Are LNBs As Important As They Appear To Be?

In the world of satellite communication, a lot depends on the proper transmission and reception of signal. LNBs are critical to amplify the received satellite signal with minimal noise contribution.

Low-Noise Block down Converter

A low-noise block down converter comprises of a receive-only amplifier and down converter mounted on the satellite dish. There are many individual components in a low-noise block down converter,including a low-noise amplifier, frequency mixer, local oscillator and intermediate frequency amplifier. The low noise block converter gets the power from the receiver or set-top box via the coaxial cable that carries the signals from the LNB to the receiver.

The Working of an LNB

The low-noise block down converter works in the following way:

– The dish receives the satellite signal – The LNB amplifies the signal – The signal is then down converted to a lower block of intermediate frequencies. In this process, the signal is sent by a low cost coaxial cableto the indoor set top box/DVR or satellite modem.

Why are LNBs Required?

LNBs are mainly used to down convert a block of frequencies to intermediate lower frequencies.

The satellites use high frequency microwave frequencies. The microwave signals are not able to easily pass through walls, roofs or even glass windows. The satellite receive-only dish and LNB are mounted outdoors and the residential set top box or modem, indoors.

Low-Noise Block down Converter Placement

Since the first signal frequency conversion takes place at the satellite dish, the LNB is usually mounted on a short feed arm at the focal point of the reflector (of the dish), or for larger dishes, with a different (egCasegraine) feed, behind the reflector. It is a relatively small unit and is easy to mount onto the waveguide feed of the dish. This placement allows the LNB to receive the microwave signal via the feed and waveguide interface flange.

The microwave signals received by satellite dish use the low-noise block down converter to convert the received (from satellite) signal to a lower IF frequency for simple low cost connection via coaxial cable to the residential set top box or receiver/DVR or satellite modem thus simplifying (at lowest cost) the entire communication system.