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This paper describes a new 50-Ω primary reference standard for coaxial line impedance measurements from dc to 100 MHz. The standard can be used to calibrate vector network analyzers (VNAs) with type N connectors (7 mm). Fabrication, 3-D electromagnetic simulations, and the characterization of the standard are described. The standard consists of a precision coaxial air line terminated by a 50-Ω resistive load and a shielded open circuit. This device can be considered as a primary reference standard since its input reflection coefficient Γ is traceable via dimensional and dc electrical measurements to the International System of Units. Comparison of measurement results and uncertainties obtained with a commercial 50-Ω load, an air line standard, and the primary 50-Ω load is shown.