. What is an LNBF? This is the term for an LNB with an integral feed horn. Nowadays the "F" tends to be omitted. What is an LNC? Low Noise Converter. Basically the same thing. A modern "universal" LNB is able to operate in four modes to provide signals from four frequency bands, known as "low-horizontal", "high-horizontal", "low-vertical" and "high-vertical". An LNB may have more than one output but any one output can provide only ONE of these bands at a time. In order to tell the LNB output which of the four frequency bands it needs to provide, the receiver "communicates" with the LNB as follows (this gets technical):- A modern "Universal" LNB requires a 22 kHz signal at 0.5v p-p to switch its Local Oscillator to 10.6 GHz ("high band"). Otherwise it uses its 9.75 GHz oscillator. Polarisation switching is controlled by DC voltage supplied by the receiver. 12.5v to 14.5v gives vertical and 15.5 to 18v gives horizontal polarisation. A higher voltage than that can damage the LNB. A voltage that is too low will prevent the LNB from working correctly. Under normal circumstances, one cable can carry only one LNB feed (because of the voltage and tone communication method), although it is sometimes possible to use a "stacker-destacker" to carry two. How does an LNB work? Click HERE. ============================ What's the Best LNB? We try to stock the "best" available. For example, the "Invacom quad" has the best cross-modulation performance of all the LNBs I've had tested. In layman's terms, this means that a weak transmission on one polarisation is less likely to be drowned out by an adjacent strong signal on the opposite polarisation. This parameter will be of interest ONLY for a dish of 2m diameter or larger. On an 80 cm dish you might as well use the cheapest LNB you can find because it won't be able to collect a strong enough signal to cause this cross-modulation problem. As another example, the (obsolete) Thomson Sky LNB was said to have a higher gain than usual. (This is hearsay - I never had it measured). The result was (allegedly) that it could be used with a longer length of cable BUT, some receiver tuners got overloaded if it was used with a short length of cable. So you might say that this LNB would "perform better" with a long cable run (but it might be crap with a short length). An important point to recognise is that an LNB will work at its best when it matches the dish. This means that an LNB which is designed to focus on a dish which is circular (when viewed from the LNB position) will not give its best if you fit it to a dish that is wider than its height - and vice-versa. In addition, the LNB must be fitted so that it sits at the exact focal point. A couple of millimetres either way will reduce the amount of signal and increase the amount of interference. The LNB "skew" (rotational position) must also be correct, otherwise signals of opposing polarisation will interfere with each other. Assuming that you've chosen the correct type of LNB and got the adjustments right, it's unlikely that you'll benefit from changing it for a different make of LNB. You'll see all sorts of silly claims such as "0.2 dB noise figure". Believe me when I tell you that any noise figure below 0.9 dB is fine. You won't see any difference whatsoever - even if the claimed noise figure is correct. Dish size is what matters, and dish quality. There are some dishes on sale which are flimsy and poorly made. We don't stock these. If you buy on price alone, be prepared for disappointment and bear in mind that it's much easier to swap an LNB than a dish. If you swap an LNB and see an improvement, it's likely that the first LNB was OK but was designed for another dish and probably didn't have the range of adjustment required to set it at the exact focal point. However, LNBs can and do fail so don't discount the LNB when you look for fault causes. Note: we stock LNBs for Sky dishes and LNBs for "circular" dishes. Do not mix the two. As far as we can tell, the LNBs that we supply match their respective dishes adequately, so there's no point asking us about this before purchase. However, if you find a problem after purchase, we do want to hear about it. How to test an LNB? I think my LNB is faulty. How can I test it? The only way to fully test an LNB is to fit it to a suitably aligned dish and connect a satellite receiver. Then check to make sure every channel is there. If no channels are missing and if it continues to work through a hot day and a cold night, the LNB is fine. However, if some channels still appear to be missing (with a known good LNB), this could be the fault of the cable (bad connection, water ingress or kinked or wrong type), the receiver or the dish (distorted or misaligned) or local interference (DECT phone, car radar detector, etc.). So then you need to use a process of elimination by swapping the dish, the cable and the receiver (for a different make/model as some receivers won't work correctly with some LNBs). Note that some wall-plate connectors can also cause "channels missing" problems and some electronic devices (DECT 'phone base stations, "Snooper" type radar detectors and microwave ovens) can cause similar problems. I've even had it reported that a bad battery connection in a laptop computer wiped out some channels! Can't I test it with a meter? You can NOT test an LNB with a multimeter. A cheap Satfinder meter is more useful but it simply looks at the average strength