Low Noise Blocks LNB's

An LNB is a device mounted on the dish, designed collect and amplify the satellite signals and convert them from a high frequency to a lower frequency. LNBs can be controlled to receive signals with different polarisation (horizontal and vertical). The signals can then be carried down the cable cable to a satellite receiver.

An LNB can be either single (one output), Twin (two outputs), Quad (four outputs), Quatro (four outputs), or Octo eight outputs).

A Twin LNB would be required when more than one receiver (or a PVR like Sky+) is used allowing the viewing of different channels on two independent satellite receivers.

A Quad LNB would be required when more than three receivers.

A Quatro LNB would be required when requiring to install a multiswitch system that can provide feeds for many receivers, as in the case of a community system installation.

Here is an example of a Universal LNB for smaller 80cm offset dishes.

Here are examples of the Invacom LNB's used for Prime Focus big dish installations.

Monobloc LNBs

A monobloc LNB (also spelled "monoblock") is a unit consisting of two LNBs and is designed to receive satellites spaced close together, generally 6 degrees. For example in parts of Europe monoblocs designed to receive the Hot Bird (13E) and Astra 1 (19E) satellites are popular because they enable reception of both satellites on a single dish without requiring an expensive and noisy motor.

Low noise block converters operate in extremes of temperature and humidity, and although they generally have a very low failure rate they do not last forever. Some fail as they get older, others suffer a drop in performance, resulting in poor picture quality.

Feedhorns

Some LNBs, particularly the Invacoms mentioned above require a feedhorn preferably one from the manufacturer of the LNB, has to be attached to the LNB.

The most common type of feedhorn manufactured today is called a scalar feedhorn. This type of feed has a large circular plate with a series of three or four concentric rings attached to its surface. The scalar rings conduct the incoming signal from the outer edges of the focal cloud to the large waveguide opening located at feed centre. The scalar feedhorn primarily sees or illuminates the inner portion of the antenna's surface area, while attenuating the signal contribution from the outer portion of the dish by 8 to 22 dB, depending on whether the dish is deep or shallow in its construction.

Inline Amplifiers

Inline amplifiers will not increase your weak Astra 2D signals, in fact they will probably reduce your signal. An Inline Amplifier should be used when the cable run from the LNB to the receiver exceeds 75 - 100 feet; install the amplifier between the LNB and the Multiswitch or satellite receiver. Inline amplifiers are powered by the voltage already present on the satellite signal coax. If your signal is not strong enough in the first place, you are really only amplifying noise. An Inline amplifier is unfortunately of little or no use when trying to increase a weak signal, it will also 'boost' stronger signals swamping your already weak signal. A better LNB or larger dish will give far better results.