A low noise block-downconverter is the receiving device of a parabolic satellite dish antenna of the type commonly used for satellite TV reception. The device is sometimes called an LNA (for low noise amplifier), LNC (for low noise converter) or even LND (for low noise downconverter) but as block-downconversion is the principal function of the device, LNB is the preferred term, although this acronym is often incorrectly expanded to the incomplete descriptions, low noise block or low noise block converter.
It is functionally equivalent to the dipole antenna used for most terrestrial TV reception, although it is actually waveguide based. Inside the LNB waveguide a metal pin, or probe, protrudes into the waveguide at right angles to the axis and this acts as an aerial, collecting the signal travelling down the waveguide.
The LNB is usually fixed on the satellite dish framework, at the focus of the reflector, and it derives its power from the connected receiver, sent “up” the same cable that carries the received signals “down” to the receiver. The corresponding component in the transmit link uplink to a satellite is called a Block upconverter (BUC).