Yagi Antenna Fixtures

thingiverse

To build a Yagi antenna, you need a dipole as the driven element, a reflector and one or more directors. Creating a holder for both the dipole driven element and the reflector/director that fits on a 3/4" non-conductive tube is essential. The dipole holder is designed to accommodate 1/8" material with a separation between sides of the dipole of 2mm, providing a cavity to hold solder joints from the coax (RG6) connection. A top cap held in place by 1 inch 6-32 screws adds extra strength to the structure. To achieve optimal performance, silicone sealant is used to fill internal voids and surface gaps between components, minimizing moisture contamination. Screws holes and antenna grooves are also sealed with sealant for added protection. The reflector/director holder features a simple 1/8" through hole where required material length is held at its center. A countersunk hole in the bottom of both dipole and R/D holders serves as an anchor point to secure the unit to the correct position on the antenna shaft. Materials used include two sections of 1/8" brass for the driven element, and 1/8" aluminum for the reflector/director, sourced from a welding supply store. The Yagi antenna was built for a frequency of 390 MHz, but a similar design has also been successfully implemented at 435MHz (UHF HAM band) using YagiCad by VK3DIP as a starting point. Tuning with a Vector Network Analyzer is highly recommended to achieve optimal results. The constructed antenna boasts an impedance of 52 ohms, -5 ohms reactance, and a SWR of 1.13. Simulation predicts a gain of 7.5dBi, although verification in the field has yet to be performed.