Matching Technique Using 50 and 75 Ohm Cables for Resistive Loads

This resource presents a technical method for impedance matching resistive loads below 50 ohms to a 50-ohm transmission line. The technique utilizes series sections of 50-ohm and 75-ohm coaxial cables. The document provides graphical data for determining the required cable lengths (L1 and L2, expressed in wavelengths) to achieve a match for load impedances between 22.2 ohms and 45 ohms. A specific example demonstrates matching a 25-ohm Yagi antenna at 50.150 MHz using RG-58C/U (50 ohms) and RG-59B/U (75 ohms) cables, both with a velocity factor of 66%. Calculated physical lengths are provided in centimeters and inches. The resource also briefly discusses integrating a balun at the load end, suggesting coiling a cable section or using ferrite beads for a W2DU-type balun. This methodology is applicable for feeding vertical and Yagi antennas.