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Low Noise Block (LNB) Primer

The LNB (Low Noise Block) converter is used to improve satellite TV reception. Since satellites operate at high frequencies, it's important to control noise prior to signal processing. A LNB helps prevent degradation of the overall sound and picture quality of satellite TV, eliminating a need for a large dish reflector.

The LNB is a small box which generally attaches to the end that extends from your satellite dish, facing the parabolic reflector (aka, the dish). The dish focuses signals from a satellite 20,000 miles away into the feed horn of the LNB. The LNB receives the signal from the satellite, converts the signal to a lower frequency, and transmits the signal through your coax cable. Your satellite receiver receives the signal and transmits it to your television.

The LNB can amplify and convert a wide band — or 'block' — of frequencies, which helps compensate signal loss at higher frequencies that often occur with coaxial cable. The LNB converts the higher block of microwave frequencies received from the satellite (usually in the range 4 GHz to 21 GHz) that are being down-converted to a lower block range of frequencies for the receiver.

Universal LNBs

A universal LNB can receive both polarizations and the full range of frequencies in both the Ku and C satellite band. Some LNBs can receive both polarizations simultaneously through two different connectors, while other LNBs have either switchable or adjustable polarization.

Typical Universal LNB specifications:

• Local Oscillator (LO): 9.75 GHz /10.6 GHz
• Frequency: 10.7 GHz-12.75 GHz
• Noise Figure (NF): 0.7 dB
• Polarization: Linear

Standard DBS LNB:

• Local Oscillator (LO): 11.25 GHz
• Frequency: 12.2 GHz-12.7 GHz
• Noise Figure (NF): 0.7 dB
• Polarization: Circular

Typical North American C-band LNB specs:

• Local Oscillator (LO): 5.15 GHz
• Frequency: 3.6-4.2 GHz
• Noise Figure (NF): 15 to 100 Kelvins (uses Kelvin ratings as opposed to dB rating)
• Polarization: Linear

Dual and Quad LNBs are multiple LNBs contained in one package, which allows you to use multiple receivers with one dish.

A Dual LNB consists of two universal LNBs, attached at a slightly offset angle in a single housing. A Dual LNB uses only one "F" connector and coaxial cable connection to the converter box. Don't attempt to split the feed from one LNB to two tuners. Use an LNB with multiple outputs.

The Monobloc LNB — which is also a Dual LNB system — has only one output, so you can only view one satellite transmission at a time. Dish systems which have two or more separate LNBs that are each connected to separate receivers allow you to view and record both transmissions simultaneously. The Monobloc LNB is specifically designed to receive signals from satellites that are close in space.

Other LNB variations include a Quad Universal LNB (Quad-Output LNB), which can accommodate four separate receivers. The Octo LNB has has 8 independent outputs and can accommodate eight separate receivers.

In general, any standard universal LNB will work with any circular prime focus dish or offset focus dish. An offset focus dish appears circular to the LNB, even though it's actually taller than it is wide. But dishes that are wider than they are tall require a special LNB.

It's critical to purchase weather-resistant LNBs to prevent oxidation and corrosion, which ultimately will lead to signal degradation.

When installing your LNB, make sure that both the outer and inner conductors make solid contact. High resistance can cause the LNB to permanently switch into a state of low voltage, which will ultimately result in overall satellite signal degradation.