A low-noise block converter (LNB, for low-noise block, or sometimes LNC, for low-noise converter) is the (receiving, or downlink) antenna of what is commonly called the parabolic (actually paraboloid) satellite dish commonly used for satellite TV reception. It is functionally equivalent to the dipole antenna used for most other TV reception purposes, although it is actually waveguide based. Whereas the dipole antenna is unable to adapt itself to various polarization planes without being rotated, the LNB can be switched electronically between horizontal and vertical polarization reception. The LNB is usually fixed on or in the satellite dish, for the reasons outlined below. The corresponding component in the uplink transmit link is called a Block upconverter (BUC).
Satellites use comparatively high radio frequencies to transmit their signals.