The PA 303 N preamplifier was designed for the amplification of measuring signals, e.g. weak signals of near-field probes with high resolution. The PA 303 N is to be used with the 50 ohm input of a spectrum analyzer or an oscilloscope and is powered by the wall-plug transformer. With the correct cable a near-field probe can be connected to the input of the preamplifier. The input and the output of the PA 303 N use N connectors.