440 MHz 4 Element Yagi

thingiverse

This is a four-element Yagi antenna designed for operation on the 440 MHz frequency band. To create this design, an initial SCAD document has been prepared to parameterize the spacing between elements. However, it's essential to note that there's a limitation to the frequency range that this SCAD document can handle - don't use frequencies higher than 440 MHz as it will render calculations invalid. There is also another critical note: customizers may not work with the parametric SCAD file. In this case, users need to edit the part through OpenSCAD at the time of making any modifications. Should there be changes to this, the relevant information in this note may also be subject to alteration. Assembly Instructions: This project comprises three key components, totaling five printed parts: (1) 440Element_End.stl (2) 440Element_Segment.stl (3) 440Element_Mount_Tap.stl It's recommended to print these parts with a 0.300 mm layer height and an infill of 20% {seen in the accompanying image}. After printing all necessary pieces, insert the notch connector into the end segment and securely tap it together with a hammer - avoid hitting them too hard as they will likely break apart. Instead, use gentle taps until they click firmly. The recommended assembly order is depicted in AssemblyOrder.png: Segment > Mount_Tap > Segment > End Specific element lengths are given below: - Reflector Segment: {13.27 inches | 337.058 mm} - Driven/Mount_Tap Segment: {12.87 inches | 326.898 mm} - Director 1 Segment: {11.915 inches | 302.641 mm} - Director 2/End: {11.915 inches | 302.641 mm} A crucial aspect of this assembly process is working with the Mount_Tap section - particularly for those who may be unfamiliar with Yagi antennas. The element does not pass through its entire support. What was done here was to bend one end of the hanger slightly and then insert it through a side hole on the segment, pushing it down using a wood screw. One wire {center or ground} from the coax cable should then be attached to this screw, after which it's tightened securely to make one tap - repeating the process on the other side creates a secure connection. Once taps are in place, measure and cut wire hangers for each element - except the Mount_Tap section - leaving a small bend at the midpoint of the element length. Next, push each hanger through its support until there's an equal amount of exposed wire on both sides of the segment hole - this is secured by the bend, which prevents any further shifting during use. Before transmitting with this antenna for the first time, always test it using an SWR meter to ensure accurate operation - failing to do so may result in damage to a home-built transmit amplifier.