A low noise amplifier (LNA) is typically the first active component in a radio receiver chain. Its job is to take a microscopic signal captured by an antenna and amplify it enough for the rest of the circuit to process. Because any noise introduced at this first stage will be multiplied by all subsequent amplifiers, an LNA is carefully designed with specialized transistors and impedance matching to keep its noise figure as close to zero as possible.
The LNA is mounted directly on the dish antenna to avoid the signal loss you get from running a long coaxial cable.
Related terms
Amplifier
A circuit or standalone device that increases the power, voltage, or current of an electrical signal.
Gain
A measure of a circuit's ability to increase the power or amplitude of a signal.
Signal processing
The mathematical manipulation of physical data streams to filter, compress, or extract information.