of all frequencies. It will not tell you if some frequencies are missing. An expensive meter looks at a specific frequency (sometimes more than one) but it will not tell you if some frequencies are missing. Also, most meters rely on battery power. If the battery can not supply enough current to the LNB, it may give a false reading. In short, you can not fully test an LNB with any meter but you can perform a partial test. Could I have damaged my LNB? A "universal" LNB is designed to operate normally with an input voltage of up to 20 volts. At a somewhat higher voltage, you can expect the LNB to fail. The time taken to fail depends on the applied voltage and duration. It would take a highly unusual fault to cause a Digibox to provide more than 20 volts and any digibox that did so would almost certainly emit expensive smoke within seconds. What LNB do I need for HD/SD? All modern receivers use a "universal" LNB which is compatible with all signals. Make sure that the LNB you choose has sufficient outputs for your receiver(s) which will have one or two inputs each. You can not "split" the LNB cable because each receiver input controls its own LNB output exclusively. What LNB do I need for DiSEqC? DiSEqC is a signalling protocol used by some receivers (not Sky) to control an LNB switch or a dish positioner. It is also used by some LNBs which have a built-in DiSEqC switch. This type of LNB is called a "Monobloc" or "Dual-horn" LNB. Can I split the feed from one LNB to two tuners? Yes but it won't work properly. You should fit an LNB with more outputs. Please click HERE for a full explanation. Which cable goes where? In theory, all LNB outputs are equal so it doesn't matter which you use. Protect unused outputs with a lump of "Blu-Tack" or other weatherproof seal. In practice, we've had reports that the centre two outputs of an Invacom quad-output LNB produce a slightly better signal than the outer two when fitted to a large dish of 1.8m diameter or greater. We have not tested this theory and it applies only as stated; it does not apply to any other LNB or to a smaller dish size. If you use a Quattro LNB then the order of connection to a multiswitch does matter! List of Universal LNB types:  The term "universal" is used to describe an LNB that has "dual band" tuning capability. It came after the "enhanced" LNB which had a slightly extended tuning range and used a 9.75 GHz oscillator instead of 10.0 GHz. Some people mistakenly think that "universal" refers to "universal fitting", meaning the LNB will fit any dish. There is no such LNB. It's important to choose an LNB which is suitable for your dish and matches your receiver. (All modern "digital" receivers in the UK will work with a "universal" LNB. The same is NOT true for the USA.) A Universal LNB requires a 22 kHz signal at 0.5v p-p to switch its Local Oscillator to 10.6 GHz ("high band"). Otherwise it uses its 9.75 GHz oscillator ("low band"). Used by ALL modern satellite receivers for Sky, Freesat, FTV and FTA viewing. Polarisation switching is controlled by dc voltage supplied by the receiver. 12.5v to 14.5v gives vertical and 15.0 to 18v gives horizontal polarisation. A higher voltage than that may damage the LNB but most are OK up to 20v. A voltage that is too low (less than 12.5v) will prevent the LNB from working correctly. Single-Output universal LNBs Note: single-output LNBs are seldom used nowadays unless you have a specific reason - such as squeezing several LNBs together on one dish. Most people keep their options open by fitting at least a quad-output LNB, which provides four separate feeds for (say) four satellite TV receivers or two Sky+ or HD PVRs. (You can't split an LNB feed so be sure to install an LNB with as many outputs as you are likely to need in the future.) Typical single-output "Universal" LNB 9.75 and 10.60 GHz L.O. The (obsolete) Cambridge "Platinum" Geo Universal G57" LNB Works in 2 bands* 10.7-11.8 and 11.6 - 12.7 GHz. (22 kHz signal switched). Noise Figure usually 1.0 dB or better. Integral feed horn with 40 mm neck but C120 flange type available in some models. Spigot fitting for Sky Minidishes. "Twin-output" universal LNB Previously available in Standard (10.0 GHz) and Enhanced (9.75 GHz) form, but now only in "Universal" form (9.75 + 10.6 GHz), the twin-output LNB provides two outputs to feed two separate receivers for independent working. Each output can be switched independently by 13/17 volt input by the individual receiver to change polarisation and by 22 kHz to change the band. This type of LNB is sometimes offered with an adapter to fit it to an oval Sky minidish. Beware! It is not designed to focus on an oval dish so its performance when the signal is compromised by bad weather will not be optimal. "Duo LNB" or "Monobloc LNB" Comprises two universal LNBs fixed together at a small angle in a single housing. Only one "F" connector is used. A single coaxial cable connects to the Digital (or Digital + Analogue) receiver which must be able to use DiSEqC signalling to select which LNB is to be used. A "Monobloc" (or "Monoblock") is normally used on an 80 cm dish to receive Astra at 19.2'E and Hotbird at 13'E (but not simultaneously). A double LNB called a "Duo LNB" will usually be for reception of Astra 23.5°E and Astra 19.2°E. Monobloc set-up Monobloc setting up This type of LNB has a single output and the actual satellite signal is selected by the receiver which sends a DiSEqC (22 