Uncertainty of reproduction of units of wave resistance and angle of phase shift by a section of coaxial line

For measuring of S parameters of two-port networks in coaxial waveguides, a wide distribution was received by automatic network analyzers calibrated by devices which are standards of the value of units of measurands. The wide distribution for calibrations was received by a section of precision coaxial air dielectric line (air line) with the given parameters. In particular, the basic element of reproduction of units of wave resistance (UWR) and angle of phase shift (UAPS) and transmission of their sizes in the national measurement standard UWR in coaxial waveguides and in national installation of high accuracy of UAPS in coaxial waveguides is an air line. The improvement of a model of a real air line is discussed.