Signal processing
Signals and noise. This section is under construction
The basic purpose of signal processing is to try to retrieve a useful signal from all the noise. At radio frequencies there is noise coming from all kinds of sources, mainly from man-made devices such as car ignitions, electrical switching circuits and of course terrestial radio transmissions.
So the problem for radio astronomers is how to sift through all those radio signals to pick out the signals that have come from beyond Earth.