kHz) pulsed tone up the LNB cable. So only one satellite transmission can be viewed at a time. This is in contrast with dish systems that have two or more separate LNBs where, with two receivers, both satellite transmissions can be viewed or recorded simultaneously. See picture HERE. Not compatible with a Sky Digibox. Not usually suitable for fitting to a Sky minidish (although it can be done - but expect poor performance in bad weather). "Quad-output" or "Quad universal" LNB This universal LNB can feed four separate receivers. Each receiver has independent control of polarisation and band via 13/17v switching and 22 kHz o/off respectively. This LNB is used with the new Sky Digiboxes and Freesat receivers that have two LNB inputs and internal Hard Drives for recording a programme while you watch another. Two LNB outputs go to this "Sky Plus" Digibox (or Freesat+) and the other two LNB outputs can go either to two standard Digiboxes or to one other "Sky Plus" (or Freesat+) Digibox. As illustrated, this LNB is not suitable for use with a Sky minidish. The Sky minidish version has a spigot fixing. "OCTO" universal LNB As above but with eight independent outputs. We stock a Sky minidish "spigot" version and a standard (40 mm neck) version. The latter works well with a 60 cm dish in the UK. "Quattro" universal LNB This has four fixed outputs and is used only in "head end" I.F. distribution systems (or "multiswitch") for apartment blocks. One LNB supplies a head end unit that can provide (typically) up to 16 outputs for separate Digiboxes. The four outputs of the LNB are as follows:- 1. Horizontal polarisation low band 2. Horizontal polarisation high band 3. Vertical polarisation low band 4. Vertical polarisation high band You should not connect any of the Quattro outputs, 1 - 4, directly to a receiver (except for testing purposes) unless you want to restrict viewing to just one of the four band options. Even if you do, the receiver may not work. If you simply need four or eight outputs, use the Quad or OCTO instead. No Quattro is manufactured to fit a Sky minidish. It always requires a (roughly) circular dish. Click HERE to see a suitable dish for England. How do I get more than 8 LNB outputs? Connect a QUATTRO LNB to a MULTISWITCH If you "mix 'n' match" by picking a 60 cm 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 LNB). There are some exceptions: a dish optimised to hold more than one LNB may be an "odd" shape. Some dishes are oddly shaped for mainly aesthetic purposes. However, a dish which is considerably wider than it is tall (as viewed by the LNB) will need a special LNB for optimum performance. Just to prove the point, here is a very early type of "Universal" LNB used with a Sky "minidish" (no longer manufactured). The minidish is oval in shape, being much wider than it is high. Inside that plastic rain cover is the actual LNB. Note the difference in scalar ring height (red arrows). The side projections allow the LNB to focus on a wide area in the horizontal plane, while the top and bottom projections are longer and focus the LNB on a narrower area in the vertical plane. This LNB is designed specifically for an oval dish and will give very poor results with a dish that is roughly circular or a dish that is taller than it is wide. Here's another comparison. The SX1019 on the left has circular scalar rings inside the feed horn. It is designed to be used with a nearly circular dish. The SX1019/S on the right is designed specifically for a Sky minidish which is wider than its height. This type of LNB can also be used with a Raven dish of a similar shape to the Sky minidish. Both LNBs are made by Philips. The one on the right, however, is branded "Skyware". Sky "Minidish" upgrades Here is an obsolete Philips SC519QS/S Quad output LNB, which used to be supplied with the SKY-plus system with adapters for the "minidish". The red arrow points to the special oval shaped "scalar" steps in the feed horn. These cause the LNB to focus exactly on the oval shape of the "minidish", using the full dish area but without picking up reflections from the wall behind. This type of LNB would not give good results with a circular dish. Some dealers are offering a standard Twin-output or Quad output LNB with an adapter to fit the "minidish". The adapter fits a treat. Unfortunately, the LNB will not give optimum performance - and could give "rain dropout" during bad weather. (We can supply an adapter to fit a 40 mm LNB to a Sky minidish but you use it at your own risk). However, you may prefer to buy a standard dish of, say, 60 cm diameter and use a standard 40 mm neck twin-output or quad-output LNB with this. The match and fitting will be perfect and the "rain dropout" will be very rare. If you are fitting a Quad-output or OCTO LNB to your dish, read this page. The LNB, above, has a spigot which fits into the Sky minidish arm. The LNB rotational position or "skew" can be adjusted by slackening the two screws that secure the spigot and twisting the LNB until best signal quality is achieved. The LNB on the left has a single screw but the principle is the same. A Sky LNB will often have graduated marks from 1 to 5 as a guide to alignment. Start at 3 and twist each way to locate the best position. More information in our eBook, below. More about LNBs - in Part 2. Send this page address - CLICK HERE - to a friend ! Copyright ©1998-2011 Martin Pickering Version 1.9 updated on July 22, 2011