If you've read part 1, you might like to read Part 2. Oval or round?
Can I split the feed from one LNB to two tuners?
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.
How does an LNB work? Click HERE.
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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, the receiver or the dish (distorted or misaligned). 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.
Can't I test it with a meter?
A cheap satfinder meter 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.
List of Universal LNB types:
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| 3) "Universal" LNB 9.75 and 10.60 GHz L.O. The 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 40mm neck but C120 flange type available in some models. Spigot fitting for Sky Minidishes. A Universal LNB requires a 22kHz signal at 0.5v p-p to switch its Local Oscillator to 10.6GHz ("high band"). Otherwise it uses its 9.75GHz oscillator ("low band").
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 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.
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.
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| "Twin-output" LNB
Previously available in Standard (10.0GHz) and Enhanced (9.75GHz) 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 22kHz to change the band. "Dual LNB" or "Monobloc LNB"
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| 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. Normally used on an 80cm dish to receive Astra at 19.2'E and Hotbird at 13'E (but not simultaneously). |
monobloc setup 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 (22kHz) 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.
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| "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 22kHz o/off respectively. |
This LNB is used with the new Sky Digiboxes 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 and the other two LNB outputs can go either to two standard Digiboxes or to one other "Sky Plus" Digibox. | 
| "OCTO" LNB
As above but with eight independent outputs. |
"Quattro universal LNB"
This has four fixed outputs and is used only in "head end" I.F. distribution systems 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 outputs, 1 - 4, directly to a receiver unless you want to restrict viewing to just one of the four options. Even if you do, the receiver may not work. It's not a good idea. Use the Quad instead.
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 LNB).
However, a dish which is wider than it is tall will need a special LNB.
