Aviation (or other) band GP antenna. I needed an installable aviation band antenna, for which I chose the ground plane antenna. I determined the wire lengths for the appropriate frequency in an online calculator. I designed a core that holds the antenna's legs together, which are made of 6x4mm aluminum tube. I drilled an M5 thread into the end of the pipes and connected the wires here, which are connected to the BNC connector screwed to the lower half of the middle part. The three parts are held together by 4 M4x40mm screws, the clamp fits on an 18mm pipe and the coax cable runs through it. It is worth connecting the BNC connector during assembly, or you can even omit it and connect the coax cable permanently. I printed from Petg.