LNB (Low Noise Block Down Converter) A device mounted on the dish, designed to 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.

The television signals can then be carried by a double-shielded aerial cable to the satellite receiver while retaining their high quality.

A universal LNB is the present standard version, which can handle the entire frequency range from 10.7 to 12.75 GHz and receive signals with both vertical and horizontal polarisation. The most commonly used LNB is actually called LNBF, the F standing for Feedhorn (inbuilt).

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 is used, allowing the viewing of different channels on two independent satellite receivers. Twin output LNBs are required for Freesat+ and Sky+HD receivers, allowing you to record two programmes at the same time, or record one while watching another.

Low noise block converters have a hard life; they 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, replacing an old LNB could improve reception.