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NETSAT HELP What is an LNB (Low-noise block downconverter) & Types Of LNB'S
01-11-2013, 08:44 PM
Post: #1
What is an LNB (Low-noise block downconverter) & Types Of LNB'S
What is an LNB (Low-noise block downconverter) & Types Of LNB'S


C BAND LNB
========
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KU BAND LNB
=========
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What is an LNB (Low-noise block downconverter)
============================
A low-noise block downconverter (or LNB) is the receiving device on an antenna, for example a satellite dish commonly used for satellite TV reception. Also called a low-noise block,LNC (for low-noise converter), or even LND (for low-noise downconverter), the device is sometimes wrongly called an LNA (low-noise amplifier).

The LNB is a combination of low-noise amplifier, frequency mixer, local oscillator and IF amplifier. It receives the microwave signal from the satellite collected by the dish, amplifies it, downconverts the block of frequencies to a lower block of intermediate frequencies (IF), so the signal can be carried to the indoor satellite TV receiver using relatively cheap coaxial cable. Transferring the signal from the antenna indoors at its original microwave frequency would require an expensive and impractical waveguide.

The LNB is usually suspended on one or more short booms, or feed arms, in front of the dish reflector, at its focus (although some dish designs have the LNB on or behind the reflector). The microwave signal from the dish is picked up by a feedhorn and is fed to a section of waveguide. In this waveguide a metal pin, or probe, protrudes into the waveguide at right angles to the axis and this acts as an antenna, and feeds the signal to a printed circuit board inside the LNB's shielded box for procesing. The lower frequency IF output signal emerges from a socket on the box to which the coaxial cable connects.

LNBF disassembled (All Parts). The waveguide carrying the microwave radio signal collected by the dish passes through the hole in the center. The pins visible at the top and left side of the hole project into the waveguide and receive the signal, converting it to radio frequency alternating currents which are processed by the circuit board.
The LNB gets its power from the receiver or set-top box inside the house. This phantom power is sent "up" the same coaxial cable that carries the received signals "down" to the receiver.
A corresponding component, called a block upconverter (BUC), is used at the satellite earth station (uplink) dish to convert the band of television channels to the microwave uplink frequency.

Some More Facts
============

Amplification and noise
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The signal received by the LNB is extremely weak and it has to be amplified before downconversion. The low noise amplifier section of the LNB amplifies this weak signal while adding the minimum possible amount of noise to the signal.


Block downconversion
--------------------
Satellites use comparatively high radio frequencies (microwaves) to transmit their TV signals. As microwave satellite signals do not easily pass through walls, roofs, or even glass windows, satellite antennas are required to be outdoors.

C-Band: IF frequency = local oscillator frequency - received frequency
Ku-Band: IF frequency = received frequency - local oscillator frequency


LNBFs
-----
With the launch of the first DTH broadcast satellite in Europe (Astra 1A) by SES in 1988, antenna design was simplified for the anticipated mass-market. In particular, the feedhorn (which gathers the signal and directs it to the LNB) and the polarizer (which selects between differently polarized signals) were combined with the LNB itself into a single unit, called an LNB-feed or LNB-feedhorn (LNBF), or even an "Astra type" LNB. The prevalence of these combined units has meant that today the term LNB is commonly used to refer to all antenna units that provide the block-downconversion function, with or without a feedhorn.

Polarization
-----------
Satellite TV signals are usually broadcast using alternating polarization to maximise the number of transmissions carried in a given frequency range as reception equipment can distinguish between transmissions using the same frequency but different polarization. Throughout the World, most satellite TV transmissions use vertical and horizontal linear polarization but in North America, DBS transmissions use left and right hand circular polarization. Within the waveguide of a North American DBS LNB a slab of dielectric material is used to convert left and right circular polarized signals to vertical and horizontal linear polarized signals so the converted signals can be treated the same.


Courtesy - Wikpedia

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01-11-2013, 08:52 PM
Post: #2
RE: What is an LNB (Low-noise block downconverter) & Types Of LNB'S
Internal Electronics Circuit Of A LNB

Electronic Circuit of KU BAND LNB
========================
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Electronic Circuit of C BAND LNB
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01-11-2013, 09:02 PM
Post: #3
RE: What is an LNB (Low-noise block downconverter) & Types Of LNB'S
Nice update
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01-11-2013, 09:37 PM
Post: #4
RE: What is an LNB (Low-noise block downconverter) & Types Of LNB'S
Outer Look Of Lnb's
===============
C Band Lnb
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Ku Band Lnb
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Use of LNB & Supported Dish Antennas
==========================
Ku Band LNB With Dish Antenna
-----------------------------
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C band LNB With Dish Antenna
------------------------------
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