The LNA-LNB At the focal point of the parabola, we go to place the active element itself, or rather an LNA or LNB, but it can be a dipole, a helix or whatsoever you like.

The low noise block converter (LNB for low noise block, or sometimes LNC, for low noise converter) is used inthe reception of satellite TV. These satellites use relatively high radio frequencies to transmit their signals. As the microwave signals from satellites do not pass easily through walls, roofs and glass windows, satellite antennas are mounted on the outside, and the signal must be transmitted within a cable. When radio signals are transmitted by cables, the higher the frequency the higher are the losses in the cable per unit length. The sig - nals used for satellite are on a high frequency (in gigahertz) and therefore one must use special cables (expen - sive) to minimize line losses.

The job of the LNB is to use the superheterodyne principle and take a wide block (or band) of relatively high frequencies, to amplify and convert them to similar signals but on a much lower frequency (called intermediate frequency or IF ). These frequencies pass through a cable with much less attenuation of the signal. It is there - fore much easier and less costly to design electronic circuits to operate at these lower frequencies (rather than very high frequencies of satellite transmission).